5 - Poster session Poster presentation 006 Electric field tuning of intervalley tunneling in silicon double quantum dots JC Abadillo-Uriel1, MJ Calderón1, S. N. Coppersmith2, M. Friesen2 1Instituto de Ciencia de Materiales de Madrid, MADRID, Spain 2University of Wisconsin-Madison, MADISON, United States of America Confined electrons in silicon quantum dots are promising candidates for quantum computation. The valley physics in this system is strongly affected by disorder at a Si/SiGe quantum well interface, which in turn affects our ability to control qubits. Indeed, single-atom disorder at the interface can create valley mixing and valley-orbit hybridization effects. In a double dot, it can cause intervalley tunneling. In this work, we use a tight-binding approach to analyze the tunnel coupling in a single-electron double quantum dot with interfacial disorder, between the ground state of one dot to the two lowest valley states of the second dot. We find that the presence of atomic disorder at the interface can disturb the phase of the localized valley states, and as a function of the vertical electric field we find that the difference in amplitudes of these couplings can change sign. Moreover, in certain cases, the tunnel coupling to one of these states can be completely suppressed, providing opportunities for very high-fidelity qubit initialization and readout. 5 - Poster session Poster presentation 096 Characterization of 28Si:77Se+ spin system as a candidate for incorporation into optical cavity-QED structures R.A. Abraham1, K.M. Morse1, L.B. Bergeron1, A.D. DeBreu1, N..A. dr. Abrosimov2, M.T. dr. Thewalt1, S.S. dr. Simmons1 1Simon Fraser University, BURNABY, Canada 2Leibniz Institute for Crystal Growth, BERLIN, Germany Isotopically purified 28Si offers a zero-nuclear-spin environment where donor impurities experience a 'semiconductor vacuum'. Long coherence times and high manipulation fidelity have made substitutional donors in 28Si promising canditates for large-scale quantum networks.Optical transitions in 28Si:77Se+ offer several advantages over the more usual shallow donor candidates. In its singly-ionized form this chalcogen double donor has a hydrogenic orbital structure and a large 1sA binding energy of 593 meV. Thus 77Se+ has easily accessible mid-infrared optical transitions to orbital excited states not offered by group V donors such as 31P, which have much smaller 1sA binding energies. Additionally, transitions to the first excited state of this system are sufficiently narrow to be spin selective in earth's magnetic field. In the absence of an applied magnetic field, the singlet and triplet hyperfine states of 1sA are split by A = 1.67 GHz. Here we characterize the 28Si:77Se+ spin system to gauge its suitability for incorporation into optical cavity-QED structures. 5 - Poster session Poster presentation 032 Emergence of chaos from a quantum system using a single nuclear spin SA Asaad1, V. M. dr. Mourik1, H. F. Firgau1, C. A. H. dr. Holmes2, G. J. M. prof. Milburn2, J. M. a/prof McCallum3, A. Morello1 1University of New South Wales, SYDNEY, Australia 2University of Queensland, BRISBANE, Australia 3University of Melbourne, MELBOURNE, Australia

Since the discovery of chaotic behaviour, many of its fascinating properties have been discovered, and its effects have been found in a diverse range of fields. While chaos has been studied in depth in classical dynamics, the crossover to its equivalent quantum system has been given far less attention. Contrasting classical chaos, the quantum system displays quasi-periodicity, localisation, and tunneling through classically forbidden regions of phase space. The discrepancy between these two regimes is striking, and raises major questions concerning the emergence of chaos from an essentially quantum world. Our project aims at studying a single-atom quantum system, whose dynamics are equivalent to a classical chaotic system, namely that of a periodically-driven non-linear top. We base our system on our usual Phosphorus donor qubit in purified 28-Si, but replace the donor with an Antimony isotope, 123-Sb, which has a nuclear spin of 7/2. The resulting effect is twofold: an increase of the nuclear spin Hilbert space, and the addition of the nuclear quadrupole interaction, which is quadratic in nuclear spin operators. We further add a periodic drive, resulting in a quantum equivalent system of the periodically-driven non-linear top, a classically chaotic system. Our system’s record-long coherence times, and high-fidelity single-shot readout, as observed in 31-P donors, allow us to accurately study the dynamics of the quantum system. We shall give a detailed explanation of our upcoming experiment, possibly with some initial measurements, along with a theoretical background and simulations of the classical and quantum regimes. This will show us the similarities and differences between the two approaches, giving us key insights into the emergence of chaos. 5 - Poster session Poster presentation 092 Coherent spin-exchange via a quantum mediator TA Baart1, T Fujita1, C Reichl2, W Wegscheider2, LMK Vandersypen1 1Delft University of Technology, DELFT, The Netherlands 2ETH Zurich, ZURICH, Switzerland Coherent interactions at a distance provide a powerful tool for quantum simulation and computation. The most common approach to realize an effective long-distance coupling 'on-chip' is to use a quantum mediator, as has been demonstrated for superconducting qubits and trapped ions. For quantum dot arrays, which combine a high degree of tunability with extremely long coherence times, the experimental demonstration of coherent spin-spin coupling via an intermediary system remains an important outstanding goal. Here, we use a linear triple-quantum-dot array to demonstrate a first working example of a coherent interaction between two distant spins via a quantum mediator. The two outer dots are occupied with a single electron spin each and the spins experience a superexchange interaction through the empty middle dot which acts as mediator. Using single-shot spin read-out we measure the coherent time evolution of the spin states on the outer dots and observe a characteristic dependence of the exchange frequency as a function of the detuning between the middle and outer dots. This approach may provide a new route for scaling up spin qubit circuits using quantum dots and aid in the simulation of materials and molecules with non-nearest neighbour couplings such as MnO, high-temperature superconductors and DNA. The same superexchange concept can also be applied in cold atom experiments. 5 - Poster session Poster presentation 080 What can we do with a singlet-triplet qubit coupled to a nuclear spin qubit? ADB Baczewski1, JKG Gamble1, NTJ Jacobson1, RPM Muller1, EN Nielsen1, PHC Harvey-Collard2, MSC Carroll1 1Sandia National Laboratories, ALBUQUERQUE, United States of America 2Universite de Sherbrooke, SHERBROOKE, Canada Recent experiments have demonstrated the possibility of coherently coupling a quantum dot in silicon to a nearby 31P donor [1]. It is possible to encode two qubits in the state of this complex, one in the electronic spin configuration of the quantum dot, and another in the nuclear spin state of the donor. Universal two-qubit control can be realized through a combination of electrical control of the detuning between different donor-dot charge states, and NMR control of the

donor nuclear spin. However, it is expected that the gate times associated with NMR operations may meet or exceed the T2

* of the qubit encoded in the electronic spin configuration. We will address what it is that we can do with this encoding in spite of this perceived limitation. We will discuss two different modes of operation - one in which the nuclear spin qubit is used as a local memory for the state of the electronic qubit, and another in which coupling between pairs of these complexes can be used to efficiently make joint measurements of the nuclear spin qubits. Sandia is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy’s National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. [1] P. Harvey-Collard, et al., arXiv:1512:01606 5 - Poster session Poster presentation 066 Strategy for 3D quantum computer fabrication using minimal STM patterning operations and interlayer alignment J.B. Ballard, J. H. G. dr. Owen, S. W. dr. Schmucker, J. N. dr. Randall Zyvex Labs, RICHARDSON, United States of America Promising results have been demonstrated for phosphorus in silicon qubit devices using a 2-D geometry with the critical fabrication performed using hydrogen depassivation lithography (HDL). Scaling up beyond four or five qubits appears difficult due to the crowding of support features such as gates and electrodes. To overcome this, a feasible 3-D architecture was proposed using a cross-bar type geometry with a lower control (LC), qubit (Q), and upper control (UC) layers.1 Still, there are significant fabrication challenges to achieving working devices. Basic 2-D device fabrication includes surface preparation of Si(100)-H, patterning with HDL, deposition of PH3, P incorporation, and epitaxial overgrowth.2 This may be extended to three dimensions by stacking HDL patterned LC, Q, and UC layers with epitaxial layers between. Due to the multi-layer structure with the second layer requiring the highest precision patterning, tip wear during LC layer patterning may limit the quality of Q layer patterning. Also, this 3-D geometry requires tight precision for interlayer alignment. It has been shown that buried layers can be visualized by capacitance microscopy among other methods, but not with the required precision to fabricate these devices. 3 This work describes an alternate fabrication concept that may limit tip-based patterning and enhance the capability to align between layers. First, a delta layer with universal P incorporation and a thin (~2-5nm) layer of epitaxial overgrowth is fabricated in part A. Next, lithography either using tip based hard mask deposition4 or nano-imprint lithography defines the control lines of the LC layer (part B). Low temperature sample prep removes the mask layer (part C), followed by epitaxial overgrowth, HDL patterning, and P incorporation (part D). The topography from the lithography will guide placement of the SET and qubit relative to the LC lines. Following epitaxial overgrowth, parts A-C may be repeated to produce the UC layer. Design and fabrication limitations will be discussed as well as potential roadblocks to using this fabrication method, especially related to low-temperature sample prep and the influence of topography. Hill, C. et al. Sci. Adv. 1-15 (2015). Ruess, F. J. et al. Small 3, 563-567 (2007). Rudolph, M. et al. Appl. Phys. Lett. 105, 163110 (2014). Ballard, J. B. et al. JVSTB 32, 041804 (2014). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286080_OZjzJ2AOIF.png Caption 1: Figure Caption: Possible process flow for topographic multilayer qubit alignment 5 - Poster session Poster presentation 014 Characterization of vibration-induced electrical noise in a cryogen-free dilution refrigerator D.B. Bar University of New South Wales, KENSINGTON, Australia

In this poster, we investigate the effect of the vibrational noise of a pulse tube cooler on low-temperature quantum measurements. We characterize the noise spectrum, test different types of cables for their sensitivity to triboelectric noise, and quantify the effect of pulse tube vibrations on the coherence time of an electron spin qubit. In recent years, cryogen-free low-temperature dilution refrigerator setups (dry fridges) have been gaining presence in experimental science. Dry fridges posses the advantage of convenient operation, and cut down on helium costs compared to wet dilution refrigerator setups which entail significant helium losses and complex peripheral reliquefication infrastructure. In addition, wet fridges cannot accommodate large sample spaces due to the use of narrow-neck dewars to reduce boil-off and helium refill frequency. However, to achieve above advantages, dry fridges employ pulse tube cryocoolers which induce vibrational noise. While manufacturers make serious attempts to isolate the pulse tube’s vibrations from the sample space in the cryostat, the problem is not fully solved and vibrational noise is still present. In this poster, we characterize the mechanical vibrations in a BlueFors dilution refrigerator and investigate how they can affect our measurements. The dominant noise is found to be in the 5-10 kHz range and the noise magnitude depends strongly on the temperature. We test the effect of different cables on the noise to learn about the noise sources and reduce it. Triboelectrics is found to be the main mechanism by which noise couples vibration to the electrical signal. Reducing the noise level by over an order of magnitude is achieved by reducing cables movement, flattening semi-rigid cables, and jacketing flexible cables . Furthermore, we study and characterize the effect of the pulse tube’s vibration on an electron spin qubit mounted on this dry fridge setup. Mechanical vibrations lead to dephasing in quantum experiments by producing motion in inhomogeneous external magnetic fields [1] or by inducing voltages into the control lines connected to the device. We map out the noise spectrum coupled to the electron spin qubit using coherence time measurements, and find that the spectral components measured match the pulse tube’s spectral fingerprint. Finally, we observe a 2.5x improvement in the qubit's Hahn echo coherence time when the pulse tube is temporarily switched off. [1] - J. Britton, J. Bohnet, J. Bollinger, B. Sawyer, H. Uys, and M. Biercuk, arXiv:1512.00801 (2015). 5 - Poster session Poster presentation 095 Quantifying the Effect of Charge Noise Defects on Silicon Quantum Dots EIB Barker1, NAB Baker2, JW Webster2, NMN Nichols2, BJP Palmer2, GKS Schenter2, MGW Warner2 1PNNL, KENNEWICK, WA, United States of America 2Pacific Northwest National Lab, RICHLAND, United States of America The voltage-current relationship in a silicon double quantum dot can be used for characterizing the quantum dot device. Studying this relationship gives insight into how errors and small variations in input voltage affect performance, as well as how it is affected by donor electrons from material impurities and charge defects. Our current working models of the system use a finite element framework solving a coupled Poisson-Schrodinger equation to determine the voltage and current within the device. Single charge defects at specific locations are added to the system to determine their effect on the predicted voltage-current relationship. Given experimental measurements, inverse modeling can be used to determine the likely location and magnitude of a charge defect as well as to explore the sensitivity to initial parameters of the forward model. Probabilistic Collocation methods are being utilized for this uncertainty quantification and inverse modeling. 5 - Poster session Poster presentation 081 Classical Computation by Quantum Bits S Bose1, B Antonio1, W. K. Hensinger2, J. Randall2, G. W. Morley3 1University College London, LONDON, United Kingdom 2University of Sussex, BRIGHTON, United Kingdom 3University of Warwick, COVENTRY, United Kingdom

Atomic-scale logic and the minimization of heating (dissipation) are both very high on the agenda for future computation hardware. An approach to achieve these would be to replace networks of transistors directly by classical reversible logic gates built from the coherent dynamics of a few interacting atoms. As superpositions are unnecessary before and after each such gate (inputs and outputs are bits), the dephasing time only needs to exceed a single gate operation time, while fault tolerance should be achieved with low overhead, by classical coding. Such gates could thus be a spin-off of quantum technology much before full-scale quantum computation. Thus motivated, we propose methods to realize the 3-bit Toffoli and Fredkin gates universal for classical reversible logic using a single time-independent 3-qubit Hamiltonian with realistic nearest neighbour two-body interactions. We also exemplify how these gates can be composed to make a larger circuit. We show that trapped ions may soon be scalable simulators for such architectures, and investigate the prospects with dopants in silicon. 5 - Poster session Poster presentation 101 Towards higher temperature and scalable architecture in silicon MOS spin qubits J.M. Boter1, G. Droulers1, S.V. Amitonov2, F. Mueller2, F.A. Zwanenburg2, M. Veldhorst1, L.M.K. Vandersypen1 1QuTech, DELFT, The Netherlands 2MESA+ Institute for Nanotechnology, University of Twente, ENSCHEDE, The Netherlands Silicon is an excellent host for spin qubits, which is one of the most promising platforms for large-scale quantum computing. First, silicon has a low fraction of nuclear spins, which can be further reduced by purification, increasing the coherence times by factors of 100 to 10 000 compared to GaAs. Second, silicon can potentially rely on conventional semiconductor technology, capable of constructing billions of transistors on a single chip. A crucial aspect in creating extendable structures for large-scale quantum computing, is the integration of classical electronics. A major advance would be if qubit operation can be at elevated temperatures. Here we discuss the four-Kelvin qubit, which we believe can be realized using the silicon-MOS platform. Isolated spin states can be obtained by lifting the valley degeneracy and realized via quantum confinement and vertical electrical fields. In particular the Si-MOS system enables large valley splitting due to the strong confinement at the interface. In combination with a well-considered device design the valley splitting can be increased to the meV range. We will discuss the techniques and operation methods to work at higher temperature. To scale to the required two-dimensional qubit arrays for large-scale quantum computing, we explore industry-compatible fabrication processes that can go beyond the currently realized 1D quantum dot arrays. Fabrication will focus on vertical interconnects to address central dots in 2D architectures. We have developed a novel method to characterize the fabrication processes, including a parallel quantum-point-contact (QPC) array to study reproducibility of device characteristics, such as the gate pinch-off voltage. We aim for 2x2 and 3x3 quantum dot arrays in a fully vertical and scalable architecture. IV - Session IV: Quantum dots and nanowires Oral presentation 082 Anisotropic Pauli spin blockade in hole quantum dots M Brauns1, J Ridderbos1, A. Li2, E.P.A.M. Bakkers2, F.A. Zwanenburg1 1University of Twente, ENSCHEDE, The Netherlands 2Eindhoven University of Technology, EINDHOVEN, The Netherlands We present measurements on gate-defined double quantum dots in Ge-Si core-shell nanowires, which we tune to a regime with visible shell filling in both dots (Fig. 1a). We observe Pauli spin blockade (Fig. 1b, c) and can assign the measured leakage current at low magnetic fields to spin-flip cotunneling, for which we measure a strong anisotropy related to an anisotropic g-factor. At higher magnetic fields we see signatures for leakage current caused by spin-orbit coupling between (1,1)-singlet and (2,0)-triplet states. Taking into account these anisotropic spin-flip mechanisms, we can choose the magnetic field direction with the longest spin lifetime for improved spin-orbit qubits.

Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286260_eAPFZ291Dg.png Caption 1: a) Charge stability diagram b) and c) zooms of the marked bias triangle pairs in a) for both bias directions. II - Session II: Single donors and acceptors Oral presentation 071 Controllable Exchange Mediated Two Electron Correlations on Precision Placed Donors in Silicon M. Broome, G dr House, K Gorman, J Hile, J K dr Keizer, T W dr Watson, D K Keith, W B dr Baker, M Y S prof Simmons University of New South Wales, KENSINGTON, Australia This work demonstrates the first important step toward controllable spin-spin interactions between single electrons confined to phosphorus donors in silicon. We use precision placed few donor quantum dots made with STM lithography, where each dot is tunnel coupled to an in plane single electron transistor. Figure 1a shows the lithographic pattern identifying two donor quantum dots with VL and VR gates to measure the charge stability map shown in Fig. 1b. We operate around the (2,0)-(1,1) charge region where electron exchange interactions are expected as a result of the coherent tunnel coupling between the two dots. Using a sequence of pulses we can read the spin state of an electron on each dot in the (1,1) charge state [1,2]. We initialize the electrons in the (1,1) region, after which we pulse along a detuning axis towards the (2,0) charge region (white arrow in Fig. 1c) [3]. As a function of this detuning we observe the onset of the exchange interaction, leading to anti-correlated spins states. In addition, we measure singlet-triplet mixing and determine their associated T1- lifetimes to be of the order 10s of seconds. Our results pave the way towards a coherent two-electron exchange gate in donor based systems. Figure 1: (a) Few donor double-dot patterened by STM lithography. Around the patterned dots are in-plane gates {GL,GM,GR,GS} and a SET charge sensor used for spin readout. (b) Close-up of the lithographic out line of dots L and R which contain 2 and 1 phosphorus donors respectively. (c) Charge stability map showing charge regions of the two donor dots. Spin readout for L and R are performed at the red and blue circles respectively. The exchange interaction is controlled by pulsing along the detuning axis shown by the white arrow. [1] Elzerman, J. M. et al. Single-shot read-out of an individual electron spin in a quantum dot, Nature 430, 431-435 (2004). [2] Buch, H. et al. Spin readout and addressability of phosphorus-donor clusters in Silicon, Nature Communications 4, 2017 (2013) [3] KC Nowack, et al. Single-shot correlations and two-qubit gate of solid-state spins, Science 333 (6047), 1269-1272 (2011). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286087_IrgicAsfcY.jpg I - Session I: Single donors and acceptors Oral presentation 026 Donor wavefunctions in Si gauged by STM images M J CALDERON INSTITUTO DE CIENCIA DE MATERIALES DE MADRID, ICMM-CSIC, MADRID, Spain Single dopant wave functions in Si have recently been probed by scanning tunneling spectroscopy, revealing localized patterns of resonantly enhanced tunneling currents. We show that the shapes of the conducting splotches resemble cuts through Kohn-Luttinger (KL) hydrogenic envelopes, which modulate the interfering Bloch states of conduction electrons. All the non-monotonic features of the current profile are consistent with the charge density fluctuations observed between successive {001} atomic planes, including a counter-intuitive reduction of the symmetry -- a heritage of the lowered point group symmetry at these planes. A model-independent analysis of the

diffraction figure constrains the value of the electron wavevector to k0=(0.82±0.03)(2 π/aSi). Unlike prior measurements, averaged over a sizeable density of electrons, this estimate is obtained directly from isolated electrons. We further investigate the model-specific anisotropy of the wave function envelope, related to the effective mass anisotropy. This anisotropy appears in the KL variational wave function envelope as the ratio between Bohr radii b/a. [1] Authors thank partial support by CNPq, FAPERJ in Brazil, by FIS2012-33521, MINECO in Spain and by ARC CE110001027 and ARO W911NF-08-1-0527 in Australia. [1] A. L. Saraiva, J. Salfi, J. Bocquel, B. Voisin, S. Rogge, Rodrigo B. Capaz, M.J. Calderón, Belita Koiller. Phys. Rev. B 93, 045303 (2016). II - Session II: Single donors and acceptors Oral presentation 031 Exchange coupling in a three-qubit system based on silicon quantum dots KWC Chan1, HCY Yang1, MV Veldhorst1, YW Wang2, RF Ferdous2, JCCH Hwang1, WH Huang1, FM Mohiyaddin1, FEH Hudson1, GK Klimeck2, KMI Itoh3, A. Morello1, R. Rahman2, ASD Dzurak1 1University of New South Wales, KENSINGTON, Australia 2Purdue University, INDIANA, United States of America 3Keio University, TOKYO, Japan Spin-based quantum dot qubits in semiconductors have high potential for scalable quantum information processing [1] due to their relative immunity to electrical noise and compatibility with well-established semiconductor manufacturing. Extremely long spin coherence times are possible in isotopically purified silicon [2], and quantum dot qubits have now been constructed with fidelities that meet certain fault-tolerance thresholds [3]. Our group has recently demonstrated a two-qubit logic gate based on silicon metal-oxide-semiconductor (SiMOS) quantum dots [4], and here we demonstrate the operation of three quantum dot qubits configured in a linear array. The quantum dots are realized in silicon-28, enabling long coherence times [3], and each qubit can be addressed independently due to its gate-voltage tuneable g-factor [3, 4]. We show pairwise two-qubit exchange coupling by demonstrating spin funnels in the electron-spin resonance (ESR) spectra for both nearest neighbour qubits and next-nearest neighbour qubits. The results show that next-nearest neighbour coupling is significantly weaker than the direct exchange coupling. The experiments are supported by atomistic modelling using NEMO. The presence of aluminium-oxide between adjacent gate electrodes significantly reduces the exchange coupling between quantum dots. However, our NEMO calculations also show that increasing the SiO2 gate-oxide thickness leads to an exponential increase in the exchange coupling. Our simulations allow us to determine the optimum coupling required for multi-qubit operation while maintaining long coherence times. We conclude by discussing the relevance of these results to future large-scale quantum processing based on SiMOS quantum dot qubits. [1] D. Loss and D. P. DiVincenzo, Phys. Rev. A 57, 120-126 (1998). [2] K. M. Itoh and H. Watanabe, MRS Comm. 4, 143-157 (2014). [3] M. Veldhorst et al., Nature Nanotech. 9, 981-985 (2014). [4] M. Veldhorst, et al., Nature 526, 410-414 (2015). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285988_vBKFa5lnS7.jpg Caption 1: SEM image, measurement results and NEMO simulation III - Session III: Quantum processor architectures Oral presentation 005 Towards Quantum Dot Qubits at Intel JSC Clarke, VL Le, ABM Mei, DM Michalak, RP Pillarisetty, JR Roberts, NT Thomas, ZY Yoscovits Intel Corporation, HILLSBORO, OR, United States of America

Intel and Delft have entered into a 10yr, $50M partnership to advance quantum computing. Our joint efforts include 1) using Intel’s fabrication facilities to produce silicon quantum dots with improved dot to dot uniformity and repeatability, 2) systematic studies of film growth techniques and patterning to characterize the surface potential of quantum well heterostructures, and 3) establishing a supply chain for isotopically purified Si-28 for improved electron spin coherence time. Collectively, these efforts are expected to result in improved spin qubit performance with a path to deterministic scaling of larger qubit arrays. This talk will introduce Intel’s QC Strategy and engagement with QuTech. Additionally, we present silicon quantum well stack development using CVD deposition of SixGey heterostructures at Intel. Several analytical techniques have been used to characterize the resulting stacks. These include reciprocal space mapping (RSM), Raman spectroscopy, Secondary Ion Mass Spectrometry (SIMS), TEM, SEM, and defect analysis. They allow thorough characterization of stack composition, strain engineering of the quantum well, background doping levels, and defectivity. Multiple electrical techniques have been used to characterize electron mobility, gate-oxide interface traps, and background doping levels. The images below illustrate the deposition capabilities and stack characterization... Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285838_MHdil44p5p.jpg Caption 1: Figure 1. (a) Reciprocal space mapping data for the SiGe30 buffer showing that it is fully relaxed and (b) TEM EDX map showing minimal diffusion of he Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img2_285838_MHdil44p5p.jpg Caption 2: Figure 2. SIMS depth profile showing Boron and Phosphorous concentrations at or below the detection limits of 1e14 atoms/cm3 and 1e15 atoms/cm3 respec 5 - Poster session Poster presentation 063 Spectroscopy of silicon double quantum dots by dual-port gate-based reflectometry AC Corna1, AC Crippa2, DK Kotekar-Patil1, MR Maurand1, SD De Franceschi1, MS Sanquer1, SB Barraud1, RL Lavieville1, AO Orlov3, XJ Jehl1 1CEA Grenoble, GRENOBLE, France 2Università Milano-Bicocca, Laboratorio MDM, MILANO, Italy 3EE Dept, University of Notre Dame, NOTRE DAME, INDIANA, United States of America Readout of Spin QuBits state usually involves external charge detectors like SET or QPC [Nature 430, 431-435 (2004)]. Recently gate-coupled reflectometry has acquired relevance as a charge-transfer detection tool[PRL 110, 046805 (2013)]. In this scheme charge tunnel events are dispersively detected as phase shifts of reflected signal from a LC resonator. Such resonator is coupled to one gate of the system, which is then used for the electrostatic control and the readout. Its sensitivity can compete with well-established charge sensing techniques [Nat. Commun. 6, 6084 (2015)] while being very compact. Thanks to its compactness, gate-based reflectometry can also be used to probe internal charge transitions, compared to transport measurements which can study only all the tunnel events. The system under investigation is made by two coupled silicon quantum dots, which are controlled by two gates. In this work we used two independent reflectometry lines to study all charge transitions. Each gate has been connected to an inductor to create an LC resonator with the parasitic capacitance. Inductors values are different (270nH and 390nH) in order to get different resonant frequencies (420MHz and 335MHz). We operated our sample in a conductive regime, in order to compare the conductance and reflectometry responses. The stability diagram of current (fig a) shows a couple of conduction triangles, signature of biased double dot system. By looking at the reflectometry signal (fig b) we can separate individual transitions. Measurements of phase shifts for channel 1 (green and violetcolormap) and channel 2 (blue and red colormap) have been superimposed for clarity. Here gate 1 is mostly sensitive to dot1-lead1 transitions, while gate 2 is mostly sensitive to dot2-lead2 and inter-dot transitions. By reversing the bias (fig c) we can see that a portion of the triangle is suppressed and only a faint line is visible. We attribute this effect to Spin Blockade [In preparation]. The faint line is attributed to hyperfine-mediated spin-flip S(0,2) - T(1,1) transition. It can be suppressed with magnetic field (fig d), providing an additional signature of Spin Blockade. We acknowledge the EU through the SiSPIN and SIAM projects.

Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286058_db45PhslHf.png I - Session I: Single donors and acceptors Oral presentation 010 A charge-insensitive single-atom spin-orbit qubit in silicon D. Culcer, J. dr. Salfi, M. Tong, J. A. dr. Mol, S. Rogge University of New South Wales, SYDNEY, Australia High fidelity entanglement of an on-chip array of spin qubits poses many challenges. Spin-orbit coupling (SOC) can ease some of these challenges by enabling long-ranged entanglement via electric dipole-dipole interactions, microwave photons, or phonons. However, SOC exposes conventional spin qubits to decoherence from electrical noise. Here we propose an acceptor-based spin-orbit qubit in silicon offering long-range entanglement at a sweet spot where the qubit is protected from electrical noise. The qubit relies on quadrupolar spin-orbit coupling from the interface and gate potential. As required for surface codes, >10^5 electrically mediated single-qubit and 10^4 dipole-dipole mediated two-qubit gates are possible in the predicted spin lifetime. Moreover, circuit quantum electrodynamics with single spins is feasible, including dispersive readout, cavity-mediated entanglement, and spin-photon entanglement. An industrially relevant silicon-based platform is employed [1,2]. 1. J. Salfi, J. A. Mol, D. Culcer and S. Rogge, arXiv:1508.04259. 2. J. Salfi, M. Tong, S. Rogge and D. Culcer, to appear in Nanotechnology Special Issue on Quantum Information Processing (2016). 5 - Poster session Poster presentation 093 Non-destructive subsurface profiling of laterally patterned 2D phosphorus dopant delta-layers in silicon NJ Curson1, G dr Gramse2, A mr Koelker1, T dr Lim1, E mr Brinciotti3, HS dr Solanki1, TJZ dr Stock1, SR dr Schofield1, G prof. Aeppli1, F dr Kienberger3 1London Centre for Nanotechnology, UCL, LONDON, United Kingdom 2Johannes Kepler University, LINZ, Austria 3Keysight Technologies Austria GmbH, LINZ, Austria In silicon, regions of laterally patterned buried dopant atoms, of dimensions from the nano to atomic scale, will form crucial components of next generation integrated circuits and quantum information processing devices. We use scanning microwave microscopy (SMM) to image patterned 2D phosphorus (P) structures, buried ~15 nm below the silicon surface, with lateral dimensions varying from a few microns to tens of nanometers. The buried structures are fabricated by using a hydrogen resist strategy where the dopants are positioned using a hydrogen resist layer patterned using a scanning tunneling microscope (STM), and encapsulated with epitaxially grown silicon. The SMM technique is completely non-invasive and highly sensitive to the electrical properties of the 2D P structures, with their sheet resistance determined to be in the range of a few kW/sq. By combining SMM with appropriate calibration algorithms and finite element modelling we can quantify the depth of the buried dopant structures (~15 nm) solely using the SMM technique, as confirmed by secondary ion mass spectrometry (SIMS) calibration measurements. At this depth we obtain a lateral imaging resolution of ~70 nm. This demonstration of the ability to determine the depth and electrical characteristics of single atom thick P nanostructures below a silicon surface leads the way towards 3D imaging of nanoscale electrical devices. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_296336_P6RSJLmeZK.png

5 - Poster session Poster presentation 069 The donor bound exciton of phosphorus in silicon inside a nanoscale FET GG De Boo1, C. Yin2, S Freer2, A Laucht2, A Morello2, S Rogge2 1UNSW Australia, SYDNEY, Australia 2CQC2T, University of New South Wales, SYDNEY, Australia The initialization and read-out of the electronic spin states of phosphorous dopants in silicon form the basis of several quantum computing proposals. Fully electronic read-out schemes employ a spin to charge conversion scheme that relies on the contrast between the energetic splitting of two electronic spin states and the energy of electrons in a nearby reservoir. For high fidelity read-out the energy splitting needs to be large, the temperature low and the coupling to the reservoir adequate. An alternative spin to charge conversion for donor spins in silicon is to use the optical transition that creates the donor bound exciton (D0X) [1]. The narrow homogeneous line-width of the optical transitions allows for discrimination between different electronic and nuclear spin states with high fidelity, giving access to the long lived nuclear spin states of phosphorous donors [2]. The D0X state has a large Bohr radius and a small binding energy which cause it to be very sensitive to electric fields and strain, making the use inside a nanoscale device challenging [3]. In this work we explore the possibilities of using the D0X transition to read out electronic and nuclear spin states of individual phosphorus dopants inside a nanoscale field effect transistor (FET). Using charge sensing with Coulomb blockade [4] we perform measurements of excitonic absorption inside a nanoscale FET with phosphorus dopants in the channel. We investigate the effect of electric field on the excitonic absorption by varying the gate potentials. I - Session I: Single donors and acceptors Oral presentation 085 Optimization of a 31P-28Si single-electron-spin qubit using Gate Set Tomography J.P. Dehollain1, J.T. Muhonen2, R. Blume-Kohout3, K.M. Rudinger3, J.K. Gamble3, E. Nielsen3, A. Laucht4, S. Simmons5, R. Kalra4, A. Morello4 1QuTech & Kavli Institute of Nanoscience, TU Delft, DELFT, The Netherlands 2FOM Institute AMOLF, AMSTERDAM, The Netherlands 3Sandia National Laboratories, ALBUQUERQUE, United States of America 4University of New South Wales, SYDNEY, Australia 5Simon Fraser University, BURNABY, Canada State of the art qubit systems are reaching the gate fidelities required for scalable quantum computation architectures. The improvement of high-fidelity qubits can be difficult due to practical accuracy limitations of characterization and benchmarking protocols, and there is a growing need for protocols with can efficiently characterize qubit systems. Gate Set Tomography (GST) is one such protocol designed to give detailed characterization of as-built qubits. We implement GST on a high-fidelity electron-spin qubit confined by a single 31P atom in 28Si. The results reveal systematic errors that were previously hidden by randomized benchmarking, which we correct by improving our pulse-length calibration protocol. After implementing this modification, we measure a new benchmark average gate fidelity of 99.942(8)%, an improvement on the previous value of 99.90(2)%. Furthermore, GST reveals high levels of non-Markovian noise in the system, which would present issues were the qubit to be used in a fault-tolerant scheme. This is a critical issue which needs to be addressed in the subsequent optimizations of our qubit. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286373_oHf4tjenvD.png Caption 1: SEM image and schematic of qubit device, and GST model of qubit

5 - Poster session Poster presentation 042 Trade-offs in engineering a scalable cryogenic CMOS controller for solid-state qubits J.P.G. van Dijk, E. Kawakami, R.N. Schouten, L.M.K. Vandersypen, E. Charbon, F. Sebastiano Delft University of Technology, DELFT, The Netherlands Over the past few years, significant effort has been put in the implementation of quantum bits (qubits) in various technologies, leading to solid-state quantum processors of up to 9 qubits. For proper operation, these qubits are read out and controlled by a classical electronic controller, which is currently implemented by bench-top equipment at room temperature. However, when scaling up the number of qubits to the thousands required for a practical quantum computing application, it would be unpractical to simply multiply the wiring resources between cryogenic quantum processor and room-temperature instrumentation, thus making this approach unsustainable. Proposals have been made to integrate the required electronics for classical controllers in complementary metal-oxide semiconductor (CMOS) technology at an intermediate temperature. A cryogenic CMOS controller would not achieve the same specifications as currently used bench-top equipment, due to the limited cooling power available at the intermediate temperature. It is however not yet clear which is the minimum performance required for such electronics to achieve a certain gate fidelity and coherence time. To address this issue, this work aims at deriving the minimum specifications required for the electrical control of solid-state qubits, as a basis to engineer the qubit electronic controller. While such an analysis is applicable to any qubit technology, we focus on single-electron spin-qubits in an electrostatically defined quantum dot. These qubits promise large-scale integration, allow a purely electrical control, and have long coherence times in isotopic purified silicon. We derive the impact of non-idealities in the signals sent to the quantum processor, such as limited resolution and accuracy in amplitude and time, and non-idealities in the readout electronics, such as electronic noise. As a result, several bottlenecks are identified in the implementation of cryogenic CMOS controllers due to technology limitations and finite power budget. Finally, the analysis reveals how the limited power can be optimally allocated across various control and read-out circuits, given a certain performance budget for the electronics, thus paving the way to the implementation of a cryogenic CMOS controller for the quantum computers of the future. 5 - Poster session Oral presentation 018 Large-scale quantum computation with silicon quantum dot qubits H.G.J. Eenink1, M. Veldhorst2, C.H. Yang3, A.S. Dzurak3 1University of Twente, ENSCHEDE, The Netherlands 2Qutech, DELFT, The Netherlands 3University of New South Wales, SYDNEY, Australia Recent advances in quantum error correction (QEC) codes for fault-tolerant quantum computing and physical realizations of high-fidelity qubits in a broad range of platforms provide encouraging prospects for the construction of a quantum computer based on thousands of interacting qubits. This has motivated the development of classical hardware for qubit control and readout, now emerging as an entirely new field. However, the classical-quantum interface itself has been explored remarkably little. Here we show a design for an all-silicon quantum computer based on CMOS technology, capable of producing billions of transistors on a single chip. We show how a classical transistor control circuit can be used to operate a dense and scalable two-dimensional qubit system. The qubits, which are defined by the spin states of a single electron confined in a quantum dot, are coupled via the exchange interaction and controlled using an ESR cavity, and are measured via gate-based dispersive readout. A key advantage of this circuit design is the possibility of parallel qubit control, allowing many qubits to be addressed within the qubit coherence time using a limited number of control lines. This system, based purely on available technology and existing components, can be used for surface code operations, a promising method for quantum error correction. While only the construction of a dense 2-D array of silicon quantum dot qubits [1,2] is elaborated, the approach is quite general, thus is also suitable for other qubit implementations. [1] M. Veldhorst et al., “An addressable quantum dot qubit with fault-tolerant control fidelity”, Nature Nanotechnology 9, 981 (2014). [2] M. Veldhorst et al., “A two-qubit logic gate in silicon”, Nature 526, 410 (2015).

V - Session V: Quantum dot qubits Oral presentation 073 Valley dependent electron spin resonance in a silicon quantum dot with integrated micro-magnets RUF Ferdous1, EK Kawakami2, PS Scarlino2, MN Nowak2, GK Klimeck1, MF Friesen3, SNC Coppersmith3, MAE Eriksson3, LMKV Vandersypen2, RR Rahman1 1Purdue University, WEST LAFAYETTE, United States of America 2QuTech, Delft University of Technology, Kavli Institute of Nanoscience, DELFT, The Netherlands 3University of Wisconsin-Madison, MADISON, United States of America Electron spins hosted in silicon quantum dots (QD) are attractive building blocks for a quantum computer because of their long coherence times arising from a small spin-orbit coupling (SOC) and a relatively spin-free environment. However electrical manipulation of electron spins is key towards scalable qubit architecture. Integrating micro-magnets into a QD device creates a magnetic field gradient at the dot, which enables electric field induced spin resonance (ESR) by coupling the spin and charge degrees of freedom. Besides spin and charge, Si QDs also have valley degree of freedom in their electronic structure. Though bulk Si conduction band has six degenerate valleys, a silicon quantum dot has two low energy valleys (v+, v-) with a valley splitting separating them. In recent experiments, a valley dependence of the ESR frequency (fv±) was observed with [1] and without [2] the presence of a magnetic field gradient. This exhibits that, though small, the spin-orbit coupling (SOC) in a Si QD has a valley dependence, which can play a crucial role in determining the ESR frequency. In this regard, it is critical for proper qubit operation to understand both the contribution from SOC and magnetic field gradient to the valley dependent ESR. To investigate both these effects and their interplay, we experimentally measure the dependence of the ESR frequencies on the direction of the magnetic field for the valleys (fv±) and their difference (fv+ - fv-), in a Si quantum dot subjected to inhomogeneous magnetic fields. We also observe the B-field dependence of fv± and fv- - fv+ along [110] and [1-10] crystal orientations. With the help of atomistic tight-binding and analytic effective-mass calculation, we explain the experimental measurement and differentiate between the contribution from both SOC and gradient B-field. Our study shows that, SOC introduces 180° periodicity in fv- - fv+, with respect to the direction of the external magnetic field. The presence of gradient field also adds to this anisotropy. But the gradient B-field introduces negligible B-field dependence in the ESR frequencies and their difference. So the experimentally observed B-dependence is solely due to the intrinsic spin-orbit coupling. The atomic scale interface disorder also strongly affects fv± by modulating both the effects. The experimental and theoretical study together provides us with a better understanding of electron spin resonance in a Si quantum dot device. 1. Kawakami et al., Nature Nanotechnology 9, 666-670 (2014). 2. M. Veldhorst et al. PRB 92, 201401(R) 5 - Poster session Poster presentation 057 Charge qubit states in quantum dots : effect of doping on operations and coherence T Ferrus1, T-Y Yang2, Y Yamaoka3, T Kambara3, S Oda3, T Kodera3, D A Williams1 1Hitachi Europe Ltd, CAMBRIDGE, United Kingdom 2Hitachi Europe ltd, CAMBRIDGE, United Kingdom 3Tokyo Institute of Technology, TOKYO, Japan Quantum dot architectures have undeniably regained interest for quantum information despite enormous progress in the realization and the control of both electron and nuclear spin donor-based qubits. However, the need for complex multilayer gate arrangement is still a major difficulty in manufacturing a large ensemble of qubits and currently, most of unitary operations are performed by sending voltage or radiofrequency pulses via metallic gates in close proximity of the device. The use of high concentration dopants in silicon as well as constrictions provides an alternative way to define metallic-like quantum dots without patterning top-gates and allows reducing the number of connections. Our current design incorporates a detector made of a single electron tunnelling device capacitively coupled to an electrically isolated double quantum dot that carries the charge qubit states. In these structures, the uniformity of

dopant concentration is altered near the constrictions (at the detector or the isolated double dot), electron screening is affected and weakly bound states are formed. This surprisingly provides an elegant way of manipulating electrons across a tunnel barrier at GHz frequencies by inducing Spatial Rabi Oscillations using an off-chip microwave antenna. We have recently demonstrated this property and its control in a single quantum dot and applied it to manipulate the qubit states in our isolated double quantum dot. This challenging technique allows extending coherence time much further than theoretically predicted by making use of the electron-electron interaction and potentially reduce scalability problems in the control of qubits to simply microwave multiplexing. Part of this work has been supported by the Project for Developing Innovation Systems of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan 5 - Poster session Poster presentation 072 Charge Qubits Operations in a Double Quantum Dot T Ferrus1, J Mosakowski2, E Owen2, D A Williams3, M Dean2, C H W Barnes2 1Hitachi Europe Ltd, CAMBRIDGE, United Kingdom 2University of Cambridge, CAMBRIDGE, United Kingdom 3Hitachi Cambridge Laboratory, CAMBRIDGE, United Kingdom By looking at the overlap between various qubit bases of a model double quantum dot (DQD) potential, we show that the maximally localised qubit states typically used in DQD systems are inadequate for realizing quantum operations. Instead, we demonstrate that a basis defined in terms of linear superpositions of the bonding and anti-bonding states in the absence of external bias is optimal for qubit initialisation, manipulation and readout. This basis maximises the overlap with qubit states for any detuning, while still being a good approximation to the 2-state model. We also solve the single particle time-dependent Schrodinger equation using a GPU accelerated simulation code to determine the dynamics of this optimal system. As the logical qubit is not the ground state of the system, we demonstrate how to initialise it using a particular sequence of gate pulses, taking into account the expected finite rise times originating from intrinsic instruments or experimental limitations. Under the same conditions, we also show that arbitrary single qubit operations on the Bloch sphere can be achieved if a spin-echo type of pulsing is used. Finally, we link the qubit superposition strength coefficients to the probability of detecting the electron in one of the quantum dots, a parameter that is accessible experimentally in transport measurements. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286092_kPwjjETSYU.jpg Caption 1: Fig. 1. Qubit oscillation amplitude (left) as a function of detunings for a spin-echo pulse type (right). VII - Session VII: Ensemble donors and acceptors Oral presentation 049 Nuclear spin coherence of ionized arsenic donors DPF Franke1, MPDP Pflüger1, PAM Mortemousque2, KMI Itoh2, MSB Brandt1 1Walter Schottky Institut, TU München, GARCHING, Germany 2Keio University, YOKOHAMA, Japan The nuclear spins of ionized donors in silicon are among the most robust quantum systems measured so far, in particular in isotopically purified 28Si [1]. While, most commonly, phosphorus donors are studied as possible qubits, there are several advantages in considering heavier group V donors with higher nuclear spins. Because of the larger Hilbert space, these can provide a higher information density and reduce the number of donors which are needed for a given quantum information process. It has also been shown that for quantum systems with more than two dimensions, the number of necessary operations for the implementation of quantum gates can be reduced drastically. Also in these systems, superpositions of spin states or coherences can be created and are classified by the difference in their nuclear spin quantum number, referred to as the coherence order. In arsenic, which has a nuclear

spin of 3/2, coherences of first, second and third order are therefore possible. The life times of these different coherences can vary significantly because of different coupling strengths to disruptive influences. In particular, the quadrupole interaction with electric field gradients only influences some of the coherences and under certain circumstances is the dominant decoherence process. We present electrically detected electron nuclear double resonance measurements on ionized and neutral arsenic donors and review the quadrupolar effects observed when stress is applied [2,3]. The corresponding shifts to the resonance frequencies facilitate the selective addressing of nuclear spin transitions and in combination with suitable pulse sequences allow for a detailed study of the different nuclear spin coherences. We show coherence time measurements for single, double and triple quantum coherences of ionized donors and discuss the observed decoherence mechanisms. We further apply dynamical decoupling sequences to achieve longer memory times and can give additional information about the time dependence of the decoherence processes involved. [1] Saeedi et al., Science 342, 830 (2013) [2] Franke et al., Phys. Rev. Lett. 115, 057601 (2015) [3] Franke et al., arXiv:1603.01513 (2016) 5 - Poster session Poster presentation 097 Coherent spin transfer through a quantum dot array T Fujita1, T. A. Baart1, C. Reichl2, W. Wegscheider2, L.M.K. Vandersypen1 1TUDelft, DELFT, The Netherlands 2ETH Zurich, ZURICH, Switzerland Distribution of quantum particles across a quantum processor is considered to widen the application of coherent states. This advancement has attracted broad interest in quantum optics and is now considered for semiconductor quantum dot arrays [1-3]. The largest obstacle to quantum computation with solid state devices is the strong interaction with the noisy environment, raising the question to what extent spin coherence is preserved during the transfer. Here we study the shuttling of single electron spins across a one-dimensional quadruple dot array, electrostatically defined in a GaAs 2DEG. Single electrons are passed on from one dot to the next using a sequence of gate voltage pulses. Different from the earlier demonstration of classical spin transfer in a single-spin CCD in a triple dot [4], the inter-dot tunnel couplings are tuned to be above the bandwidth of the shuttling pulses to allow electron shuttling with minimal time jitter. To probe spin coherence, the sequence starts with a two-electron spin singlet state in the leftmost dot of the array. One of the two electrons is next shuttled to the right across successive dots, and is after a short waiting time shuttled back to the leftmost dot where the spin phase is probed using Pauli-spin blockade. In this way we can test shuttling of a superposition state that can be read out without requiring further spin manipulation. As a function of the waiting time before shuttling back, we observe the coherent precession of the two-spin singlet state into the m=0 spin triplet state and back, demonstrating that spin coherence is preserved while shuttling the electron across the quadruple dot. The precession rate depends on the difference in g-factors between the leftmost dot and the dot where the second electron resides during the waiting time. Further investigation of coherent shuttling may lead to the observation of long-range entanglement or environmental effects, for example motional narrowing of nuclear spin fluctuations, that may extend the spin dephasing time in quantum dots. [1] J. Taylor et al., Nature Phys. 1, 177-183 (2005). [2] S. Hermelin et al., Nature 477, 435-438 (2011). [3] R. P. G. McNeil et al., Nature 477, 439-442 (2011). [4] T. A. Baart et al., Nature Nano. 11, 330-334 (2016). 5 - Poster session Poster presentation 083 Designing a flying qubit at a silicon interface K Gamble1, NTJ Jacobson1, ADB Baczewski1, LNM Maurer2, MSC Carroll1 1Sandia National Laboratories, ALBUQUERQUE, United States of America 2University of Wisconsin-Madison, MADISON, United States of America

Spins in semiconductor systems exhibit excellent coherence and operational properties, making them ideal candidates for qubits. However, the very features that lead to these appealing properties make semiconductor qubits difficult to couple over large distances. A variety of solutions have been proposed, including spin buses [1], CTAP [2], cavity coupling [3], direct exchange [4], and capacitive coupling [5]. Here, we revisit an old scheme proposed for GaAs quantum dots: a bucket-brigade CCD-like scheme to shuttle a spin adiabatically across long distances [6]. In order to achieve this in silicon, we need to ensure that the energy gap between the ground and first excited states is large, which presents a challenge given silicon’s small effective mass and conduction band valleys. To assess the feasibility of this scheme, we perform multi-valley effective mass simulations coupled to realistic electrostatic calculations. We simulate the dynamics of electron transport in the presence of both charge traps and interface roughness, optimizing the geometric parameters of the device design (e.g., oxide thickness and gate pitch) to maximize transport fidelity. These results give simple guidelines for developing high-fidelity transport of spins in silicon, representing a path toward plausible flying qubits. The authors gratefully acknowledge support from the Sandia National Laboratories Truman Fellowship Program, which is funded by the Laboratory Directed Research and Development (LDRD) Program. Sandia is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy’s National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. [1] M. Friesen, et al. Phys. Rev. Lett. 98, 230503, (2007). [2] A. D. Greentree, et al. Phys. Rev. B 70, 235317 (2004). [3] Y.-Y. Liu, et al. Phys. Rev. Lett. 113, 036801, (2014). [4] M. Veldhorst, et al. Nature 526, 410-414 (2015). 5 - Poster session Poster presentation 012 Thermalization of Photons with a Driven Solid-State Qubit MJG Gullans1, JS Stehlik2, YL Liu2, CE Eichler2, JRP Petta2, JMT Taylor2 1National Institute of Standards and Technology, GAITHERSBURG, United States of America 2Princeton University, PRINCETON, United States of America A strongly driven quantum system coupled to a thermalizing bath generically evolves into a highly non-thermal state as the external drive competes with the equilibrating force of the bath. We demonstrate a notable exception to this picture for a microwave resonator interacting with a periodically driven charge qubit in a double quantum dot (DQD). In the limit of strong driving and long times, we show that the resonator field can be driven into a thermal state with a chemical potential given by a harmonic of the drive frequency. Such tunable chemical potentials are achievable with current devices and would have broad utility for quantum simulation. As an example, we show how several DQDs embedded in an array of microwave resonators can induce a phase transition to a Bose-Einstein condensate of light. More generally, these results demonstrate the utility of solid-state qubits for studying the thermodynamics of driven quantum systems. II - Session II: Single donors and acceptors Oral presentation 002 Coherent control of spin interaction between a quantum dot and a donor in silicon P. Harvey-Collard1, N. Jacobson1, M. Rudolph1, J. Dominguez1, G.A. Ten Eyck1, J.R. Wendt1, T. Pluym1, J.K. Gamble1, M.P. Lilly1, M. Pioro-Ladrière2, M.S. Carroll1 1Sandia National Laboratories, ALBUQUERQUE, United States of America 2Université de Sherbrooke, SHERBROOKE, Canada Silicon chips hosting a single donor can be used to store and manipulate one bit of quantum information. In particular, donor spins in silicon exhibit extraordinarily long quantum coherence lifetimes. However, a central challenge for

realizing quantum logic operations is to couple donors to one another in a controllable way. To achieve this, several proposals rely on using nearby quantum dots to mediate an interaction. In this talk, I will demonstrate the coherent coupling of electron spins between a single 31P donor and an enriched 28Si metal-oxide-semiconductor few-electron quantum dot. I show that the electron-nuclear spin interaction on the donor can drive coherent rotations between singlet and triplet electron spin states of the quantum dot-donor system. Moreover, the exchange interaction between the QD and donor electrons can be tuned electrically. The combination of single-nucleus-driven rotations and voltage-tunable exchange provides every key element for future all-electrical control of spin qubits, while requiring only a single QD and no additional magnetic field gradients. More fundamentally, this work is an important step towards realizing a donor-based quantum computer without atomic precision fabrication, as originally envisioned in the Kane seminal proposal. Preprint: arXiv:1512.01606. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000. 5 - Poster session Poster presentation 033 Dispersive singlet-triplet readout of the acceptor spin state J van der Heijden1, T. Kobayashi1, M.G. House1, J. Salfi1, S. Barraud2, R. Lavieville2, M.Y. Simmons1, S. Rogge1 1University of New South Wales / CQC2T, SYDNEY, Australia 2University of Grenoble-Alpes and CEA, LETI, GRENOBLE, France Dopant atom based spin qubits in silicon use their intrinsic confinement potential, removing the necessity for confinement gates. However, in the present measurement schemes the elements needed for initialization, manipulation and readout of these spin qubits occupy a large amount of space, which makes scaling up a difficult task. Using acceptor atoms instead of donor atoms, could alleviate this obstacle. The strong spin-orbit interaction between heavy and light hole states enables electrical manipulation of a hole qubit, which removes the need for an inductive ESR line. For an acceptor this spin-orbit interaction can lead to a dipole coupling between the qubit states exceeding 10 Debye [1] because, in contrast to hole quantum dots, the heavy-light hole splitting is much smaller than the orbital level spacing and can be controlled by strain, electric and magnetic fields and the proximity to an interface. Recent experiments have shown that the regime of small heavy-light hole splitting is accessible in silicon nanostructures [2]. A further reduction of the number of gates can be achieved by using the RF gate reflectometry technique, which uses a single gate for dispersive readout and has been successfully demonstrated for donor atoms [3]. Here we show the initialization and readout of a boron atom located in the channel of a silicon tri-gate transistor, fabricated using standard CMOS technology. The singlet-triplet readout is performed by a single gate, using RF reflectometry. The source, drain and backgate are used for further characterization, using complementary transport and gate reflectometry measurements. The singlet-triplet readout is performed where the first hole state of one acceptor is in resonance with the second hole state of another acceptor. The tunnel coupling between the acceptors, measured using a CW excitation between the bonding and anti-bonding singlet states, is 18 μeV. The magnetic field dependence of the inter-acceptor tunneling signal shows hole spin blockade. A singlet-triplet relaxation measurement is performed and T1 is measured to go up to 800 ns. Furthermore, a relaxation hotspot appears when light hole character is mixed into the singlet state, confirmed by excited state spectroscopy. The fast charge relaxation induced by the mixing of heavy and light holes demonstrates the importance of controlling the heavy-light hole splitting to obtain long-lived acceptor spin qubits. [1] J. Salfi et al., arXiv:1508.04259v2. [2] J. van der Heijden et al., Nano Lett., 2014, 14(3). [3] M. G. House et al., Nature Comms., 6, 8848 (2015). 5 - Poster session Poster presentation 100 Quantum simulation of the Mott insulator transition using a semiconductor quantum dot array

T Hensgens1, T Fujita1, L Janssen1, T. A. Baart1, C Reichl2, W Wegscheider2, L. M. K. Vandersypen1 1TU Delft, DELFT, The Netherlands 2ETH Zurich, ZURICH, Switzerland Quantum dot arrays in semiconductors constitute a promising platform for studying the physics of Mott insulators. Not only do tunnel-coupled dots readily adhere to the fermionic Mott-Hubbard model in the elusive regime of low temperature and strong interactions where many-body effects dominate, but one can also directly draw on the extensive toolbox that has been developed for using quantum dots as spin qubits. Here we show unprecedented control of detuning and tunnel coupling for a GaAs laterally defined triple dot array. By keeping the dot energy levels degenerate whilst setting filling and sweeping the ratio of tunneling to interaction energy over more than two orders of magnitude, and measuring all relevant Hamiltonian parameters, we realize a localization transition suggestive of the Stafford-Das Sarma proposal for collective Coulomb blockade and reminiscent of the Mott metal-to-insulator transition. III - Session III: Quantum processor architectures Oral presentation 029 An Architecture For Large-Scale Quantum Computation in Silicon C. Hill1, E Peretz2, J Hille2, G House2, M Fuechsle2, S Rogge2, M.Y. Simmons2, L.C.L. Hollenberg1 1University of Melbourne, MELBOURNE, Australia 2University of New South Wales, SYDNEY, Australia The development of viable architectures which allow the scaling-up to a quantum processors is critical to the implementation of a working quantum computer. This requires the demonstration of qubits and quantum gates (i.e. the DiVincenzo criteria) and, in particular, spatial and temporal considerations of scale-up to be addressed. The high error threshold of the topological surface-code not only requires the arrangement of qubits in a two-dimensional nearest-neighbour array, but it also calls for the control of qubits synchronously and in parallel for stabiliser measurements. The conventional approach assumes independent control for each qubit and their interactions, however, this assumption may lead to significant control complexity bottlenecks, particularly if quantum interconnects are employed for interactions. We introduce a new approach to this problem exploiting the properties of donor based spin qubits in silicon for which a high degree of distributed control and multiplexing is in principle possible [1]. The properties of spin qubits and advances in 3D STM fabrication [2], provide a relatively high degree of uniformity allowing for distributed control, enabling new designs of quantum processor architectures from intermediate to full universal systems. In particular we consider a distributed control architecture for the implementation of the surface-code. The architecture (Figures A-C) comprises three levels: a two-dimensional array of donor qubits placed between two vertically separated control layers above and below the donors, which form a mutually perpendicular crisscross gate array. These shared control lines allow for the loading and unloading of single electrons at multiple specific donor sites, thereby activating multiple qubits in parallel across the array for global control. We show required operations for surface-code error correction - i.e. stabilizer measurements - can be carried out in parallel in a finite number of steps using gate controlled activation and global spin control. By simulating gate-controlled qubit activation and the fundamental CNOT gate we show that the quantum operation error falls below the surface code error threshold for realistic experimental conditions, and that CNOT gates can be made faster with further developments in the architecture design. This shared control approach to donor spin qubits has several advantages: complexities of independent qubit control, wavefunction engineering, and quantum interconnects are avoided, and basic elements of fabrication and control are based on demonstrated techniques [2]. The architecture thus introduces a new pathway for large-scale quantum information processing in silicon and potentially other qubit systems where uniformity can be exploited for distributed control. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285986_ekZB48lG29.png Caption 1: A diagram showing the proposed architecture VI - Session VI: Nano-electronic devices

Oral presentation 016 An FPGA-based cryogenic platform for the classical control of Quantum Computers HAR Homulle1, S. Visser1, B. Patra1, G. Ferrari2, E. Prati2, F. Sebastiano1, E. Charbon1 1TU Delft, DELFT, The Netherlands 2Politecnico di Milano, MILAN, Italy Recent advances in solid-state quantum bit (qubit) technology are paving the way to fault-tolerant quantum computing systems. However, scalable solid-state qubit technology is limited by the need to maintain quantum coherence over time in large qubit arrays and the need to couple the quantum system with a classical electronic infrastructure capable of supporting fault-tolerant protocols. In order to address the fault-tolerant control of large numbers of qubits in parallel, we propose a complementary metal-oxide semiconductor (CMOS) infrastructure to support the micro-architectures enabling to read and control qubits. The infrastructure is implemented entirely on a field-programmable gate array (FPGA) fabricated in a standard 28 nm CMOS technology. The FPGA platform, operating from 4K to 300K, can be employed with several kinds of qubits in their proximity with a moderate temperature gradient. It comprises oscillators, multiplexers and demultiplexers, analog-to-digital converters, and generic logic components. No significant limitations are found in operating the FPGAs at 4K and extensive characterization of the platform is reported at a wide range of temperatures. Together with a performance study, the feasibility of complex circuits is demonstrated with the implementation of time-to-digital and analog-to-digital converters verified to work in a deep-cryogenic environment. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285939_bFNEdFmCqi.png Caption 1: Proposed cryogenic control platform implementing the main control componenents inside the FPGA. 5 - Poster session Poster presentation 040 A compact radio frequency charge sensor for single-spin readout in atomic precision silicon devices G House1, I Bartlett2, P Pakkiam2, M Koch2, E Peretz2, S Hile2, T Kobayashi2, J Van der Heijden2, S Rogge2, M.Y. Simmons2 1UNSW Australia, UNSW SYDNEY, Australia 2Centre for Quantum Computation and Communication Technology, UNSW Australia, SYDNEY, Australia One of the challenges for scaling up silicon spin qubit systems going forward is to fit the required elements (qubits, control electrodes, and charge sensors), into the small space demanded so that the qubits can be coupled together by local interactions. This is a particularly pressing challenge for donor-based qubits, in which the spacing required between the donors is set by donor physics, to less than 20 nm for P donors in Si. A conventional single electron transistor charge sensor requires three leads (source, drain, and gate) and occupies much of the available space in existing one-qubit and two-qubit devices. Direct dispersive measurement of double quantum dot can measure singlet-triplet spin states without the need for a charge sensing structure in the device [1], but it cannot be used to perform a single-spin readout measurement [2]. In this work we realize a compromise between the two approaches by demonstrating that a quantum dot with only one lead can serve as a capacitive charge sensor, suitable for single-spin readout, when measured with radio frequency reflectometry. The rf sensor dot is embedded in a π-matching filter network, which helps to bring the high-impedance of the sensor quantum dot closer to matching the 50 ω transmission line it is connected to, enhancing the reflected signal response. We investigate the optimal input power to drive the sensor given its nonlinear admittance. We demonstrate that the sensor can detect charge transitions on a second quantum dot located 42 nm away, with sufficient sensitivity to achieve single-shot readout at bandwidths competitive with single electron transistors. The new charge sensor will enable simpler, more compact devices for single-spin qubits in the future. [1] M. G. House, T. Kobayashi, B. Weber, S. J. Hile, T. F. Watson, J. van der Heijden, S. Rogge, and M. Y. Simmons, Nature Comms., 6, 8848 (2015). [2] J. M. Elzerman, R. Hanson, L. H. Willems van Beveren, B. Witkamp, L. M. K. Vandersypen & L. P. Kouwenhoven, Nature 450, 431 (2004).

5 - Poster session Poster presentation 084 Decoherence of two-qubit logic gate of spin qubits in Si double quantum dot P Huang1, G. W. Bryant2 1National Institute of Standards and Technology, GAITHERSBURG, United States of America 2National Institute of Stantards and Technology, GAITHERSBURG, United States of America The rapid progress in the manipulation and detection of semiconductor spin qubits enables the experimentaldemonstration of high fidelity two qubit gates that are necessary for universal quantum computing. Here, weconsider the decoherence of two electron spin due to charge noise and phonon emission in a Si double quantumdot (DQD). In the large detuning regime, where the two qubit gate is operated, we find that the decoherence isdominated by charge noise induced spin decoherence. The estimated two qubit decoherence rate is comparable tothe experimental measured results. We discuss the impact of the decoherence on the single/two qubit operationsand ways to reduce the gate errors for the addressable semiconductor spin qubit. 5 - Poster session Poster presentation 039 A valley driven spin qubit in silicon WH Huang1, MV Veldhorst1, Neil Zimmerman2, DC Culcer1, ASD Dzurak1 1University of New South Wales, SYDNEY, Australia 2Princeton University, PRINCETON, NJ, United States of America Silicon is an ideal host for semiconductor spin qubits thanks to the absence of piezoelectric electron-phonon coupling and the existence of isotopes with zero nuclear spin. Recent experiments have realized both single-qubit operations with high fidelity[1], and two-qubit logic gates[2], in silicon metal-oxide-semiconductor (SiMOS) devices operated using oscillating magnetic fields and gate-voltage pulses. In contrast with a.c. magnetic fields, the use of a.c. electric fields for qubit control is attractive because they are easier to produce, and they can be better localized. Initial schemes relied on strong spin-orbit coupling or magnetic field gradients to achieve electron-dipole spin resonance, which has been experimentally realized in GaAs, SiGe and carbon nanotubes[3-5]. However, in materials with weak spin-orbit interactions such as silicon, the interplay between spin-orbit coupling, the valley degree of freedom and an atomistic-scale interface step can result in a drastic increase in electric-dipole spin resonance. Here we outline the way this drastic enhancement arises in Si quantum dots, and discuss ways in which it could be used to achieve fast electrical rotation and entanglement of spin qubits. The enhancement is due to the strong coupling between the ground and excited states which occurs when the electron wavefunction overcomes the potential barrier induced by a step at the silicon/silicon-dioxide interface. A single qubit gate time of 500ns is calculated theoretically. [1] M. Veldhorst et al., Nature Nanotech. 9, 981-985 (2014). [2] M. Veldhorst, et al., Nature 526, 410-414 (2015). [3] A. LairdE, et al, Nat Nano 8, 565 (2013) [4] K. C. Nowack et al, Science 318, 1430 (2007). [5] Kawakami et al, Nat Nano 9, 666 (2014) 5 - Poster session Poster presentation 013 Spin-selective charge transport of heavy holes in a Si double dot

J.-T. HUNG1, B. Wang2, A. R. Hamilton1, D. Culcer1 1University of New South Wales, SYDNEY, Australia 2University of Science & Technology of China, HEFEI, China We investigate spin-orbit-induced tunneling for two heavy-holes confined in a silicon double quantum dot in an in-plane magnetic field. The spin-orbit interaction here includes a cubic Rashba coupling and a magnetic-field-dependent coupling originated from the Luttinger Hamiltonian. We present an effective Hamiltonian to describe the spin-dependent tunneling in a spin blockade regime, and estimate the leakage current in terms of the spin-orbit coupling strength and the in-plane field direction. We find that the Rashba coupling, similar to the electron case, generates an effective tunneling field perpendicular to the double-dot axis. The leakage current then has a minimum when the magnetic field is aligned with the Rashba tunneling field. The magnetic-field-dependent spin-orbit coupling, subject to both bulk parameters and the confinement, is expected to increase the leakage current as the field gets larger. V - Session V: Quantum dot qubits Oral presentation 086 Randomized Benchmarking with an Exchange-Only Si/SiGe Qubit T. no titles Hunter HRL Laboratories, MALIBU, CALIFORNIA, United States of America We will describe the characterization of an exchange-only qubit that encodes quantum information using three-electron spins in a lithographically defined, isotopically enhanced Si/SiGe triple quantum-dot device [1, 2]. To characterize the performance of this qubit, we use randomized benchmarking, composing each Clifford out of a short set of bias-voltage pulses that sequentially turn on the exchange interaction between the left-hand or right-hand pair of electrons. Fast single-shot measurement of the outcome of the benchmarking sequences was accomplished using a low-temperature HEMT amplifier [3]. We will show results of randomized benchmarking on this exchange-only qubit, with a discussion of contributions from known error sources including charge and magnetic-gradient noise and pulse imperfections. M. Borselli, et al, “Undoped Accumulation-Mode Si/SiGe Quantum Dots.”Nanotechnology, 26, 375202 (2015). K. Eng, et al, “Isotopically Enhanced Triple-Quantum-Dot Qubits,”Science Advances, 1, 31500214 (2015). Vink, et al, “Cryogenic Amplifier for Fast Real-Time Detection of Single Electron Tunneling,”Applied Physics Letters, 91, 123512 (2007). 5 - Poster session Poster presentation 061 Cryogenic CMOS LNA for scalable RF read-out of spin qubits RMI Incandela, E. Charbon, F. Sebastiano TU Delft, DELFT, The Netherlands Solid-state qubits must be controlled and read out by classical electronic controllers to ensure proper operation. Because of the low number of qubits in existing quantum processors, only a few wires are currently needed between the cryogenic quantum processor and the electronic controller. This allows electronic controllers placed at room temperature and implemented by bench-top equipment. However, when scaling up to the thousands of qubits required for a practical quantum computer application, simply increasing the wiring would become unpractical. As an alternative, the electronic controller can be placed at cryogenic temperature to simplify the wiring. In order to serve future large-scale quantum processors, controllers must be integrated in technologies enabling large-scale integration, thus making complementary metal-oxide semiconductor (CMOS) technology the best candidate. In this work, we present the design of a cryogenic CMOS Low-Noise Amplifier (LNA) for spin-qubits read-out, which represents the initial step towards a fully-integrated cryogenic CMOS controller for solid-state qubits. Spin qubits can be read out by measuring the impedance a Quantum Point Contact (QPC). This can be

accomplished by RF reflectometry, i.e. by applying an RF signal to the QPC and measuring the reflected power, which is a function of the QPC impedance (Fig. 1). Multiple qubits can be simultaneously addressed by using several RF carriers and frequency-selective matching networks connected to the QPCs. Our goal is replacing the currently used discrete components with a cryogenic CMOS alternative, while maintaining the same performance and optimizing the power consumption per qubit (Fig. 2). This imposes a challenging noise requirement , which is addressed in this design by the adoption of a noise-cancelling LNA architecture. Since the power consumption is mainly determined by noise specifications, the circuit bandwidth has been optimized for the maximum number of qubit channels, so as to minimize the power consumption per qubit. Since no cryogenic CMOS model is available in commercial design tools, the standard CMOS model has been modified and tuned to match the device characteristics measured at cryogenic temperature. The proposed LNA has been designed in a commercial 0.16-μm CMOS process. Simulations at 4 K shows 0.6-K noise temperature, 800-MHz bandwidth (200 MHz-1 GHz) and a 50-mW power consumption, thus enabling the allocation of 40 qubits channels at a power consumption of 1.25 mW/qubits. Even with a cooling power of a few watts at 4 K, such energy efficiency will enable reading out thousands of qubits in future quantum computers. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img2_286056_O9AW6k6frw.png Caption 1: RF reflectometry read-out employing the proposed cryogenic CMOS LNA Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img1_286056_O9AW6k6frw.png Caption 2: Example of current setup for RF reflectometry employing discrete components 5 - Poster session Poster presentation 079 A singlet-triplet qubit coupled to the nuclear spin of a single phosphorus donor NTJ Jacobson1, ADB Baczewski1, JKG Gamble1, RPM Muller1, EN Nielsen1, PHC Harvey-Collard2, MSC Carroll1 1Sandia National Laboratories, ALBUQUERQUE, United States of America 2Universite de Sherbrooke, SHERBROOKE, Canada We have recently demonstrated the coherent rotation of the spin degrees of freedom of a few-electron quantum dot driven by contact hyperfine interaction with a single phosphorus donor nuclear spin in isotopically purified silicon [1]. The operation of this device is similar to that of singlet-triplet qubits in GaAs, in that neighboring nuclear spins establish an effective field gradient to drive rotations of the electronic degree of freedom. However, in this donor-dot system the electrons experience the smallest of spin environments: a “bath”of one spin-1/2 nucleus. This allows for the possibility of using the nuclear degree of freedom as a long-lived quantum memory for a singlet-triplet qubit, exploiting the remarkably long coherence times of 31P donors that have been demonstrated in isotopically purified silicon [2,3]. Here, I will detail our physical modeling of this donor-dot system as a heterogeneous pair of coupled two-level systems. In addition, I will describe the donor nuclear spin’s effect on singlet/triplet qubit operation and discuss the prospects for initializing the spin of the donor nucleus through dynamic nuclear polarization. Sandia is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy’s National Nuclear Security Administration under Contract No. DE- AC04-94AL85000. [1] P. Harvey-Collard, et al. arXiv:1512.01606 [2] K. Saeedi, et al. Science 342, 830 (2013) [3] J. Muhonen, et al. Nat. Nano. 9, 986 (2014) 5 - Poster session Poster presentation 015 Exploring Limits of Deterministic Single Ion Implantation for Silicon Quantum Electronics Fabrication

AMJ Jakob, B.C. Johnson, S Gregory, D.N. Jamieson University of Melbourne, MELBOURNE, Australia The remarkable success in addressing and manipulating ion implanted single P-donor spins (“qubits”) in 28Si represents a cornerstone for the realization of ground-breaking quantum-computing and information transport applications [1]. Inspired by these results, scientists recently proposed a multitude of promising architectures such as the shared-controlled surface code [2], long-distance electric dipole spin coupling [3] as well as multi-valley spin qubits and superconducting quantum circuits. They all take advantage of ordered qubit ensembles to exploit the spin-entanglement constituting a fundamental prerequisite to form a fully functional quantum computer. However, the ensemble’s susceptibility to environmental disturbances like inter-qubit spacing fluctuations as well as the necessity of high-fidelity single qubit addressing in tightly integrated array architectures require a donor placement precision of <6 nm as predicted from previous solid state calculations. In our present study we seek to exploit ultimate limits of post-detection single ion implantation for fabricating technologically relevant P-qubit arrays with the necessary placement fidelity. Our combined computational- experimental study addresses fundamental structural and electronic device constraints that substantially determine the donor placement accuracy of this semiconductor industry-compatible top-down manufacturing approach [4]. We employ a novel break-through ultra-low-noise apparatus to detect sub-10 keV P-ions and examine on-chip detectors of different device architecture for deterministic ion implantation. Their detection characteristics are discussed considering device properties like passivation layer thickness as well as fundamental aspects arising from ion-matter interaction at low ion energies. Our present systematic study particularly assesses standard device-processing approaches for passivation layer thickness manipulation that is shown to be crucial for optimum ion-straggling suppression while allowing for the best possible single ion detection efficiency. We finally evaluate these findings within the context of large-scale quantum device fabrication and reliability-optimisation of deterministic single ion implantation for high-fidelity donor placement. [1] J. T. Muhonen et al., “Storing quantum information for 30 seconds in a nanoelectronic device”Nature Nanotech., vol. 9, 2014 [2] C. Hill et al., “A surface code quantum computer in silicon”, Sci. Adv. 1500707. 2015 [3] G. Tosi et al., “Silicon quantum processor with robust long-distance qubit couplings”, arXiv:1509.08538, 2015 [4] J. v. Donkelaar et al., “Single atom devices by ion implantation”, J. Phys.: Condens. Matter, vol. 27, 2015 5 - Poster session Poster presentation 059 Design and cryogenic operation of silicon electron pumps and ring oscillators X Jehl1, P Clapera1, A Valentian2, S Barraud2, L Hutin2, S De Franceschi1, M Sanquer1, M Vinet2 1INAC and Université Grenoble Alpes, GRENOBLE, France 2LETI and Université Grenoble Alpes, GRENOBLE, France We design, fabricate, and operate at cryogenic temperatures electron pumps driven by RF ring oscillators. All elements are fabricated using industry-standard 300mm silicon-on-insulator (SOI) technology (see inset(c)), which involves optical (deep UV) lithography [1]. The electron pump consists of a silicon nanowire channel with two top gates which isolate a single metallic (NiPtSi) Coulomb island (see Fig(a)) and act as fast tunable barriers. Operation and performances comparable to devices featuring e-beam lithography [2] are demonstrated, with a pumping frequency up to 300MHz [3]. Moreover we observe features which indicate that pumping is less sensitive to static charge traps than dc transport measurements. The ring oscillator circuit is designed to generate on-chip RF signal whose frequency can be tuned from tens of kHz up to GHz by means of an external DC voltage (see Fig(b)).This clock output signal is further split into two signals, with a controlled phase shift between themto drive the two gates of the electron pump. The whole circuit, including capacitance dividers and bias resistors, is fully operational down to 1.1K [4]. These results bear relevance for the development of cryogenic CMOS electronics for qubit control. [1] <i>Performance of Omega-Shaped-Gate Silicon Nanowire MOSFET With Diameter Down to 8 nm<, S. Barraud et al, <i>IEEE Electron Device Letters, 33, 1526, (2012). [2] Hybrid Metal-Semiconductor Electron Pump for Quantum Metrology, X. Jehl et al,Phys. Rev. X 3, 021012 (2013). [3] Design and Cryogenic Operation of a Hybrid Quantum-CMOS Circuit, P. Clapera et al,Physical Review Applied 4, 044009 (2015). [4] Design and operation of CMOS-compatible electron pumps fabricated with optical lithography, P. Clapera et al,submitted (2016).

Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286052_ZHqeW3CQke.jpg Caption 1: (a) colorized SEM of a deep-UV electron pump. (b) Output of the ring oscillator versus dc control voltage (c) CMOS chip under test at 300K. 5 - Poster session Poster presentation 074 Supressing Segregation in Highly Doped Silicon Monolayers J.G. Keizer1, S.R. McKibbin1, S Koelling2, P.M. Koenraad2, M.Y. Simmons1 1University of New South Wales, SYDNEY, Australia 2Eindhoven University of Technology, EINDHOVEN, The Netherlands Abrupt dopant profiles and low resistivity are highly sought after qualities in the silicon microelectronics industry and, more recently, in the development of an all epitaxial Si:P based quantum computer. Previously, we have shown that increasing the dopant density by growing multiple layers is ultimately limited the formation of P-P dimers due to the segregation of dopants between multi-layers [1]. To suppress this segregation, and thereby creating more abrupt dopant profiles and higher active carrier densities, we investigated the application of thin room temperature grown silicon layers, so-called locking layers. Atom probe tomography and magneto-transport measurements show these locking layers are effective in suppressing segregation but reduce the active carrier density. However, we find that the careful application of a rapid thermal anneal can restore the active carrier density whilst maintaining an abrupt dopant profile. In this way we were able to achieve a fully activated P dosed layer that is confined within ~1nm and has a 3D dopant density of 2.5-3 atm. %, well beyond what was previously achieved for phosphorus dosed delta-layers. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286102_UbcCzHaIdb.png Caption 1: P-profile (APT) for different locking layer thickness and the active carrier density after the thermal anneal. 5 - Poster session Poster presentation 055 Gate design simulation of open systems JK Klos, PC Cerfontaine, FH Hassler, HB Bluhm, LS Schreiber RWTH Aachen University, AACHEN, Germany The increasing complexity and urge of scalability of gate-defined quantum systems make a prior stimulation mandatory to verify functionality, control and feasibility of the multi-layer gate designs. Most simulations are based on linear approaches using either electro-static superpositions or non-linear approaches such as Thomas-Fermi-approximation aiming at gate-specific cross covariance matrices [1]. Including additional non-linear conditions on the gate design such as tunnel couplings in closed systems e.g. a double quantum dot (QD) are well understood and implemented. More sophisticated dependencies on the gate design such as tunnel coupling to open systems e.g. the electron reservoir are often approximated by the Wentzel-Kramers-Brillouin (WKB) approximation. Here, we demonstrate a new approach using Green’s formalism for calculating the tunnel coupling of an open system. The total Hamiltonian is separated into three subsystems: a QD, an intermediate system capturing the details of the potential landscape of the electron reservoir close to the QD and a shapeless lead system with each system coupled by next-neighbor transition elements. The SET and intermediate subsystem are solved by the SG. Green's formalism allows straight forward application of Markov approximation in the lead subsystem. Due to the coupling of the intermediate and lead subsystem, the Hamiltonian of the total reservoir becomes non-hermitian. Since within Green’s formalism the self-energy corresponds to the influence of a coupled neighboring system, the resulting imaginary self-energy corresponds to an electron tunneling into the reservoir. Following this definition, the tunnel

coupling of an open system equals the imaginary part of the self-energy of the SET system coupled to a non-hermitian reservoir for a sufficiently large intermediate system. Combining algorithms for the calculation of the tunnel coupling of closed and open systems, as well as gate-tuning, we aim at a powerful toolkit suitable for simulations of gate patterns on various heterostructures. We applied the toolkit to a new QD read-out structure design (Fig. 1,2) that consist of accumulation and depletion gates on an undoped SiGe heterostructure [2, 3]. In contrast to common designs, our gate design uses the SET for both read-out and as an electron reservoir due to finite tunnel-coupling to the QD containing the spin qubit. A corresponding read-out scheme has been presented for spin qubits bound to single phosphor donors in Si [4]. [1] A. Frees et al., arXiv:1409.3846(2014) [2] M.G. Borselli et al., IOP, 26, 375202(2015) [3] D. Zajac et al., APL, 106, 223507(2015) [4] A. Morello et al., PRB, 80, 081307(2009) Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286042_XoalDnQGMp.png Caption 1: QD Read-out gate structure. Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img2_286042_XoalDnQGMp.png Caption 2: Corresponding potential landscape for set of voltages tuned by using the toolkit. 5 - Poster session Poster presentation 070 Fabrication and characterization of physically-defined quantum dots in an ultrathin silicon-on-insulator layer TK Kodera1, S. Ihara1, T. Nishino1, S. Hiraoka1, A. Andreev2, D. Williams2, S. Oda1 1Tokyo Institute of Technology, MEGURO-KU, Japan 2Hitachi Cambridge Laboratory, CAMBRIDGE, United Kingdom Recently, silicon quantum dots (Si QDs) have been well studied for implementing quantum information devices. We study physically-defined QDs fabricated on Si-on-insulator (SOI) substrates with some advantages for future integration [1-4]. Physically-defined Si QDs require no gates for creating confinement potentials of the QDs, which is technologically simple owing to reduced number of gates. For fabrication of the physically-defined Si QDs in metal-oxide-semiconductor (MOS) structures, we utilize electron beam lithography, reactive ion etching, and oxidation. Fabrication process of Si MOS technologies can be applied to our Si QD devices. We fabricated and characterized electrostatically-coupled two Si single QDs on ultrathin (~6 nm) SOI [4]. Change in number of electrons in one of the two Si QDs was detected using the other QD as a charge sensor. We obtained comparatively large charging energy (~ 20 meV), which is estimated from regularly-patterned Coulomb diamonds of the Si single QD. We performed three-dimensional calculations of capacitance matrix and transport properties through the QD and found a good quantitative agreement with experiment. This work was financially supported by JSPS KAKENHI (Nos. 26709023, 26630151, and 26249048), and the Project for Developing Innovation Systems of the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. G. Yamahata, T. Kodera, H. O. H. Churchill, K. Uchida, C. M. Marcus, and S. Oda Phys. Rev. B 86, 115322 (2012). K. Horibe, T. Kodera, and S. Oda, Appl. Phys. Lett. 106, 083111 (2015) K. Horibe, T. Kodera, and S. Oda, Appl. Phys. Lett. 106, 053119 (2015) S. Ihara, A. Andreev, D. A. Williams, T. Kodera, and S. Oda, Appl. Phys. Lett. 107, 013102 (2015) 5 - Poster session Poster presentation 058 Towards silicon quantum dots coupled to superconducting devices

AVK Kuhlmann IBM Research-Zurich, RUESCHLIKON, Switzerland Silicon (Si) and in particular isotopically purified 28Si are very attractive hosts for spin-based quantum devices. Recently, spin coherence times approaching seconds have been reported [1-3]. We develop a joint silicon based platform for metal oxide semiconductor (MOS) quantum dot (QD) qubits and superconducting microwave circuits to combine the long spin lifetimes in silicon quantum dots, the know-how from scalable CMOS fabrication with the non-local control/coupling mediated by superconducting cavities [4-6]. In our poster, we discuss the fabrication of both silicon quantum dots as well as superconducting coplanar waveguide resonators (CPWs) and present the first characterization measurements. A double QD design is realized in a CMOS compatible process both in planar and non-planar configurations. The latter requires additional pre-pattering of the Si substrate with narrow fins. The combination of high-resolution e-beam lithography with dry etching allows for a quantum dot pitch of less than 50 nm. To allow for full two-axis spin control we plan to integrate micro magnets into our design [6, 7], which will require optimization of the superconducting structures and materials. In this respect, we will present first results on superconducting coplanar waveguide resonators and the design of the hybrid device. For the CPWs we investigate different superconducting materials in terms of q-factor and process compatibility. 1. A. M. Tyryshkin et al., Nature Mater. 11, 143 (2012) 2. M. Veldhorst et al., Nature 526, 410 (2015) 3. K. Eng et al., Sci. Adv. 1, e1500214 (2015) 4. T. Frey et al., Phys. Rev. Lett. 2012 108, 046807 (2012) 5. G.-W. Deng et al., Nano Lett. 15, 6620 (2015) 6. J. J. Viennot et al., Sci. Rep. 349, 408, (2015) 7. E. Kawakami et al., Nature Nanotech. 9, 666 (2014) 8. Y. Tokura et al., Phys. Rev. Lett. 96, 047202 (2006) 5 - Poster session Poster presentation 011 Spin Qubits in Silicon - Advantages of Dressed States AL Laucht1, R. Kalra1, M.Y. Simmons1, J.P. Dehollain1, J.T. Muhonen1, G. Tosi1, F.A. Mohiyaddin1, S. Freer1, F.E. Hudson1, K.M. Itoh2, D.N. Jamieson3, J.C. McCallum3, A.S. Dzurak1, A. Morello1 1CQC2T, UNSW, SYDNEY, Australia 2Keio University, HIYOSHI, Japan 3CQC2T, University of Melbourne, MELBOURNE, Australia Coherent dressing of a quantum two-level system has been demonstrated on a variety of systems, including atoms [1], self-assembled quantum dots [2], and superconducting quantum bits [3]. Here, we present coherent dressing of a single electron spin bound to a phosphorus donor in silicon. We observe a Mollow triplet [1] in the excitation spectrum (see Fig. 1), perform coherence time measurements on the driven qubit, and demonstrate full two-axis control of the driven qubit in the dressed frame with a number of different control methods. In our work we investigate the properties of a dressed electron spin, and probe its potential for the use as quantum bit in scalable architectures where the two spin-polariton levels constitute the quantum bit. The dressed qubit can then be coherently driven with an oscillating magnetic field, an oscillating electric field, by frequency modulating the driving field, or by electrically modifying its detuning. We measure coherence times of T2ρ*=2.4 ms and T2ρ=9.2 ms, longer than those of the undressed qubit. Furthermore, we demonstrate that the dressed spin can be driven at Rabi frequencies as high as its transition frequency, making it a model system for the breakdown of the rotating wave approximation. This research was funded by the ARC Centre of Excellence for Quantum Computation and Communication Technology (project number CE110001027) and the US Army Research Office (W911NF-13-1-0024). [1] B. R. Mollow. Phys. Rev. 188, 1969 (1969). [2] X. Xu et al. Science 317, 929 (2007). [3] M. Baur et al. Phys. Rev. Lett. 102, 243602 (2009). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285890_5CvTn1TX1I.png Caption 1: Dressing a single electron spin in silicon - Rabi oscillations and Mollow triplet.

V - Session V: Quantum dot qubits Oral presentation 001 Transporting a single-spin qubit through a double quantum dot X Li1, E Barnes2, J Kestner3, S Das Sarma1 1University of Maryland, COLLEGE PARK, United States of America 2Virginia Tech, BLACKSBURG, VA, United States of America 3University of Maryland Baltimore County, BALTIMORE, MD, United States of America Coherent spatial transport or shuttling of a single electron spin through semiconductor nanostructures is an important ingredient in many spintronic and quantum computing applications. In this work we analyze the possible errors in solid-state quantum computation due to leakage in transporting a single-spin qubit through a semiconductor double quantum dot. In particular, we consider three possible sources of leakage errors associated with such transport: finite ramping times, spin-dependent tunneling rates between quantum dots induced by finite spin-orbit couplings, and the presence of multiple valley states. In each case we present quantitative estimates of the leakage errors, and discuss how they can be minimized. Moreover, we show that in order to minimize leakage errors induced by spin-dependent tunnelings, it is necessary to apply pulses to perform certain carefully designed spin rotations. We further develop a formalism that allows one to systematically derive constraints on the pulse shapes and present a few examples to highlight the advantage of such an approach. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285427_FalYzwt090.png Caption 1: Potentials for a double quantum dot Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img2_285427_FalYzwt090.png Caption 2: Rotations of a spin state 5 - Poster session Poster presentation 056 Silicon quantum dots with counted antimony donor implants P Lilly Sandia National Labs, ALBUQUERQUE, United States of America Antimony donor implants next to silicon quantum dots have been detected with integrated solid-state diode detectors with single ion precision. Devices with counted number of donors have been fabricated and low temperature transport measurements have been performed. Charge offsets, indicative of donor ionization and coupling to the quantum dot, have been detected in these devices. The number of offsets corresponds to 10-50% of the number of donors counted. We will report on tunneling time measurements and spin readout measurements on the donor offsets. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. The work was supported by Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000. III - Session III: Quantum processor architectures Oral presentation

019 Surface code architecture for donors and dots in silicon with imprecise and nonuniform qubit couplings W Lovett1, G. Pica1, S. A. Lyon2, R. N. Bhatt2, T. Schenkel3 1University of St Andrews, ST ANDREWS, United Kingdom 2Princeton University, PRINCETON, United States of America 3Lawrence Berkeley National Lab, BERKELEY, United States of America A scaled quantum computer with donor spins in silicon requires a viable semiconductor framework and a strong inherent decoupling of the qubits from their noisy environment. Coupling neighbouring spins via the natural exchange interaction according to current designs requires gate control structures with extremely small length scales. Here, we will present a blueprint for a silicon surface code architecture [1] (Fig. 1) where bismuth donors with with long coherence times at clock transitions [2] are coupled to electrons that can shuttle between adjacent quantum dots. This design enables the precision with which donors must be placed to be relaxed, allows much more space between donors than previous architectures [see e. g. 3], and this extra space makes room for classical control devices. An adiabatic SWAP operation within each donor/dot pair solves the scalability issues intrinsic to exchange-based two-qubit gates [4,5], since it works across a wide range of possible exchange coupling values (Fig. 2). It therefore does not rely on sub-nanometer precision in donor placement and is robust against noise in the control fields.We will show how to use this SWAP together with well established global microwave Rabi pulses and parallel electron shuttling to construct a surface code that needs minimal, feasible local control. Surface code architectures have been shown to have extremely high tolerance to errors [6] and this, together with the ultra long coherence times of silicon donors brings the prospect of silicon quantum processors every closer.[1] Surface code architecture for donors and dots in silicon with imprecise and nonuniform qubit couplings, G. Pica, B. W. Lovett, R. N. Bhatt, T. Schenkel and S. A. Lyon, Phys. Rev. B 93 035306 (2016)[2] Atomic clock transitions in silicon-based spin qubits, G. Wolfowicz, et al., Nat. Nanotechnol. 8 561 (2013).[3] A silicon-based nuclear spin quantum computer, B. E. Kane, Nature 393 133 (1998)[4] Exchange in Silicon-Based Quantum Computer Architecture, B. Koiller, X. Hu and S. Das Sarma, Phys. Rev. Lett. 88 027903 (2001)[5] Exchange coupling between silicon donors: The crucial role of the central cell and mass anisotropy, G. Pica, B. W. Lovett, R. N. Bhatt, and S. A. Lyon, Phys. Rev. B 89 235306 (2014)[6] Surface codes: Towards practical large-scale quantum computation, A. G. Fowler, M. Mariantoni, J. M. Martinis, and A. N. Cleland, Phys. Rev. A 86 032324 (2012)”� Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img2_285949_qkzNcduqzZ.png Caption 1: Despite the range of J couplings caused by imprecise donor positioning d, almost all pairs in the array, i.e. those in green, would undergo SWAP gates Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img1_285949_qkzNcduqzZ.png Caption 2: Schematic diagram of the donor-dot array structure. Data qubit donor electrons are positioned below gate defined dots acting as measurement qubits. 5 - Poster session Poster presentation 094 Designing devices for single donor spin read-out via donor-bound exciton transitions: effects of strain and donor position JM Mansir, PR Mr. Ross, CCL Dr. Lo, JJLM Prof. Morton University College London, LONDON, United Kingdom A neutral donor-bound exciton is a four-body complex generated by below-bandgap optical excitation of a semiconductor doped with donor impurities. Donor-bound exciton transitions present a potential hybrid electrical-optical mechanism for read-out of single donor spins in silicon at temperatures of 4.2 K and magnetic fields below 1 T, significantly relaxing the experimental requirements when compared with other single spin read-out techniques such as spin-dependent tunnelling. We present simulation and experimental data addressing the issues of strain and optimal donor position, which are crucial to consider when designing nanoscale devices for single-donor spin readout via bound-exciton transitions.

IV - Session IV: Quantum dots and nanowires Oral presentation 065 Electrically controlled CMOS hole spin qubit RM Maurand1, DKP Kotekar Patil2, AC Corna2, XJ Jehl2, RL Lavieville3, LH Hutin3, SB Barraud3, MV Vinet3, MS Sanquer2, SF De Franceschi2 1CEA Grenoble, GRENOBLE, France 2CEA-INAC, GRENOBLE, France 3CEA-LETI, GRENOBLE, France One solution towards solid-state quantum computation would be not to scale-up existing quantum bits but rather to ``quantumize`` already integrated bits. Today’s microelectronic technology has brought transistors to ultimate size on the order of ten nanometers. At this scale and at low temperature such transistors behave as a quantum dots in which a single spin can be isolated. Moreover, hole spins in silicon represent an attractive direction since they possibly combine fast qubits with limited hyperfine interaction [1]. Here we demonstrate that a trigate CMOS nanowire transistor [2] can be operated as a hole spin qubit. Devices studied are similar to industrial silicon-on-insulator transistors except that they feature two gates in series and oversized nitride spacers to define a double quantum dot (see Fig.a). Working specifically with PMOS transistors, we show that a microwave frequency signal applied to one gate induces a hole spin resonance [3] detected via Pauli spin blockade. Pulsing the device from spin blockade to Coulomb blockade, we demonstrate coherent manipulation (see Fig.b) with Rabi frequencies as high as 80MHz with an inhomogeneous dephasing time T2*~80ns. Our experiment demonstrates that industry-standard CMOS transistors can be operated as hole spin qubits with an electrical control providing fast rotation and universal single gate control. [1] B. Voisin et al. Nano Lett. 16, 88 (2016). [2] S. Barraud et al. IEEE 33, 1526 (2012). [3] V. S. Pribiag et al. Nat. Nanotechnol. 8, 170 (2013). We acknowledge the EU through the ERC starting grant HybridNano and the SiSPIN and SIAM projects. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286071_hvTg3TJEVI.png Caption 1: a) SEM micrograph of a SOI double gate transistor. b) Rabi chevron pattern 5 - Poster session Poster presentation 091 Scanning Tunneling Lithography Toolset SM Misra1, D. R. Ward1, D. Scrymgeour1, R. J. Simonson1, M. T. Marshall1, J. Koepke1, J. Ballard2, J. Owen2, U. Fuchs2, S. Schmucker2, S. Pryadkin2, J. Randall2, E. Bussmann1, M. S. Carroll1 1Sandia National Laboratories, ALBUQUERQUE, United States of America 2Zyvex Laboratories, DALLAS, United States of America Donor-based qubits require precise donor placement to realize multi-qubit gates due to the rapid fluctuations in donor-donor coupling at the atomic scale. Scanning tunneling microscopy (STM) presents a conceptually attractive fabrication path that enables the atomically precise placement of phosphorus donors in silicon. Because the requisite circuitry to initialize and read out the donors must be well-aligned to them, these are also made using STM. Unfortunately, even commercial STMs are research-grade tools designed for imaging, and the fabrication of devices, necessary for systematic studies of the underlying device physics, is slow. The logical decomposition of a device layout for serial lithography, as done with electron beam lithography (EBL), has not been possible with STM. Here, we detail our efforts to expand the lithographic capability and speed of the STM by adapting three key concepts from EBL. Chief amongst these, we have created a pattern generation tool that translates CAD files into a set of ‘write’ vectors. The separation of what gets written and how it gets written

streamlines the communication and standardization of device patterns, while allowing for operators to efficiently manage the vagaries of STM. Second, we have implemented an automated alignment scheme which gives a fine alignment of a few nm through the entire write field of 6mm. Combined, these low-level capabilities create a process flow that allows for accurate lithography of most of a device with no human intervention, a critical increase in throughput when a typical device area is 10 um2, and scanned probe lithography is slow (~0.001 um2/ sec). Finally, we have developed a technique to use a standard long focus optical microscope to do coarse location of the tip relative to etched chip marks. This technique allows for absolute location of the tip to within 5 um, sufficient to allow the same area to be found again using a 6 um scan. Combined with the appropriate use of fiducial marks, this opens the door to stitching write fields together to make larger area devices. More immediately, it increases yield by allowing for changing a bad tip out for a new one to continue patterning. Remaining issues for research scale device fabrication include resist and tip lifetimes as well as stitching of multiple write windows. 5 - Poster session Poster presentation 024 Bidirectional electron pumping using a silicon quantum dot MM Möttönen1, TT Tanttu1, AR Rossi2, KYT Tan1, AM Mäkinen1, KWC Chan3, ASD Dzurak3 1Aalto University, AALTO, Finland 2Cavendish Laboratory, University of Cambridge, CAMBRIDGE, United Kingdom 3University of New South Wales, SYDNEY, Australia Quantum dots have shown great potential in directly implementing the emerging SI ampere that is based on a fixed value of the electron charge and the standard of time. To this end, single electrons have been pumped with uncertainties of about 0.2 ppm at half-gigahertz frequency [1]. Such high precision and speed seems already satisfactory for fault-tolerant quantum computing based on spins in silicon [2]. Namely, these methods potentially allow in the future to conveniently transport an electron carrying the quantum information to an interaction site and back to its original position without introducing significant error. In this work, we utilize a silicon quantum dot architecture that has previously been used in high-precision electron pumping [3]. By introducing an individual sinusoidal driving voltage to each of the three gates defining the dot, two barrier gates and the plunger gate, we obtain a high level of control over the potential landscape. We show that the third control voltage significantly improves the robustness of the pump and renders it possible to change the pumping direction simply by changing the phase of one drive with respect to the two others [4]. In the future, we attempt to utilize the three-waveform pumping to upgrade our electron counting experiments [5] into error counting, and consequently to implement a self-referenced metrological current source for the emerging quantum ampere. Furthermore, we look forward on the demonstration of a quantum bus for the silicon quantum computer based on the principles of the electron pump. [1] F. Stein et al., Appl. Phys. Lett. 107, 103501 (2015). [2] M. Veldhorst et al., Nature Nanotechnol. 9, 981 (2014). [3] A. Rossi et al., Nano Lett. 14, 3405 (2014). [4] T. Tanttu et al., arXiv:1603.01225 (2016). [5] T. Tanttu et al., New J. Phys. 17, 103030 (2015). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img2_285978_KbfM0AH7iX.jpg Caption 1: Pumped direct current as a function of the plunger dc voltage and rf phase. Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img1_285978_KbfM0AH7iX.jpg Caption 2: Sample and pumping protocol. 5 - Poster session Poster presentation

045 Crossing quantum-classical boundaries with a single nuclear spin V Mourik1, S Asaad1, H Firgau1, C A Holmes2, G J Milburn2, J Mccallum3, A Morello1 1University of New South Wales, SYDNEY, Australia 2University of Queensland, BRISBANE, Australia 3University of Melbourne, MELBOURNE, Australia The exotic features of quantum mechanics such as superposition, entanglement and teleportation, never fail to capture the attention of scientists and public alike. Far less attention is given to the fact that, when looking at a quantum system compared to its classical counterpart, the stark divergence of their dynamics is generic and straightforward. Classical conservative systems usually exhibit rapid dispersion of initial conditions - chaos - while the quantum version of the same systems exhibit quasi-periodicity, localization and tunneling through classically forbidden regions of phase space. How to reconcile this strikingly different behavior has been the topic of much theoretical debate, but little experimental proof, and none whatsoever on a single quantum system observed in real time. Our project aims at achieving the first real-time experimental observation of the quantum dynamics of a single classically chaotic system - a periodically-driven non-linear top. To implement this system, we will utilize the existing infrastructure of the Phosphorus donor qubit, but replace the donor by an Antimony isotope, 123-Sb, which has a nuclear spin of 7/2. Choosing 123-Sb over 31-P leads to both the necessary enlargement of the nuclear spin Hilbert space, from 2 to 8 dimensions, and the necessary incorporation of a non-linearity due to the nuclear quadrupole interaction, which is quadratic in nuclear spin operators. Adding a periodic drive will lead to an exact implementation of the periodically-driven non-linear top. The excellent properties of record long coherence time of the nuclear spin and high fidelity single shot read-out, as observed with 31-P, combined with the properties of the 123-Sb donor, will enable us to study the quantum-classical crossover in the nuclear spin’s dynamics. We will present a detailed outline of our upcoming experiments and their theoretical modeling. Starting from the physical properties of 123-Sb as a donor in Si, we will then present our results on modeling the time evolution of the nuclear spin in the presence of a periodic drive. Finally, we will make the link to the classical dynamics by identifying deviations and correspondence in the quantum case and discuss their actual experimental observation. 5 - Poster session Poster presentation 102 Quantum Simulation of Fermi-Hubbard model using Quantum Dot Array U Mukhopadhyay1, T. Hensgens1, C. Reichl2, W. Wegscheider2, M. Manfra3, L. M. K. Vandersypen1 1TU Delft, DELFT, The Netherlands 2ETH Zurich, ZURICH, Switzerland 3Purdue University, PURDUE, United States of America Quantum simulation has attracted a lot of attention as a means of tackling classically intractable many-body problems through emulation of the underlying model. Here we report our progress on simulating Fermionic Mott-Hubbard physics in a 2-dimensional array of quantum dots, which readily adheres to the same Hamiltonian. Voltages applied to nanofabricated top gate layers on the sample create a periodic potential difference in the 2D electron gas (2DEG), forming a 2D quantum dot array. Using capacitance spectroscopy, the density of states in the 2DEG is measured as a function of Fermi energy. In forming the quantum dot array through varying the periodic potential, metal-insulator transition is expected to take place. Moreover a magnetic field applied perpendicular to the dot plane can provide access to exciting Hofstadter physics. 5 - Poster session Poster presentation 007 Robust quantum dot devices for qubits in isotopically purified 28Si CN Neumann1, TL Leonhardt2, FB Borjans2, FS Schauer1, SS Schwaegerl1, JK Kierig1, AW Wild3, JWA Ager4, EEH

Haller4, NVA Abrosimov5, GA Abstreiter6, KS Sawano7, SL Ludwig8, LS Schreiber2, DB Bougeard1 1Universitaet Regensburg, REGENSBURG, Germany 2RWTH Aachen University, JARA-Institute for Quantum Information, AACHEN, Germany 3Walter Schottky Institut & ZNN, Technische Universitaet Muenchen, GARCHING, Germany 4Lawrence Berkeley National Laboratory, Materials Sciences Division, BERKELEY, United States of America 5Leibniz-Institute for Crystal Growth, BERLIN, Germany 6Technische Universitaet Muenchen, Institute for Advanced Study, GARCHING, Germany 7Advanced Research Laboratories, Tokyo City University, TOKYO, Japan 8Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet, MUENCHEN, Germany Spins in gate-defined quantum dots (QD), as for example shown in Fig. 1(a), are currently discussed as one of the most promising scalable qubit architecture. Since the identification of the hyperfine interaction as a dominant spin qubit decoherence mechanism, 28Si/SiGe heterostructures have been receiving steadily increasing attention for realizing devices almost free of nuclear spin carrying isotopes. In this contribution, we report on the materials development and device realization of QDs in isotopically refined Si/SiGe heterostructures grown with molecular beam epitaxy. In a first generation our 28Si quantum Wells (QW) contained a concentration of residual 29Si smaller than 103 ppm [1]. With a new source material, we have very recently enhanced this value to 60 ppm of residual 29Si. The decoherence time in such isotopically engineered heterostructures is expected to be governed by electronic noise. A non-negligible source of electronic noise in the material may be induced by charge fluctuations in the vicinity of the qubit. We discuss the control of charge fluctuations in the two most relevant heterostructure concepts: first, modulation doped QWs and second, undoped structures with field-effect-induced charge carrier accumulation. The main challenge in the modulation-doped structures is the control and suppression of dopant related charge noise. We have experimentally studied band-structure engineering and the efficient use of a global top-gate to minimize these effects. We demonstrate stable single (Fig. 1(c)) and double QDs which can be tuned down to the few electron regime in a 28Si/SiGe heterostructure [1] and characterize the valley splitting. In the undoped field-effect-activated structures (Fig. 1(b)) we have investigated the role of the dielectric and of material interfaces in the occurrence of charge noise. We explore the advantages of the use of hybrid heterostructures with single crystalline insulator layers. [1] A. Wild, J. Kierig, J. Sailer, J. W. Ager, E. E. Haller, G. Abstreiter, S. Ludwig, D. Bougeard, APL 100,14,143110 (2012). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285837_tsqSRzUA0Y.jpg Caption 1: (a) SEM image of a QD device, (b) side view of a device based on an undoped 28Si/SiGe heterostructure, (c) Coulomb blockade in a 28Si-QD device 5 - Poster session Poster presentation 054 Measurement of charge states in Si/SiGe multiple quantum dots T. O. Otsuka1, K. Takeda1, J. Yoneda1, T. Honda2, M. R. Delbecq1, G. Allison1, M. Marx1, T. Nakajima1, T. Kodera2, S. Oda2, Y. Hoshi3, N. Usami4, K. M. Itoh5, S. Tarucha1 1RIKEN, WAKO, Japan 2Tokyo Institute of Technology, TOKYO, Japan 3University of Tokyo, TOKYO, Japan 4Nagoya University, NAGOYA, Japan 5Keio University, YOKOHAMA, Japan Electron spins in Si quantum dots (QDs) have long coherence times and have been considered good candidates for quantum bits in quantum information processing [1]. To realize quantum algorithms based on Si quantum dots, scaling up the quantum dot system is important as well as improvement of the single or two qubit operations. We fabricate Si/SiGe multiple quantum dot devices and measure the charge stability diagram. We fabricate triple and quadruple QD (TQD, QQD) devices on a Si/SiGe quantum well wafer. The QDs are formed by two layers of metal gates insulated by Al2O3 on the wafer surface. The wafer is undoped and carriers are induced by positively biasing the top global gate electrode. The confinement potentials of the QDs are formed by negatively biasing bottom fine gates. The QDs couple in series and are connected to reservoirs at both ends of the QD array.

We measure direct currents through the QD array. When we form a double QD (DQD), a honeycomb structure, which is characteristic for a DQD, is observed (Fig. (a)). The DQD contains many electrons and the inter dot tunnel coupling appears large. When we form a TQD, Coulomb peaks corresponding to a multiple QD are observed. There are three kinds of slopes in the charge transition lines supporting formation of the TQD. By decreasing the size of the device and optimizing the gate electrode geometry, we will be able to reduce the number of electrons in the QDs and demonstrate spin operations in Si/SiGe multiple QD devices. [1] F. A. Zwanenburg, et al., Rev. Mod. Phys. 85, 961 (2013). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286041_PzKHiIoLbl.png VII - Session VII: Ensemble donors and acceptors Oral presentation 060 Advances in Precision for Digital STM Lithography on Silicon H G Owen, J. B. Ballard, E Fuchs, S. W. Schmucker, C. Delgado, J.N. Randall, J. Von Ehr Zyvex Labs LLC, RICHARDSON, TEXAS, United States of America Hydrogen depassivation lithography has enabled unprecedented sub-nanometer precision in the positioning of dopant atoms in silicon,[1] advancing the field of silicon quantum electronics. However, as donor-based QIP devices scale from single-qubit devices towards multi-qubit devices such as crossbar architectures[2], atomically precise lithography is required over increasingly large areas with improved reproducibility. After developing the ZyVector[TRADEMARK] automated STM lithography system with real-time piezo creep correction, we have previously demonstrated open-loop atomic precision patterning (i.e. lithography errors of less than one dimer row or pixel (Fig.1a)) over length scales up to 100 nm (Fig.1b). On scales up to 500 nm, the position errors were up to 2.5%, with hysteresis errors becoming more significant over larger areas. In this work, we address these errors while continuing to optimize the correction of piezo creep, and also correction of hysteresis. Comparisons between patterns written with and without real time positioning corrections will be offered (Fig.2). For movements within small areas, creep correction reduces positioning errors by more than 90%. Hysteresis corrections for further reducing open-loop position errors will be described. A method of closed-loop navigation further reduces positioning error; the pattern can be divided into write fields, within which precise patterning can be achieved. Write fields are then stitched through the use of deliberately written fiducial marks or recognition of previously written patterns. Thus, the precise patterning can be scaled over large areas. Taking all these techniques together, we present a set of design rules, which will allow for successful patterning from the single-atom to the micron scale, allowing fabrication of the next generation of dopant-based QIP devices. [1] Fuechsle, et al.”�Nat Nano 7 242-246 (2012) [2] C. D. Hill, et al.”�Science Advances 1 (2015) Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286053_pJAWRVYvxY.png Caption 1: Fig. 1 (a): Our lithography pixel: 2 Si dimers, 7.68 Å square. (b): A square box drawn with line width 1px. Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img2_286053_pJAWRVYvxY.png Caption 2: Fig.2: A test pattern of 5 squares up to 112px (86 nm), drawn with (a) and without (b) real-time creep correction applied. 5 - Poster session Poster presentation 090 Valley-enhanced fast relaxation of gate-controlled donor qubits in silicon

A. Palyi1, P. Boross2, G. Szechenyi2 1Budapest University of Technology and Economics, BUDAPEST, Hungary 2Eotvos University, BUDAPEST, Hungary Gate control of donor electrons near interfaces is a generic ingredient of donor-based quantum computing [1,2]. Here, we address the question: how is the phonon-assisted qubit relaxation time T1 affected as the electron is shuttled between the donor and the interface? We focus on the example of the `flip-flop qubit' [3], defined as a combination of the nuclear and electronic states of a phosphorous donor in silicon, promising fast electrical control and long dephasing times when the electron is halfway between the donor and the interface. We theoretically describe [4] orbital relaxation, flip-flop relaxation, and electron spin relaxation. We estimate that the flip-flop qubit relaxation time can be of the order of 100 microseconds, 8 orders of magnitude shorter than the value for an on-donor electron in bulk silicon [5], and a few orders of magnitude shorter (longer) than the predicted inhomogeneous dephasing time (gate times). All three relaxation processes are boosted by (i) the nontrivial valley structure of the electron-phonon interaction, and (ii) the different valley compositions of the involved electronic states. References: [1] Kane, Nature 393, 133 (1998) [2] Zwanenburg et al., Rev. Mod. Phys. 85, 961 (2013) [3] Tosi et al., arXiv:1509.08538 [4] Boross et al, arXiv:1602.03691 [5] Pines et al., Phys. Rev. 106, 489 (1957) 5 - Poster session Poster presentation 048 Silicon spin qubit as a probe for biological imaging S Perunicic, M. U. Usman, C. Hill, T Hall, C. L. Hollenberg The University of Melbourne, MELBOURNE, Australia The ability to directly image individual cases of bio-molecules defined by their native cellular environmental and molecular interactions, would enable direct insight into fundamental bio-processes. Current state-of-the-art technologies such as nuclear magnetic resonance [1] and x-ray femtosecond laser nano-crystallography [2] for the determination of atomic structure of molecules are not only constrained by specimen’s properties i.e. crystallisation affinity, conformational homogeneity, and size, etc, but they also rely on averaging over large ensembles of molecules. General structure imaging in the single molecule domain is still an unsolved problem. In this work, we develop a novel method [3] for direct 3D magnetic resonance imaging (MRI) of a single molecule, based on quantum control and measurements of spin qubit probes, and particularly suited to donor spin qubits in silicon with long coherence times [4]. The method enables the donor electronic spin to act as a quantum probe that simultaneously performs the function of the MRI sensor and source of magnetic field gradient. The protocol is carefully designed to accumulate the signal corresponding to the molecule's nuclear spin density, encoded in dipole field gradient volumetric slices (Fig. 1a), on the quantum state of the donor spin. This information can be extracted by readout and transformed to produce a 3D Cartesian image of the molecular structure (Fig.1 b and c). The probe could be implemented by atomically precise placement of P donors in silicon [5]. Using realistic parameters, we show that it is possible to image the entire hydrogen and carbon sub-structure of a bio-molecule at the Angstrom level. The method thus provides a unique and realistic pathway for single-molecule imaging. References: [1] P. J. Judge et al., Methods Mol. Biol., 1261 (2015). [2] H. N. Chapman et al., Nature 470, 73 (2011). [3] V.S. Perunicic et al., Nat. Comm. (under review). [4] J. J. Pla et al., Nature 489, 541 (2012). [5] M. Fuechsle et al., Nat. Nano. 7, 242 (2012). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286023_VQlkf2n3Pw.png Caption 1: Overview: a)A target molecule above the 3-4nm deep donor. b) Test molecule. c) Simulated reconstruction of H1 & C13, resolution at 0.4-1.4 Angstroms

5 - Poster session Poster presentation 064 Spin Qubits in Ge Phononic Crystals G. Petukhov1, J. Boschee2, R.O. Oszwaldowski2, F. Vasko1, V. Hafyichuk1, V. N. Smelyanskiy3 1NASA Ames Research Center, MOUNTAIN VIEW, CALIFORNIA, United States of America 2South Dakota Tech, RAPID CITY, SD, United States of America 3Google Inc., VENICE, CALIFORNIA, United States of America We propose qubits based on shallow donor spins in germanium phononic crystals. Spin-lattice coupling of electrons in germanium, induced by the spin-orbit interaction, is in many orders of magnitude stronger than in silicon. In a uniform bulk material it allows to control the spins but causes very fast spin decoherence. However, the spin lifetime increases dramatically when the donor is placed into a quasi-2D phononic crystal and the Zeeman frequency falls within a phonon bandgap. In this situation single phonon processes are suppressed by energy conservation and the remaining two-phonon decay channel is very slow. Moreover, the Zeeman splitting can be fine tuned to induce a strong, long-range coupling between the spins of remote donors via exchange of virtual phonons. This, in turn, opens an efficient way to manipulate the qubits. We explore various geometries of phononic crystals in order to maximize the coherent qubit-qubit coupling while keeping the decay rate minimal. If the Zeeman frequency approaches the edge of the phonon gap the spin dynamics becomes non-Markovian and manifests itself in formation of collective spin-phonon states (dubbed as spin-polaritons) with large collective Lamb shift proportional to the square root of the donor concentration. 5 - Poster session Poster presentation 035 Theoretical considerations for quantum computation with donor spins in germanium G. PICA, B. Lovett UNIVERSITY OF ST ANDREWS, ST ANDREWS, United Kingdom We present detailed theoretical considerations about single and two-qubit operations with donor spins in germanium. The spin-orbit interaction of the donor electrons with the lattice nuclei is stronger, and the wavefunctions of the donor states larger, than in silicon crystals: we quantify the resulting greater tunability of the qubit energy splitting, which would enable a large reduction in the timescales needed for selective (local) coherent control of a donor spin in Ge as compared to Si. Furthermore, investigation of the peculiar structure of the lowest Ge conduction band reveals that the two-qubit exchange couplings in Ge can be intrinsically more robust against the unavoidable misplacements of the donors from their nominal positions. Thus, Ge-implanted donors promise both larger and more robust couplings than their respective Si-implanted counterparts, which significantly relaxes the constraints on both tight distances and precise positioning of the donor atoms.We develop a novel theory of the orbital state of a donor electron bound to any substitutional atom from the V group, that improves our previous multi-valley effective mass theory [1] by including the full plane-wave expansion of the Bloch states of the undoped germanium crystal - this proves to be crucial for a unified description across all donors. After the orbital energiesand the hyperfine couplings of Ge:P, Ge:As and Ge:Bi are fit with only two donor-dependent parameters, we are able to describe, with no further tunable parameters, the Stark physics induced by an external electric field. This leads us to a model of the tunability of the spin qubits under the most natural manipulation techniques [2,3,4]. The susceptibilities of both the hyperfine interaction strength and the electron g-factor as a function of the applied field are calculated, closely matching experimental values of the Stark shifts in Ge:As as measured by the Lyon group [A. Sigillito et al., to appear].We then calculate the Coulomb exchange couplings between adjacent donor spins, and quantify how much the tight distances required between silicon donors for significant couplingare relaxed by the larger wavefunctions of donors in germanium. More remarkably, we show that in some geometric configurations the relative variations of the couplings across realistic ranges of misplaced donors are much more contained than in silicon, which makes uniform control of large qubit clusters relatively more easy [5].With demonstrated millisecond spin coherence times [6], we hope that our calculations of the high speed of the electrical qubit manipulations and the advantages in two-qubit couplingmay raise interest in further experimental investigation of donors in germanium as a promising alternative to the more established framework of silicon quantum computing.

[1] G. Pica et al., Phys. Rev. B 90, 195204 (2014)[2] B. E. Kane, Nature 393, 133 (1998)[3] F. R. Bradbury et al., Phys. Rev. Lett. 97, 176404 (2006)[4] G. Wolfowicz et al., Phys. Rev. Lett. 113, 157601 (2014)[5] B. Koiller et al., Phys. Rev. Lett. 88, 027903 (2001)[6] A. Sigillito et al., Phys. Rev. Lett. 115, 247601 (2015) 5 - Poster session Poster presentation 088 Electric dipole spin resonance in systems with a valley dependent g-factor M.R. Rancic, G.B. Burkard University of Konstanz, KONSTANZ, Germany We theoretically investigate the electric dipole spin resonance (EDSR) in a single Si/SiGe quantum dot in the presence of a magnetic field gradient, e.g., produced by a micromagnet. The control of electron spin states can be achieved by applying an oscillatory electric field, which induces periodic oscillations in real space of the electron spininside the quantum dot. This motion inside a magnetic field gradient produces an effective periodic in-plane magnetic field, and allows for driven spin rotations near resonance. The magnetic field gradient induces a valley dependent g-factor and a valley dependent Rabi frequency. Our first goal is to quantitatively and qualitatively describe valley dependent g-factors and a valley dependent Rabi frequencies using a microscopic model. A valley dependent g-factor combined with inter-valley scattering gives rise to a novel electron spin decoherence mechanism. The second goal of our study is to describe the drop of coherence in the presence of inver-valley scattering, and furthermore, to discuss the interplay between valley and spin relaxation. All relevant decoherence mechanisms are quantitatively evaluated by solving a Lindblad master equation. Our results [1] are in agreement with recent experimental studies [2]. [1] Rančić, Marko J., and Guido Burkard. 'Electric dipole spin resonance in systems with a valley dependent g-factor.' arXiv preprint arXiv:1603.02829 (2016). [2] Kawakami, Erika, et al. 'Electrical control of a long-lived spin qubit in a Si/SiGe quantum dot.' Nature nanotechnology 9.9 (2014): 666-670. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_288071_JovqDkrcv1.png Caption 1: Probability for the echo sequence yielding the electron spin-up state. Comparison between experiment (blue circles) and theory (purple diamonds). VI - Session VI: Nano-electronic devices Oral presentation 025 A split accumulation gate architecture for silicon MOS quantum dots S. R. Rochette1, M. Rudolph2, A-M Roy1, G. A. T. A. Ten Eyck2, M.J. Curry2, J.P. Dominguez2, R.P. Manginell2, T. Pluym2, J. King Gamble3, M.P. Lilly4, C. Bureau-Oxton1, M.S. Carroll2, M. Pioro-Ladrière1 1Université de Sherbrooke, SHERBROOKE, Canada 2Sandia National Laboratories, ALBUQUERQUE, NM, United States of America 3Center for Computing Research, Sandia National Laboratories, ALBUQUERQUE, NM, United States of America 4Center for Integrated Nanotechnologies, Sandia National Laboratories, ALBUQUERQUE, NM, United States of America We introduce a split accumulation gate architecture for silicon metal-oxide-semiconductor (MOS) quantum dots, with a reduced electrode count for efficient scalable 1-D lay-out. The devices are fabricated with a foundry-compatible subtractive process (i.e. no lift-off processing) and a single poly-silicon gate stack. We demonstrate few-electron occupation in a single quantum dot with charging energies of the order of 8 meV. Magnetospectroscopy is used to measure singlet-triplet splittings of the order of 100 ueV. A detailed study of the tunneling rates, measured by both transport spectroscopy and single-shot radio-frequency charge sensing, is presented. By energizing two adjacent split accumulation gates, we form a double quantum dot with finite tunnel coupling at the (1,0) to (0,1) interdot charge

transition. The simplicity of the split accumulation gate architecture, combined with its tunability, makes it a promising canvas for increasing yield in MOS and other accumulation-mode (Si/SiGe, GaAs/AlGaAs) spin-qubit implementations. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285979_e6RAfHQPBI.jpg Caption 1: Few electron double quantum dot stability diagram and magnetospectroscopy of the 0-1 and 1-2 transitions of the left dot VI - Session VI: Nano-electronic devices Oral presentation 037 Precise GHz single-electron pumping with metal-oxide-semiconductor silicon quantum dots AR Rossi1, FEH Hudson2, MM Mottonen3, S. Rogge2, ASD Dzurak2, GCT Tettamanzi2 1University of Cambridge, CAMBRIDGE, United Kingdom 2University of New South Wales, SYDNEY, Australia 3Aalto University, HELSINKI, Finland On-demand transfer of single electrons at sub-nanosecond timescales via semiconductor quantum dots has attracted great interest in the broad context of quantum technologies. While this technique has been initially developed to enable a quantum realization of the unit ampere, more recently it has proved to be key for the emerging field of fermionic quantum optics and it could become instrumental for the upscaling of future solid-state quantum computers. At present, charge transfers with the lowest uncertainty have been achieved with GaAs quantum dot-based pumps [1]. However, in order to optimally operate these devices, demanding experimental conditions are required, such as very large perpendicular magnetic field, millikelvin temperature, and, in some case, specially tailored waveform of the driving signal [2]. Silicon implementations promise to significantly simplify these operation requirements in light of the mature metal-oxide-semiconductor (MOS) technology offering excellent control of the electrostatic confinement. Here, we discuss a silicon MOS quantum dot-based pump with a compact as well as flexible gate layout. By improving upon our previous device design [3], we have achieved a tighter electrostatic confinement and charging energies in excess of 30 meV in the few-electron regime. However, the reduced spatial separation between the device gates has come at the cost of stronger capacitive cross-couplings, with the result that each individual gate can largely affect tunnel barrier transparencies, dot electron number, and lateral confinement at once. In our experiments, by exploiting the high sensitivity of the pumping mechanism at different operation points, we have been able to probe the effect of each gate potential on the overall electrostatic landscape. This has led us to achieve fast and precise single-electron transfers at temperature as high as 4K and frequency in excess of 3.5 GHz by using a single-harmonic driving signal. The robustness of the pumping mechanism is confirmed by the evaluation of random uncertainties below 2 parts per million for variations of the experimental gate voltages of several tens of mV. [1] F. Stein et al., Appl. Phys. Lett. 107, 103501 (2015). [2] S.P. Giblin et al., Nature Comm. 3, 930 (2012). [3] A. Rossi et al., Nano Lett. 14, 3405 (2014). 5 - Poster session Poster presentation 021 Spin-cavity longitudinal coupling for two-qubit gates and measurement of protected spin qubits RR Ruskov (Hristov)1, C. Tahan2 1Univ. of Maryland, Laboratory for Physical Sciences, COLLEGE PARK, United States of America 2Laboratory for Physical Sciences, COLLEGE PARK, United States of America We have studied the possibility of longitudinal coupling of various encoded quantum dot spin-qubits to a microwave

resonator via modulation of voltage gates. A dynamical coupling of tens of MHz can be achieved. We investigate specific procedures for entangling gates using accumulated geometrics phases and calculate possible gate times and fidelities. Implications for qubit readout and continuous quantum monitoring are also considered. V - Session V: Quantum dot qubits Oral presentation 053 Electron g-factor of valley states in Si quantum dot qubits: interface physics and magnetic field angular dependence RR Ruskov (Hristov)1, C. Tahan2 1Univ. of Maryland, Laboratory for Physical Sciences, COLLEGE PARK, United States of America 2Laboratory for Physical Sciences, COLLEGE PARK, United States of America We present a theory of the electron g-factor in silicon quantum dots, that are manipulated by applied electric field [1]. The approach is based on modified effective mass equations with new spin-valley boundary conditions, derived from the interface symmetry. The valley state g-factor’s sign and size is explained via the interface-induced spin-orbit Rashba and Dresselhaus 2D interactions, that include both valley-mixing and valley-diagonal contributions. Compatibility with the experiment [1] requires much stronger valley-mixing contributions in Si, suggesting that bulk contributions (due to so-called non-parabolicity effects) are negligible. The effects of interface roughness, that have played a major role in the description of the so-called “relaxation hot spots”in such quantum dots [2], are shown here to be small. The predicted g-factor angular dependence on the magnetic field direction suggests that in a future experiment one can measure the relative weight of the Rashba and Dresselhaus terms. In particular, if Dresselhaus terms are dominating, one can predict decoherence “sweet spots”with respect to the in-plane magnetic field direction that are generally different for the 1e- and 3e- QD spin qubits. Electrical g-factor control opens the possibility of fast and all-electric manipulation of a few electron spin-qubit, without the need of a nanomagnet or a nuclear spin-background. [1] M. Veldhorst, R. Ruskov, C.H. Yang, J.C.C. Hwang, F.E. Hudson, M.E. Flatté, C. Tahan, K.M. Itoh, A. Morello, and A. S. Dzurak, Phys. Rev. B 92, 201401 (R), (2015) [2] C. H. Yang, A. Rossi, R. Ruskov, N. S. Lai, F. A. Mohiyaddin, S. Lee, C. Tahan, G. Klimeck, A. Morello, and A. S. Dzurak, Nature Communications 4, 2069, pp. 1-8, (2013) 5 - Poster session Poster presentation 089 Charge noise double sweet spot MR Russ, GB Burkard University of Konstanz, KONSTANZ, Germany The resonant exchange (RX) qubit is a variation of the exchange-only spin qubit implemented in a (linearly arranged) triple quantum dot which responds to a narrow-band resonant frequency and has recently been under intense scrutiny as a qubit for spin-based quantum computation. Here, we show the existence of double “sweet spots,”[1] where the qubit is least susceptible to noise. Our noise model includes charge noise in each quantum dot giving rise to two independent (noisy) bias parameters ε and εM. We calculate the energy splitting of the two qubit states as a function of these two bias detuning parameters to find sweet spots. Our investigation shows that such sweet spots exist within the low-bias regime, in which the bias detuning parameters have the same magnitude as the hopping parameters (Fig.1 (a)). The location of the sweet spots in the (ε,εM) plane depends on the hopping strength and asymmetry between the quantum dots. In the regime of weak charge noise, we identify a new favorable operating regime for the RX qubit based on these double sweet spots compared to the traditional regime. [1] M. Russ and G. Burkard, Phys. Rev. B, 91, 235411 (2015) Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_288107_M4t8PexUSx.png Caption 1: Position of a the double sweet spots (DSSs), the RX regime and the exchange-only qubit.

5 - Poster session Poster presentation 099 Strained Ge quantum wells towards Ge spin-qubits DS Sabbagh1, A. Sammak1, L.A. Yeoh1, L. Di Gaspare2, M. De Seta2, G. Capellini3, G. Scappucci1 1TU Delft, DELFT, The Netherlands 2Università Roma TRE, ROME, Italy 3IHP-microelectronics, FRANKFURT (ODER), Germany Over the past two decades, most research into group IV heterostructures has focused on the 2D electron gas obtained at the interface between strained Si and silicon-rich, relaxed Si1-xGex (x~0.2 to 0.3). Drastic improvements in material quality by moving to undoped enhancement-mode heterostructures, along with integration of isotopically enriched 28Si, make Si quantum wells the workhorse for quantum computing architectures. At the other end of the alloy composition range, research into germanium-rich Ge/Si1-xGex heterostructures (x~0.7 to 0.9) is still in its infancy. The following points justify interest in strained Ge quantum wells for quantum computing applications: the expected electron and hole mobilities larger than in Si; the possibility of long electron spin coherence times by isotope purification; the larger Bohr radius of a bound electron in Ge compared to Si due to the larger dielectric constant and smaller effective mass, which, in principle should relax nanofabrication challenges for making qubits; the possibility of an all-electrically controlled qubit due to larger spin-orbit coupling. Here we report progress in developing Ge/SiGe materials towards Ge based spin-qubits. In particular, we demonstrate growth in a UHV-CVD system of electron-doped strained Ge/SiGe multi-quantum wells of high structural quality. We also show progress in transferring growth process developed in UHV-CVD to an industrial-like RP-CVD tool with a 4”wafer setup. III - Session III: Quantum processor architectures Oral presentation 028 Quantum Simulation of the Hubbard Model with Dopant Atoms in Silicon J Salfi1, J Salfi1, B Voisin1, J Bocquel1, J. A. Mol1, A Tankasala2, M Usman3, R. Rahman2, G Klimeck2, B C Johnson3, J C McCallum3, M Y Simmons1, L C L Hollenberg3, S Rogge1 1The University of New South Wales, SYDNEY, Australia 2Purdue University, WEST LAFAYETTE, United States of America 3University of Melbourne, VICTORIA, Australia Simulating many-body quantum physics on classical hardware is difficult because the required computing resources scale exponentially with system size[1]. Quantum simulation (QS), a fast-growing field in quantum science, offers a workaround by replacing the classical hardware with a many-body quantum system. For instance, simulating the Hubbard model, a lattice of interacting fermions, is an exciting frontier due to the Hubbard model’s connection with quantum states such as unconventional superconductivity that challenge our understanding of nature. However, simulating the Hubbard model is very difficult. For circuit-based quantum simulation[2], many qubits and complex sequences of gate operations are required. This complexity is avoided in experiments based on cold atoms in optical lattices mimicking directly the Hubbard model. However, local measurements and cooling to the quantum regime remain very problematic[3]. Recently, we performed a quantum simulation of a two-site Hubbard model with interacting dopant atoms in silicon, which mimics directly an isolated valence bond[4]. This was accomplished by atomic resolution spatial tunneling spectroscopy in the single-electron regime[5]. The coupled-spin spectrum and the quasi-particle wave-functions were measured in the quantum regime (resolving spin states), from which we directly determine that the states are interacting. Interference processes of atomic orbitals were observed in real space, from which the entanglement entropy (EE) and Hubbard interactions were quantified. This is remarkable since EE is a fundamental quantity of many-body phases that has hitherto not been measured for interacting Fermions[6]. We find that the EE and Hubbard interactions increase with increasing dopant separation, and the latter are non-perturbative, as desired to simulate exotic many-body states[7]. Finally, we review capabilities for simulating larger Hubbard systems. Hydrogen-

resist lithography allows us to place dopants in the silicon crystal with atomic precision. Moreover, electrostatic gate control of single dopants has been demonstrated in-situ, towards control of filling factor. Finally, a quantum dot can be locally formed underneath the tip, to realize a local probe that could be used for local spin readout. These results establish dopants in silicon as a promising system for large scale simulation of the Hubbard model in the quantum regime. References [1] Georgescu et.al Rev.Mod.Phys. 86 153-185 (2014). [2] Lanyon et.al, Science 334 57-61 (2011). [3] Greif et.al, Science 340 1307-1310 (2013). [4] Salfi et.al, accepted in Nature Comms (2016), arxiv:1507.06125. [5] Salfi et.al, Nature Mat. 13 605-610 (2014). [6] Amico et.al, Rev.Mod.Phys 80, 517-576 (2008). [7] Gull et.al, Phys.Rev.Lett. 110 216405 (2013). 5 - Poster session Poster presentation 098 Towards Long-distance Spin Qubit Coupling Through High Kinetic Inductance Superconducting Nanowire Resonators N. S. Samkharadze1, G. Zheng1, N. Kalhor1, A. Bruno1, P. Scarlino1, D. P. DiVincenzo2, L. DiCarlo1, L.M.K. Vandersypen1 1TU Delft, DELFT, The Netherlands 2JARA Institute for Quantum Information, RWTH Aachen University, AACHEN, Germany The long lived qubits based on electron spins in Silicon quantum dots show great promise as elementary building blocks of a quantum processor. Proposals have been put forward for incorporating these qubits in circuit QED architecture as a means of scaling. However, the achievement of the strong coupling regime between spin qubits and superconducting resonators is facing two main challenges: First, due to small dipole moments of electrons confined to quantum dots, the interaction strength between electrons and superconducting resonators tends to be weak. Second, the performance of superconducting resonators tends to degrade in high magnetic field, which is required for operation of spin qubits. We present a new design of high quality-factor superconducting microwave resonators, based on NbTiN nanowires, which addresses both of these issues [Phys. Rev. Applied 5, 044004 (2016)]. Our nanowire resonators retain intrinsic quality factors of over 10^5 while subjected to in-plane magnetic fields up to 6 T. Moreover, the high kinetic inductance of the strongly disordered NbTiN nanowires serves to maximize the characteristic impedance of the resonators, and they are expected to develop an order of magnitude higher vacuum fluctuation voltages compared to the standard coplanar waveguide resonators. Next experiments will focus on achieving strong coupling between a nanowire resonator and a single electron spin in a gate-defined double quantum dot in Si/SiGe heterostructure. IV - Session IV: Quantum dots and nanowires Oral presentation 008 Pauli blockade in a few-hole CMOS double quantum dot M. Sanquer1, H. Bohuslavskyi2, A. Corna1, D. dr. Kotekar-Patil1, R. dr. Maurand1, S. dr. Barraud2, X. dr. Jehl1, S. dr. De Franceschi1 1CEA-Grenoble and UGA, GRENOBLE, France 2CEA-LETI, GRENOBLE, France Although their advantage for electrically driven spin-orbit qubit very few cases of hole double quantum dots in silicon have been reported to date [Li et al. Nanoletters 15, 7314 (2015)] though none of them in the few hole regime. We fabricated two coupled hole quantum dots in series using 11nm thick silicon on insulator nanowire and a CMOS process line ( 4 1024 Boron m-3 channel doping, 2.5nm SiO2 -1.9nm HfSiON - 5nm ALD TiN gate stack, self-aligned 15nm thick nitride spacers, self-aligned source and drain, etc.). The two dots have a footprint of 18×30 nm2 and the

addition energy reaches 100meV in the few-hole regime. The first hole in each dot is detected by a tunnel current thanks to large tunneling enhancement at strong drain-source bias (Vds=200mV). The double dot can be also tuned in the high hole density case where the stability diagram is detected at moderate Vds . The stability diagram is well understood taking into account the excellent control of each dot by its accumulation gate. In the few-hole regime, Pauli blockade is found for (1,1)/(0,2) equivalent charge transitions. Its phenomenology differs from the one for electron doubled quantum dots due to the underlying presence of strong spin-orbit coupling (see figure): a sharp dip in tunneling current is found at small magnetic field (below 10mT). This dip is consistent with a magnetic field induced lifting of the Pauli blockade as expected in presence of strong spin-orbit coupling [Danon et al. PRB 80, 041301(2009)]. The typical magnetic field scale for the dip at small field is comparable to the one observed for holes in InSb nanowires [Pribiag et al. Nature Nano 8, 170 (2013)] and smaller than in previous report for holes in silicon DQD[ Li et al. Nanoletters 15, 7314 (2015)] . This dip extends to detuning energy between the ground states of the two dots up to several meV, indicating that the S(0,2h)-T(0,2h) splitting is very large in our hole quantum dots. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285868_fpxYp7QU3T.png Caption 1: Drain-source current vs(detuning energy, B) in the hole DQD for the (3,3)�(2,4) transition at Vd=-100mV and T=60mK. VI - Session VI: Nano-electronic devices Oral presentation 022 Theory of Corner States in Silicon Nanowire Devices AS Saraiva1, MF dr Friesen2, BK prof Koiller1, MFGZ dr Gonzalez-Zalba3 1UFRJ (Universidade Federal do Rio de Janeiro), RIO DE JANEIRO, Brazil 2University of Wisconsin, MADISON, United States of America 3Hitachi Cambridge Lab, CAMBRIDGE, United Kingdom Nanowire-based transistors, such as FinFETs and Tri-gate FETs, form one and zero dimensional states at the corners. These corner states may be manipulated for quantum electronic applications, such as tunable quantum dot-based spin qubits. We discuss the electronic structure of the electrons bound at the corner, considering the effects due to the anisotropy of the effective mass, the splitting of valleys due to the confinement and the scattering at the interface, generalizing our results to corners of arbitrary angle. Our results indicate the optimal conditions for lifting the valley degeneracy, known to impact quantum coherence and control. We finally mention the expected impacts of this geometry on the tunnel and exchange coupling between dots at opposite corners of a wire. 5 - Poster session Poster presentation 051 Simulation of micro-magnet stray-field dynamics for spin qubit manipulation in isotopically purified silicon L. R. Schreiber, R. Neumann RWTH Aachen University, AACHEN, Germany An electron spin localized in a nuclear-spin free host material e.g 28Si exhibits very long dephasing times beyond 10 ms and is thus suitable for representing a quantum bit [1]. Manipulation of such a qubit can be done all-electrically by electric dipole spin resonance. If silicon is used as the host material, a gradient magnetic field across the quantum dot is required, in order to strongly couple an AC electric field to the spin qubit [2, 3]. This gradient magnetic field can be generated by a micro-magnet fabricated on top of the silicon sample. Thermal fluctuations of its magnetization, however, might limit the coherence time of the spin qubit [4]. Therefore, we simulated the thermal fluctuations of a cobalt micromagnet at 100 mK and in an external magnetic field of 500 mT by the stochastic Landau-Lifshitz-Gilbert equation [5]. For the simulations we used a typical device geometry (Fig. 1A) of a metallic gate defined double quantum dot in a Si/SiGe heterostructure with a cobalt micro-magnet on top [2]. From the quantum noise spectral density of the magnetic stray-field at the position of the double

quantum dot (Fig. 1B) the spin relaxation time T1 and dephasing time T2 of the spin qubit solely due to the stray-field fluctuations are calculated. While the micro-magnet fluctuations have only a small effect on the dephasing (T2 > 50 s), it limits the qubit relaxation time. The shortest T1 we calculated is 3 s. Furthermore, we investigated the scalability of the ansatz by calculating the addressability error in a double dot hosting two qubits, i.e. the error due to off-resonant driving of the neighboring qubit [5]. The examined device enables a Rabi frequency of 15 MHz with an addressability error (probability of an unintentional spin flip of the neighboring qubit) below 10-3. The addressability error can be further reduced by sophisticated pulse shaping. [1] M. Veldhorst et al., Nat. Nanotechnol 9, 981 (2014). [2] K. Takeda et al., arXiv:1602.07833v1 (2016). [3] E. Kawakami et al., arXiv: 1602.08334v1 (2016). [4] A. Kha et al., Appl. Phys. Lett. 107, 172101 (2015). [5] R. Neumann and L. R. Schreiber, J. Appl. Phys. 117, 193903 (2015). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286032_1BLYYSKxmF.gif Caption 1: Fig. 1: (A) Electrostatically defined double quantum dot (red dots) in the Si/SiGe quantum well and Co micro-magnet geometry investigated. (B) Quantu 5 - Poster session Poster presentation 047 Top-down fabricated silicon nanowire junctionless transistors FJS Schupp1, MMM Mirza2, DAM MacLaren2, GADB Briggs1, JAM Mol1, DJP Paul2 1University of Oxford, OXFORD, United Kingdom 2University of Glasgow, GLASGOW, United Kingdom Top-down fabricated silicon nanowire junctionless transistors Felix J. Schupp1”�, Muhammad M. Mirza2, Donald A. MacLaren3, Andrew A. D. Briggs1, Jan A. Mol1 and Douglas J. Paul2 1 Department of Materials, University of Oxford, Oxford OX13PH, UK 2 School of Engineering, University of Glasgow, Glasgow G12 8LT, UK 3 SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK “� felix.schupp@materials.ox.ac.uk Silicon nanowires have potential uses in a wide range of devices and applications including transistors, qubits, photovoltaics, thermoelectric generators, and photodetectors. Understanding the electronic transport properties of nanowires is therefore essential for the optimization and fabrication of high performing devices. Nanowire transistors made from an etched (quasi-)one-dimensional silicon channel that is covered by a wrap-around gate, provide better electrostatic control of the channel than planar or tri-gate transistors and further mitigate short-channel effects. If scaled sufficiently such that quantum confinement dominates over thermal energy, these transistors have the potential for room temperature single-electron transport. To date, the most advanced nanowire transistor design consists of an undoped channel connected to a heavily doped source and drain contact, and operates in accumulation mode[1]. I will present nanowire transistors that operate in depletion mode and consist of a junctionless nanowire with uniform doping concentration in the channel and source/drain contacts. Our silicon nanowires are etched from a 55 nm SOI substrate with a phosphorous doping concentration ND = 4x1019 cm-3. Thermal oxidation of the etched nanowires reduces the channel diameters down to 8 nm, with a gate oxide of 16 nm[2]. An aluminium gate is then used to deplete the channel of charge carriers. While the doping concentration in the channel exceeds the Mott transition (NMott = 3.5x1018 cm-3) we are still able to effectively pinch-off the channel at room temperature. We attribute the observed transistor behaviour to the (quasi-)one-dimensional nature of our silicon nanowires, which inhibits three-dimensional screening[3]. This interpretation is further substantiated by the temperature and bias-voltage dependence of the low-bias conductance, which is consistent with a one-dimensional disordered channel. Finally, we observe signatures of quasi-ballistic transport at milli-Kelvin temperatures that are consistent with the higher temperature data. Our experimental results shed light on the role of dimensionality in ultra-scaled top-down silicon nanowire transistors and emphasise the importance of disorder in these devices. Ultimately, top-down etched silicon nanowires could form the basis for a silicon technology in reduced dimensions with operation at room temperature. [1] R. Lavieville, S. Barraud, A. Corna, X. Jehl, M. Sanquer, and M. Vinet, “350K Operating Silicon Nanowire Single Electron / Hole Transistors Scaled Down to 3.4nm Diameter and 10nm Gate Length,”IEEE conference paper, pp. 9-12, 2015.

[2] M. M. Mirza, H. Zhou, P. Velha, X. Li, K. E. Docherty, A. Samarelli, G. Ternent, and D. J. Paul, “ Nanofabrication of high aspect ratio (50:1) sub-10nm silicon nanowires using inductively coupled plasma etching,”Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, vol. 30, no. 6, p. 06FF02, 2012 [3] M. M. Mirza, D. A. MacLaren, A. Samarelli, B. M. Holmes, H. Zhou, S. Thoms, D. MacIntyre, and D. J. Paul, “Determining the Electronic Performance Limitations in Top-Down-Fabricated Si Nanowires with Mean Widths Down to 4 nm.,”Nano letters, vol. 14, pp. 6056-60, Nov. 2014 Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286015_U2ixWepEIP.png Caption 1: Left: Current as a function of Gate voltage through 4e19 phosphorous doped NWs. Right:TEM cross section of a silicon nanowire with wrap-around gate. 5 - Poster session Poster presentation 004 Charge-noise-insensitive gate operations for always-on, exchange-only qubits Y.-P.S Shim, C. T. Tahan Laboratory for Physical Sciences, COLLEGE PARK, United States of America Encoded qubit in a triple quantum dot allows for exchange-only implementation of all gate operations. But during exchange the charge and spin degrees of freedom are coupled, leaving qubit gates susceptible to charge noise. The resonant exchange (RX) qubit offers a partial sweet spot to charge noise but requires either microwave control or moving away from the sweet spot to perform a full set of qubit operations. The 'symmetric operating point' offers a dynamical sweet-spot for pair-wise exchange interactions, but still requires many pulses to do a single two-qubit gate. We present an always-on, exchange-only qubit that offers a true sweet spot to charge noise on the quantum dot energy levels [1]. Further, our qubit system allows for all single- and two-qubit gate operations to be done at sweet spots using only DC-pulses to tune the couplings between the dots, while only taking one pulse for an encoded two-qubit entangling operation. We discuss how to interconvert this always-on, exchange-only qubit to other exchange-only qubits as a new resource for computation and communication. [1] Yun-Pil Shim and Charles Tahan, arXiv:1602.00320. VII - Session VII: Ensemble donors and acceptors Oral presentation 044 Large Stark effect for donor electron spins in germanium A. J. Sigillito1, A. M. Tyryshkin1, C. C. Lo2, J. W. Beeman3, E. E. Haller3, K. M. Itoh4, S. A. Lyon1 1Princeton University, PRINCETON, United States of America 2London Centre for Nanotechnology, University College London, LONDON, United Kingdom 3Materials Sciences Division, Lawrence Berkeley National Laboratory, BERKELEY, United States of America 4School of Fundamental Science and Technology, Keio University, 3-14-1 HIYOSHI, KOHOKU-KU, YOKOHAMA, Japan Donor electron spins in germanium have recently been shown to support coherence times of milliseconds in isotopically enriched material containing less than 0.1% magnetic 73Ge nuclei [1]. While these times are short relative to donors in 28Si, germanium offers many advantages over silicon. In particular the large spin orbit coupling, small valley orbit splitting, and shallow donor depths lead to an extreme electric field tunability [2]. In this talk we report the first experimental values for the spin-orbit and hyperfine Stark shifts for 75As and 31P donor spins in germanium. We find that for donors in Ge, the Stark shift is dominated by the spin-orbit Stark effect. The shift depends strongly on the directions of the external electric and magnetic fields relative to the host crystal. In certain orientations, the spin-orbit Stark parameter is found to be five orders of magnitude larger than in silicon. Additionally, a large hyperfine Stark shift is resolved at select field orientations and is found to be an order of magnitude larger than in silicon. An effective mass theory developed by Pica et al. [3] is compared to these results and found to be in excellent

agreement. In this talk the angular dependences of the Stark effects will be reported and explained using a valley repopulation model. [1] A. Sigillito et al., Phys. Rev. Lett. 115, 247601 (2015) [2] R. Rahman et al., Phys. Rev. B 80, 155301 (2009) [3] G. Pica et al., in preparation III - Session III: Quantum processor architectures Oral presentation 076 A photonic link for donor spin qubits in silicon S. Simmons1, K. Morse1, R. Abraham1, P. Becker2, N. V. Abrosimov3, H. Riemann3, H.-J. Pohl4, M. Thewalt1 1Simon Fraser University, BURNABY, Canada 2PTB Braunschweig, 38116, BRAUNSCHWEIG, Germany 3Leibniz-Institut für Kristallzüchtung, 12489, BERLIN, Germany 4VITCON Projectconsult GmbH, 07743, JENA, Germany Atomically identical donor spin qubits in silicon offer excellent native quantum properties, which match or outperform many qubit rivals. To scale up such systems it would be advantageous to connect silicon donor spin qubits in a cavity-QED architecture. Many proposals in this direction introduce strong electric dipole interactions to the otherwise largely isolated spin qubit ground state in order to couple to superconducting cavities. Here we present an alternative approach, which uses the built-in strong electric dipole (optical) transitions of singly-ionized double donors in silicon. These donors, such as chalcogen donors S+, Se+ and Te+, have the same ground-state spin Hamiltonians as shallow donors yet offer mid-gap binding energies and mid-IR optical access to excited orbital states. This photonic link is spin-selective which could be harnessed to measure and couple donor qubits using photonic cavity-QED. This approach should be robust to device environments with variable strains and electric fields, and will allow for CMOS-compatible, bulk-like, spatially separated donor qubit placement, optical parity measurements, and 4.2K operation. We will present preliminary data in support of this approach, including 4.2K optical readout in Earth’s magnetic field, where long T1/T2 times have been measured. 5 - Poster session Poster presentation 068 G-factor anisotropy of holes in planar silicon quantum dots PC Spruijtenburg, S.V. Amitonov, W.G. Van der Wiel, F.A. Zwanenburg University of Twente, ENSCHEDE, The Netherlands Holes in silicon have several interesting properties that make it a strong candidate for use in quantum computation. Spin-orbit coupling, manifesting in the g-factor and the heavy-hole/light-hole bands, is key towards this goal. Spin-orbit interaction can facilitate coherent oscillations of individual hole spins through electric-dipole spin resonance (EDSR), as demonstrated in e.g. InAs nanowires[1]. The spin quantization axis of heavy holes in planar quantum wells is predicted to have a strong preference for alignment parallel to the confinement axis because of spin-orbit coupling. This directly results in anisotropy of the g-factor[2]. Experimental verification of this for holes in silicon planar quantum dots has thus far been missing. In our work we demonstrate what is likely the last charge transition of a stable hole quantum dot in silicon. Magnetospectroscopy of this charge transition shows a clear Zeeman splitting dependent on the direction of the magnetic field. Figure 1 shows the conductance of the quantum dot varying with the magnetic field rotating from in-plane to out-of-plane over angle φ with |B|= 1 T. A maximum Zeeman splitting is reached with the magnetic field pointing out-of-plane (φ= (n+1/2)π). A simple model of the Zeeman splitting composed of an independent in-plane and out-of-plane g-factor fits the data remarkably well and we extract an out-of-plane g-factor g⏊ ~ 3.5 and an in-plane g-factor of g”- ~ 2.1. This enhancement of the g-factor for out-of-plane magnetic orientations is consistent with the interpretation of preferred spin-orientations in the quantum well. 1. Nadj-Perge, S., Frolov, S. M., Bakkers, E. P. A. M. & Kouwenhoven, L. P. Spin-orbit qubit in a semiconductor

nanowire. Nature 468, 1084-1087 (2011). 2. Winkler, R., Culcer, D., Papadakis, S. J., Habib, B. & Shayegan, M. Spin orientation of holes in quantum wells. Semicond. Sci. Technol. 23, 114017 (2008). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286082_9nBxreYMtL.png Caption 1: Conductance as a function of magnetic field angle and source-drain bias Vs. |B| = 1 T III - Session III: Quantum processor architectures Oral presentation 046 Circuit QED-based approaches for entangling distant resonant exchange qubits in silicon V. Srinivasa1, J. M. T. Taylor2, C. T. Tahan3 1Laboratory for Physical Sciences/University of Maryland, College Park, COLLEGE PARK, United States of America 2Joint Center for Quantum Information & Computer Sci/Joint Quantum Institute/NIST, GAITHERSBURG, MD, United States of America 3Laboratory for Physical Sciences, COLLEGE PARK, MD, United States of America Realizing robust entanglement of coherent qubits at macroscopic distances enables long-range gating and provides a pathway for achieving modularity in quantum information processing implementations. As a candidate system for this purpose, we investigate theoretically a hybrid quantum system consisting of spatially separated resonant exchange qubits, defined in three-electron semiconductor triple quantum dots, that are coupled via a superconducting transmission line resonator. Drawing on methods from circuit quantum electrodynamics and Hartmann-Hahn double resonance techniques, we analyze three specific approaches for implementing resonator-mediated two-qubit entangling gates in both dispersive and resonant regimes of interaction. We calculate entangling gate fidelities as well as the rate of relaxation via phonons for resonant exchange qubits in silicon triple dots and show that such an implementation is particularly well-suited to achieving the strong coupling regime. Our approach combines the favorable coherence properties of encoded spin qubits in silicon with the rapid and robust long-range entanglement provided by circuit QED systems. I - Session I: Single donors and acceptors Oral presentation 078 Measurement of the lifetime of bismuth donor orbital states in silicon N. Stavrias1, K Saeedi Ilkhchy2, P.T. Greenland3, B. Redlich2, B.N. Murdin4 1Radboud University, NIJMEGEN, The Netherlands 2FELIX Laboratory, Radboud University, NIJMEGEN, The Netherlands 3London Centre for Nanotechnology, University College London, LONDON, United Kingdom 4Advanced Technology Institute, University of Surrey, GUILDFORD, United Kingdom Donors in silicon are model ion trap systems with the potential for use in quantum information processing (QIP) applications [1]. The advantages of using such systems are the long orbital and spin coherence times [2,3]. The lifetime of the state sets the speed of the possible gate operations. Bi is the deepest of the shallow donors in Si unlike the other donor species the Bi Rydberg transitions lie above the Si phonon energies [4]. We present results of the lifetime of the orbital transitions of Bi donors in Si, measured using pump-probe spectroscopy through THz excitation provided by the FELIX free electron laser. Samples were measured under controlled temperature either in flowing He vapour or superfluid He. The orbital lifetimes obtained are consistent with those derived from the linewidths measured through FTIR. Using the pump-probe data as well as concurrent non-contact photo-conductive measurements, we were able to obtain information on the two main ionization processes, two-photon and thermal, giving an insight into these fundamental processes. This opens the possibility to lift the constraints on the separation of donor qubits by coupling them using the larger wavefunction extent of the higher excited states.

[1] Stoneham, A. M., et al. Journal of Physics: Condensed Matter, 15, L447 (2003) [2] Greenland, P. T., et al. Nature, 465, 1057-1061 (2010) [3] Steger, M., et al. Science, 336, 1280-1283 (2012) [4] Saeedi, K., et al. Scientific reports 5 (2015). V - Session V: Quantum dot qubits Oral presentation 052 AC Stark effect and optimal control of a strongly driven Si/SiGe quantum dot spin qubit K.T. Takeda1, J Kamioka2, J Yoneda1, T Otsuka1, M Delbecq1, G Allison1, T Nakajima1, T Kodera2, S Oda2, S Tarucha1 1RIKEN CEMS, WAKO, SAITAMA, Japan 2Tokyo Institute of Technology, TOKYO, Japan Electron spins in Si quantum dots are one of the most promising candidates for implementing qubits in solid-state quantum computing due to their long coherence time. Recently, high-fidelity control of single-electron spins using either ESR [1] or EDSR with a micro-magnet technique [2] has been reported. However, further enhancement of the qubit fidelity is desirable for the implementation of fault-tolerant multiple-qubit gates and quantum algorithms. Here we report the effect of strong microwave excitation of a Si/SiGe spin qubit with a micro-magnet inhomogeneous field gradient. To increase the qubit fidelity, it is straightforward to apply large microwave power to increase the Rabi oscillation frequency (fRabi) and therefore increase the number of possible operations within the coherence time. As the microwave power is increased, in addition to the increasing fRabi, we observe a shift of the centre resonance frequency, namely, an AC Stark effect. The largest observed shift is nearly 10 MHz, which is more than two orders of magnitude too large to be explained by the standard Bloch-Siegert shift (δf=fRabi

2/Ez<0.1 MHz for Ez~16 GHz and fRabi<40 MHz). A possible mechanism for the frequency shift is the asymmetric dot motion due to the anharmonicity of the quantum dot confinement. This can cause the effective shift of the dot position during the qubit driving, leading to a reasonably large centre resonance frequency shift due to the field gradient (δf~10 MHz for 1 nm displacement and 0.75 T/μm gradient). We finally discuss a way to reduce the phase error (or the qubit infidelity) caused by the frequency shift using either the dynamical Z control using the field gradient [3] or the quadrature control [4]. [1] M.Veldhorst et al., Nat. Nanotechnol. 9, 981-985 (2014). [2] K. Takeda et al., arXiv (2016) & E. Kawakami et al., arXiv (2016). [3] J. Yoneda et al., PRL 113, 267601 (2014). [4] E. Lucero et al., PRA 82, 042339 (2010). III - Session III: Quantum processor architectures Oral presentation 027 Scaling up a donor based silicon quantum processor ST Tenberg UNSW, KINGSFORD, Australia Donor spin qubits in silicon are excellent building blocks of a quantum computer due to their phenomenally long coherence times and high gate fidelities [1]. However, a scalable way to couple such qubits is still under investigation with several proposals placing a strong demand on fabrication techniques. In this talk, we will present a novel technique to achieve fast high-fidelity 2-qubit operations without precise donor placement, allowing for a scalable quantum processor [2]. Quantum information is encoded in either the electron-nuclear flip-flop states or the nuclear spin. The key element is the electric dipole formed by separating electron and donor with a dc bias produced by a gate located above the donor. Consequently not only the hyperfine interaction between electron and nucleus strongly depends on the applied electric fields, but also can the qubit interact with the electric field of a superconducting resonator (Fig. 2b) or the dipole field of another qubit hundreds of nanometres apart (Fig. 1b). Even though the qubit is now susceptible to electric fields, the dephasing due to charge noise can be as low as 0.1kHz and gate fidelities of 99.9% can be reached at certain bias gate voltages. These estimated errors fall within the fault-tolerance threshold of some quantum error correction protocols. A large number of qubits can then be interconnected in a network robust

against errors. Prototypical devices to demonstrate coupling between one qubit and a superconducting resonator (Fig. 2a) and direct dipolar two-qubit coupling (Fig. 1a) are fabricated. [1] J. T. Muhonen, et. al., Nature Nanotechnology 9, 986 (2014). [2] G. Tosi, et.al. arXiv:1509.08538 (2015). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img2_285984_FEgUhPpnSs.png Caption 1: FIG. 2. (a) Optical image of a microwave resonator. (b) Schematic of the qubits beneath the resonator. Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img1_285984_FEgUhPpnSs.png Caption 2: FIG. 1. (a) SEM image of a device for dipolar coupling of two qubits. (b) Schematic of two qubits’ interaction via their dipole field. 5 - Poster session Poster presentation 017 A robust Si:P nuclear spin quantum processor GT Tosi, F. A. M. dr. Mohiyaddin, S. T. Tenberg, V. S. Schmitt, A. Morello University of New South Wales, SYDNEY, Australia The record-long coherence times [1] and compatibility with CMOS industry makes the nuclear spin of a phosphorus donor in silicon the perfect candidate for a scalable quantum computer. However, a clear proposal for a multi-qubit processor that is compatible with current fabrication limitations is still missing. Here we completely redefine the way quantum gates are performed, with the resulting processor architecture being effective at larger inter-qubit distances and not requiring precise donor placement, therefore being achievable with current technology. The processor works with a global magnetic drive at GHz frequencies, and the electron of each donor biased half-way towards a silicon-oxide interface (Fig. 1a). In this region the electron-nucleus hyperfine interaction is extremely sensitive to electric fields, yielding a new 1-qubit drive scheme based on a Raman process (Fig. 1b), which is much faster than the usual NMR drive scheme. The microwave magnetic drive also decouples the qubit from electric noise, at a second-order clock transition point (Fig. 1c) that has its origins on an AC-Stark shift created by the drive. Finally, we propose two new types of long-distance 2-qubit gates (Fig. 1d) that are enabled by the nuclear-spin response to electric fields. The first one is due to the electric dipole-dipole interaction between two neighboring qubit cells, and is most effective at nm distances. The second one happens via a virtual photon in a microwave resonator, therefore enabling shuttling of quantum information on a chip. [1] J. T. Muhonen, et. al., Nature Nanotechnology 9, 986 (2014). [2] G. Tosi, et.al. arXiv:1509.08538 (2015). FIG. 1. (a) Single-qubit cell, showing electron wavefunction biased half-way towards interface. (b) Level diagram for Raman-drive of nuclear spin qubits, using two microwave fields. (c) Nuclear spin transition frequency as a function of applied vertical electric field, showing region where both first and second derivatives vanish. (d) Level diagram for two-qubit coupling, via either a nearest-neighbor electric-dipole interaction, or a long-distance photonic link in a microwave resonator. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img2_285765_mvMzV0po9N.jpg VII - Session VII: Ensemble donors and acceptors Oral presentation 075 Electron spin decoherence of J-coupled donor pairs in 2D delta-layers, 50 nm below surface in silicon M Tyryshkin1, S. A. Lyon1, E.S. Petersen1, A. J. Sigillito1, J. Jhaveri1, J. C. Sturm1, M. House2, M. Simmons2, C. C.

Lo3, J. J. L. Morton3 1Princeton University, PRINCETON, United States of America 2University of New South Wales, SYDNEY, Australia 3University College London, LONDON, United Kingdom To date, electron spin coherence studies of donors and exchange-coupled (J-coupled) donor pairs in silicon have been focused on bulk silicon crystals. Long coherence times have been demonstrated and the limiting spin decoherence mechanisms have now been well understood in bulk silicon. Here, we report the spin coherence measurements for 31P donors and J-coupled donor pairs in 2D δ-layers at 50 nm depth below silicon surface. The donors in the δ-layers are randomly “seeded”by exposing a Si [100] surface to a low dose of phosphene gas in an ultra-high vacuum environment. The 2D density of phosphorus atoms is estimated using scanning tunneling microscopy and a 50 nm thick capping silicon layer is then overgrown on top by solid source molecular beam epitaxy. In addition, the surface is passivated with 4 nm amorphous TiO2 layer formed by chemical deposition and low-temperature anneal. At donor densities of 2·1011 cm-2 in our δ-layers, only 25% of donors stay as isolated donors and all other donors form J-coupled pairs or higher-order clusters with a random distribution of J-couplings. We focus our coherence measurements on J-coupled donor pairs since their ESR signal sits separately from all other donor-related signals. The spin coherence times for J-coupled donor pairs in our δ-layers (T2 = 70-140 μs) are substantially shorter than 600 μs measured earlier for donor pairs in bulk natural silicon (4.7% of 29Si). The decoherence decays are non-exponential and show substantial dependence on magnetic field orientation. We find that the main decoherence mechanism for our J-coupled donor pairs in δ-layers is related to dangling-bond (Pb0) defects at the silicon surface 50 nm away. The decoherence mechanism is similar to a known instantaneous diffusion mechanism, however here the microwave pulses that excite the donor pair spins also excite the overlapping signal from the Pb0 spins. Overlapping of the J-coupled donor pair signal with the Pb0 signal depends on magnetic field orientation and this explains the observed orientation dependence in donor pair’s T2. 5 - Poster session Poster presentation 038 Atomically precise metrology of dopant positions in silicon M. Usman1, J. Bocquel2, J. Salfi2, B. Voisin2, A. Tankasala3, R. Rahman3, M.Y. Simmons2, S. Rogge2, L.C.L. Hollenberg4 1University of Melbourne, PARKVILLE, Australia 2CQC2T, School of Physics, University of New South Wales, SYDNEY, NSW, Australia 3Purdue University, WEST LAFAYETTE, United States of America 4CQC2T, School of Physics, University of Melbourne, PARKVILLE, VIC, Australia Shallow dopants in silicon are promising candidates for the implementation of spin qubits and quantum logic gates. Excellent progress in the last few years such as minutes-long coherence time [1], atomically precise fabrication technique [2], and surface code based architecture scheme [3] has brought silicon-donor based quantum computers much closer to reality. One of the key challenges in silicon based quantum computing is to find exact dopant positions after the fabrication and overgrowth processes, which would greatly help in the design and optimisation of highly precise quantum logic gates - a key ingredient for quantum error correction and scale up. Here we present an atomically precise metrology based on low temperature STM measurements [4] in conjunction with a fully quantum, large-volume treatment of the STM-dopant system [5], which demonstrates the pinpointing of the position of subsurface phosphorous (P) and arsenic (As) dopants in silicon down to individual lattice sites. The STM based metrology technique requires atomic scale understanding of the measured dopant images with quantitative precision. To solve this challenging problem, we establish a theoretical framework by coupling the Bardeen’s tunnelling theory [6] with the atomistic tight-binding simulations [7] of donor wave function in silicon, which reproduce the STM images of subsurface dopant wave functions with an unprecedented accuracy. Through systematic analysis of an exhaustive set of computed donor images, we discover unique patterns of image features, which are highly sensitive to the 3D positioning of the donor underneath the Si surface. Quantitative agreement between the measured and computed images provides a clear identification of the exact 3D location of both P and As donors in the Si lattice, down to depths of 5 nm below the Si surface [5]. The established exact donor position metrology will transform our knowledge of devices and dopant physics at the most fundamental scale leading to devices with optimised functionality, both in quantum and classical application. [1] K Saeedi et al., Science 342, 830, 2013 [2] B. Weber et al., Science 335, 64, 2012 [3] C. Hill et al., Science Adv. 1, e1500707, 2015

[4] J. Salfi et al., Nature Materials 13, 605, 2014 [5] M. Usman et al., arXiv:1601.02326, 2016 [6] J. Bardeen PRL 6, 57, 1966 [7] M. Usman et al., Phys. Rev. B. 91, 245209, 2015 Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286000_DJvErk3RZy.png Caption 1: Direct comparison of images from STM based measurements with large-scale theoretical calculations allows pinpointing the exact donor lattice location. 5 - Poster session Poster presentation 103 Electrical Detection of Impurity Orbital Transitions in Silicon Field Effect Transistors J Villis1, G Matmon1, P. T. Greenland1, Dong Li2, M Erfani1, Xiaomei Yu2, B. N. Murdin3, A. J. Fisher1, G Aeppli4 1UCL, LONDON, United Kingdom 2Peking University, BEIJING, China 3University of Surrey, GUILDFORD, United Kingdom 4ETH Zurich, VILLIGEN, Switzerland Excited orbitals have long been important for quantum science and technology, especially within trapped atoms and ions, used as qubit hosts. The analogue of such states exist in semiconductors including especially silicon, where they are the excited states of common impurities such as phosphorous [1,2]. They are addressable using free space optics, require no external magnetic fields for their definition, and perform functions such as the control of exchange interactions between electron spins on adjacent atoms [3]. Here we show how they can be excited optically and read out electrically as a function of gate voltage and temperature in a classic metal oxide field effect transistor (MOSFET), using Fourier transform infrared spectroscopy (FTIR). The gate-voltage-dependent switching characteristic of the current due to photoexcited orbitals between source and drain is step-like, in contrast to the linear onset for the switching of the ordinary current. This results from a reduction in the effective concentration of compensating impurities, at positive gate voltages, decreasing the rate pf electron recapture. The photocurrent has been characterised by a Fano Profile line shape with properties found to also to following a step-like gate dependence. Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_298733_n1tFpZ0XGu.jpg Caption 1: a) The gate-bias dependent photocurrent spectra of the MOSFET and b) the corresponding current-voltage curve. 5 - Poster session Poster presentation 030 Electrical addressing of donor systems in the STM B. Voisin1, J. Bocquel1, J. Salfi1, A. Tankasala2, M. Usman3, R. Rahman2, GK Klimeck2, BCJ Johnson3, JCM McCallum3, M.Y. Simmons1, L.C.L. Hollenberg3, S. Rogge1 1UNSW - CQC2T, KENSINGTON, Australia 2Purdue University, PURDUE, United States of America 3University of Melbourne - CQC2T, MELBOURNE, Australia Donors in silicon are robust spin qubits with a demonstrated potential for applications in quantum computation [1]. In this perspective, the control of interactions between donors in a complex environment is a key requirement. In the presented work, donor systems in silicon are electrically addressed using scanning tunneling microscopy and spectroscopy (STM/STS) [2], tools of choice to probe quantum systems properties at the atomic scale. P systems

have been fabricated at the nanoscale in UHV using CVD capabilities and STM lithography [3]. A vertical two-terminal architecture allows probing these donor systems within the single electron resonant tunneling regime [4]. We observe and map Coulomb blockade transitions in engineered quantum dots with a large number of electrons (N>20). Spatially resolved spectroscopy of donor pairs, with different donor-donor distances and orientations, shows excited states whose energies are compared to atomistic Full Configuration Interaction simulations. The independent tuning of donor levels at fixed bias requires the development of a third terminal. This has been implemented by implanting areas with donors, which act as metallic side electrodes, leading to an in-plane tunneling architecture. Isolated donors at the transition between doped and undoped regions are resolved and their associated resonance onset is shifted using the in-plane gate. Combining in-situ this three-terminal architecture, STM lithography and CVD growth enable probing and manipulating donor-based quantum states in STM. References [1] J. Muhonen et al., Nature Nanotechnology 9, 986-991 (2014) [2] J. Salfi et al., Nature Materials 13, 605-610 (2014) [3] M. Fuechsle et al., Nature Nanotechnology 7, 242-246 (2012) [4] B. Voisin et al., J. Phys.: Condens. Matter 27 154203 (2015) 5 - Poster session Poster presentation 067 Gate-defined quantum dot devices in undoped Si/SiGe heterostructures for spin qubit applications C Volk, F Martins, C M Marcus, F Kuemmeth Copenhagen University, KØBENHAVN, Denmark Spin qubits based on few electron quantum dots in semiconductor heterostructures are among the most promising systems for realizing quantum computation. Due to its low concentration of nuclear-spin-carrying isotopes, silicon is of special interest as a host material. We characterize gate-defined double and triple quantum dot devices fabricated from commercially available, undoped Si/Si$_{0.7}$Ge$_{0.3}$ heterostructures. Our device architecture is based on integrating all accumulation and depletion mode gates in a single gate layer. This simplifies device fabrication and allows local control of the confining potential without the need of a global accumulation gate. We present RF reflectometry techniques that allows fast read out of the quantum dot devices and recent progress towards implementing spin qubits in these structures. 5 - Poster session Poster presentation 003 Noise filtering of composite pulses in silicon quantum dot spin qubits XW WANG, XCY Yang City University of Hong Kong, KOWLOON, Hongkong Dynamically corrected gates are useful measures to combat decoherence in spin qubit systems. They are, however, mostly designed assuming the static-noise model and may thus be considered low-frequency noise filters. In this work we carefully examine the applicability of a particular type of dynamically corrected gates, namely the SUPCODE designed for singlet-triplet qubits, under realistic 1/fα noises. Through randomized benchmarking, we have found that supcode offers improvement of the gate fidelity for α>1 and the improvement becomes exponentially more pronounced with the increase of the noise exponent α up to 3. On the other hand, for small α supcode will not offer any improvement. We also present the computed filter transfer functions for the SUPCODE gates for nuclear and charge noise respectively and have found that they are consistent with the finding from the benchmarking. We discuss, in particular, its consequence on silicon-based quantum dot spin qubits.

II - Session II: Single donors and acceptors Oral presentation 077 Coherent control of two electron spin qubits bound to Si/SiGe quantum dots T. F. Watson1, E. Kawakami1, P Scarlino1, D. R. Ward2, D. E. Savage2, M. G. Lagally2, M. Friesen2, S. N. Coppersmith2, M. A. Eriksson2, L. M. K. Vandersypen1 1Delft University of Technology, DELFT, The Netherlands 2University of Wisconsin-Madison, MADISON, United States of America Recently, we have shown the all-electrical coherent control of a single electron spin with a gate fidelity of ~99% by electron dipole spin resonance in a magnetic field gradient [1,2]. The next step is to exchange couple two electron spin qubits and to perform a two-qubit gate using the difference in the Zeeman energy of the two electron spins generated using micromagnets [3,4]. Here, we demonstrate the independent readout and coherent control of two coupled electron spins with resonance frequencies separated by ~1GHz. We perform ESR spectroscopy of the two spin qubits as a function of the detuning energy showing clear evidence of exchange coupling. We report on recent progress in implementing a two qubit gate in this system. [1] E. Kawakami et al., Nature Nanotechnology 9, 666 (2014) [2] E. Kawakami et al., arXiv:1602.08334 (2016) [3] T. Meunier et al., Physical Review B 83, 121403 (2011) [4] M. Veldhorst et al., Nature 526, 410 (2015) IV - Session IV: Quantum dots and nanowires Oral presentation 020 Heavy-hole charge sensing and double quantum dots in Ge hut-wires HW Watzinger1, LV Vukušic2, JK Kukucka2, EL Lausecker2, AT Truhlar2, RK Kirchschlager2, VS Sessi3, MG Glaser1, FS Schäffler1, GK Katsaros2 1Johannes Kepler University, LINZ, Austria 2IST Austria, KLOSTERNEUBURG, Austria 3NaMLab gGmbH, DRESDEN, Germany Holes confined in group IV quantum dots are a promising option for the realization of spin qubits. Although studied much less than electrons [1], holes have as well long spin lifetimes and dephasing times [2]. In addition, due to their strong spin orbit coupling, they can be electrically manipulated. In our group we study holes which are confined in SiGe self-assembled nanostructures [3], realized by direct growth of Ge on Si substrates via the Stranski-Krastanow growth mode. Here we focus on transport measurements through so called Ge hut-wires (HWs) [4], nanostructures with well-defined surfaces and growth orientations, with heights of about 2 nm and lengths exceeding one micrometer. The obtained g-factors show a high in-plane and out-of-plane anisotropy which indicates the nature of the hole states to be heavy hole like [5]; such is important for achieving long spin coherence times. In order to move towards experiments determining the relaxation and coherence times charge sensors and double quantum dot devices are needed. The former has been realized by coupling two HWs, not only electrostatically, but also via tunneling, opening the way to efficient spin to charge conversion and spin readout [6]. By adding a thin barrier gate to the middle of a HW, a double dot can be realized, opening thus also the path for the study of 2-hole qubits. This work is supported by the EC FP7 ICT project no. 323841 and the ERC Starting Grant no. 335497. [1] Morello, A. et al., Nature 467, 687-691 (2010); Maune, B. M. et al., Nature 481, 344-347 (2012); Büch, H. et al., Nature Comm. 4 (2013); Simmons, C. B. et al., Phys. Rev. Lett. 106, 156804 (2011); Zwanenburg, F. A., Rev. Mod. Phys. 85, 961 (2013) [2] Y. Hu et al., Nature Nanotechnology 2, 622 (2007); Y. Hu et al., Nature Nanotechnology 7, 47-50 (2012) ; A. P. Higginbotham et al., Nano Letters 14, 3582 (2014) [3] Katsaros, G. et al., Nature Nanotechnology 5, 458-464 (2010); Katsaros, G. et al. , Phys. Rev. Lett. 107, 246601 (2011);

Ares, N. et. al., Phys. Rev. Lett. 110, 046602 (2013) [4] Zhang, J. J. et al., Phys. Rev. Lett. 109, 085502 (2012); Watzinger, H. et al., APL Mater. 2, 076102 (2014) [5] Watzinger, H. et al. (in preparation) [6] Vukušić, L. et al. (unpublished) Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_285964_B7lCJkhJgz.jpg Caption 1: Schematic of a HW double dot device. 5 - Poster session Poster presentation 023 Circuitry built of Silicon atom quantum dots RA Wolkow University of Alberta, EDMONTON, Canada Individual silicon dangling bonds on an otherwise H-terminated silicon surface can serve as quantum dots and as classical computing elements such as the building blocks of room temperature quantum cellular automata [1]. Small ensembles of atomic silicon quantum dots, ASiQDs, have been examined as qubits [2,3]. Indeed, by patterning ASiQDs appropriately, all the components required to create circuitry, from passive elements such as analog wires to active components such as switches can we suspect, be built [4]. New insights into the nature of the connection between bulk silicon and single surface silicon atoms will be described. It will be shown that current voltage spectroscopy are not a simple reflection of local simple density of states and that single electron charge state changes dominate observed spectra [5]. The first application of all electrical scanning tunneling microscopy pump probe techniques has resulted in nanosecond resolved single dopant charge dynamics in silicon [6]. State of the art bond-resolving non-contact qplus atomic force microscopy has been applied for the first time to create detailed images of the H-terminated silicon surface at forces spanning the attractive to the hard repulsive regimes, opening the door to an imaging and fabricating approach that is at least complimentary to, and perhaps could supplant STM in silicon atom scale studies [7]. [1] PRL 102, 046805 (2009) [2] NJP 12, 083018 (2010) [3] PRB 89, 035315 (2014) [4] Lecture notes in computer science: Field-Coupled Nanocomputing ed. N G Anderson and S Bhanja (Berlin: Springer) pp 33-58, (2014) [5] NJP 17, 073023 (2015) [6] arXiv:1512.01101 [7] preprint available at conference time, hopefully 5 - Poster session Poster presentation 041 Magnetic field dependence of Pauli spin blockade in p-channel silicon double quantum dots Y.Y. Yamaoka, K.I. mr. Iwasaki, S.O. prof. Oda, T.S. prof. Kodera Tokyo Institute of Technology, TOKYO, Japan P-channel Si DQDs are studied well recently [1,2], since holes in Si QDs have a wave function with p-like orbital, leading to reduction of hyperfine interaction with surrounding nuclear spins. Therefore, the coherent time of hole spins is expected to be longer than that of electron spins. In this work, we successfully observed magnetic field dependence of Pauli spin blockade in p-channel Si DQDs. We observed both a dip of leakage current at zero field possibly due to the spin-orbit interaction induced spin relaxation and a peak possibly due to spin-flip cotunneling [2].

We found the magnetic field dependence of the leakage current depends on the top gate (TG) voltages. We fabricated physically defined DQDs with capacitive coupled single hole transistor for charge sensing on silicon-on-insulator substrate (Fig.1). Fig.2 (a) shows the charge triple point and Pauli spin blockade measured at 4.2 K. Fig. 2 (b) and (c) show magnetic field dependences of leakage current in Pauli spin blockade at the TG voltages of -2.4 V and -2.5 V, respectively. Leakage current in Fig. 2 (b) has mixed-like characteristics between a dip and a peak. By applying more negative TG voltage, the peak-only characteristics were obtained (Fig. 2 (c)). This indicates that the TG can control spin-orbit interaction and provides a pathway toward hole spin Qubits. Part of this work is financially supported by Kakenhi Grants-in-Aid (Nos. 26709023, 26630151, and 26249048), and the Project for Developing Innovation Systems of the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan [1] Voisin., et al., Nano Lett., 2016, 16 (1), pp 88-92 [2] Ruoyu Li., et al., Nano Lett., 2015, 15 (11), pp 7314-7318 Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img2_286009_pZZSfTUoeO.png Caption 1: Fig. 2. Charge triple point and the Magnetic field dependences of the leakage current in Pauli spin blockade. Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img1_286009_pZZSfTUoeO.png Caption 2: Fig. 1. SEM image of the p-channel DQD device. 200 nm-thick poly-Si top gate is formed on the device. 5 - Poster session Poster presentation 034 Effect of Valleys and Parasitic Spin on a Quantum Dot Qubit C. H. Yang1, J. C. C. Hwang1, M. A. Fogarty1, W. Huang1, N. Hendrickx2, M. Veldhorst1, A. S. Dzurak1 1UNSW Australia, SYDNEY, Australia 2University of Twente, ENSCHEDE, The Netherlands Spin qubits in silicon quantum dots have shown great progress in recent years with the demonstrations of single qubit gates [1-3] as well as two qubit logic operations [4]. In this work, we map out the electron spin resonance (ESR) spectrum of a single spin qubit defined in a silicon MOS quantum dot system. By extracting the Stark shift for the resonance frequencies of the qubit, we find that the voltages on the two dot plunger gates contribute g-factor changes with opposing sign. We also observe multiple resonance branches for the same spin, when we couple it to the second spin qubit. To fit the data we consider a mathematical model that contains anti-crossings between at least three vertical and five horizontal resonance branches. We examine the possible origins of these multiple resonance branches by considering factors such as valley-state crossings or coupling to spins in unintentional dots. [1] M. Maune et al., Nature 481, 344-347 (2012). [2] Veldhorst et al., Nature Nanotechnology 9, 981-985 (2014). [3] Kawakami et al., Nature Nanotechnology 9, 666 (2014). [4] Veldhorst et al., Nature 526, 410-414 (2015). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img2_285991_HpBVebpWS4.png Caption 1: Multi-level anti-crossing in ESR spectrum. Picture 2: https://www.eventure-online.com/parthen-uploads/19/880/img1_285991_HpBVebpWS4.png Caption 2: Stark shift in ESR frequency from gates G1, G2. V - Session V: Quantum dot qubits

Oral presentation 009 Achieving high fidelity single qubit gates of a silicon quantum dot hybrid qubit using strong driving Y. Y. Yang, S. N. C. professor Coppersmith, M. F. Friesen University of Wisconsin-Madison, MADISON, WI, United States of America Performing qubit gate operations as quickly as possible minimizes the effects of decoherence. For resonant gates, this requires applying a strong ac drive. However, strong driving can present control challenges by causing leakage to electronic levels that lie outside the qubit subspace. Strong driving can also present theoretical challenges, because preferred tools such as the rotating wave approximation can break down, resulting in complex dynamics that are difficult to control. Here we analyze a resonant X gate of a silicon quantum double dot hybrid qubit within a dressed-state formalism, obtaining results beyond the rotating wave approximation. We obtain analytic formulas for the optimum driving frequency and the Rabi frequency, which both are affected by strong driving. While the qubit states exhibit fast oscillations due to counter-rotating terms and leakage, we show that they can be suppressed to the point that gate fidelities above 99.99% are possible, in the absence of charge noise. Hence, decoherence mechanisms, rather than strong-driving effects, should represent the limiting factor for X-gate fidelities in a quantum dot hybrid qubit. 5 - Poster session Poster presentation 043 Crystal field splitting of a single erbium ion in silicon C Yin1, Q Zhang1, G G De Boo1, M Rancic2, B C Johnson3, J C McCallum3, M J Sellars2, S Rogge1 1The University of New South Wales, UNSW, Australia 2Australian National University, CANBERRA, Australia 3University of Melbourne, MELBOURNE, Australia Optical access to single spins in silicon has the potential for scalable quantum computing by coupling distant single spins using silicon-based optical cavities. As one initial step, an optical/electrical hybrid approach has been shown to address the electron and nuclear spins of a single erbium ion in a silicon nano-transistor [1]. Long coherence time of rare earth ions has been demonstrated with europium ions in Y2SiO5 [2], and the site symmetry of the rare earth ion and magnetic field orientation are both key points for extending the nuclear spin relaxation time and coherence time [3]. In this work, we study the crystal field splitting and field rotation dependence of a single erbium ion in a silicon nano-transistor. Different crystal field levels are measured under different magnetic field, and show strong level repulsion as increasing the magnetic field. Together with a theoretical simulation of the spin Hamiltonian, we aim to optimize the nuclear spin relaxation time in our experiments. [1] C. Yin, M. Rancic, G. G. de Boo, N. Stavrias, J. C. McCallum, M. J. Sellars, & S. Rogge. Optical addressing of an individual erbium ion in silicon., Nature 497, 91 (2013). [2] M. Zhong, M. P. Hedges, R. L. Ahlefeldt, J. G. Bartholomew, S. E. Beavan, S. M. Wittig, J. J. Longdell & Matthew J. Sellars. Optically addressable nuclear spins in a solid with a six-hour coherence time. Nature 517, 177 (2015). [3] J. G. Bartholomew, R. L. Ahlefeldt, & M. J. Sellars, Phys. Rev. B 93, 014401 (2016). 5 - Poster session Poster presentation 050 Multiplexed reflectometry measurement of a gate-defined Si-MOS quantum dot J Yoneda1, T. Honda2, K. Takeda1, M. Marx1, T. Otsuka1, T. Nakajima1, M. R. Delbecq1, S. Amaha1, G. Allison1, T. Kodera2, S. Oda2, S. Tarucha1 1RIKEN, SAITAMA, Japan 2Tokyo Institute of Technology, TOKYO, Japan

Recent progress in Si quantum spintronics in quantum dots (QDs) calls for simultaneous, wide-bandwidth detection of electron occupancies in QDs. This is particularly desirable for QD-spin-based quantum computation to read out multiple qubit spin states within their coherence times. A promising method to achieve high measurement bandwidth is the radio-frequency (rf) reflectometry [1]. Furthermore, the technique can be frequency multiplexed so that different sensors associated to different spins can be measured simultaneously at different frequencies. In this presentation, we will report on the rf-reflectometry measurement at different frequencies of two neighbouring channels integrated in a Si-MOS QD device. We found that, depending on the inducing gate geometry, the resonance frequency can be heavily gate-voltage dependent. While this might be useful to tune the resonance in situ, it will result in crosstalk for multiplexed rf readout. To separate resonance frequencies in individual sensor channels, one needs a precise determination of the parasitic capacitance of the channel seen by the injected rf. To realize this, we confirmed experimentally that when the inducing gate is properly designed to minimize the induced capacitance beneath, the gate-voltage-induced shift in the resonance frequency becomes negligible, within the tank circuit resonance width. In such a case, we observed Coulomb diamonds in the amplitude and the phase response by demodulating the reflected rf at an expected, constant frequency. [1] S. J. Angus et al., Appl. Phys. Lett. 92, 112103 (2008). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286029_MX695qEAZZ.png 5 - Poster session Poster presentation 062 Validation of a silicon single-electron pump with traceability to primary standards RZ Zhao1, AR dr. Rossi2, SPG dr. Giblin3, MK dr. Kataoka3, JF dr. Fletcher3, FH dr. Fay1, MM dr. Möttönen4, ASD prof. Dzurak1 1University of New South Wales, SYDNEY, Australia 2Cavendish Laboratory, University of Cambridge, CAMBRIDGE, United Kingdom 3National Physical Laboratory, TEDDINGTON, United Kingdom 4QCD Labs, Department of Applied Physics, Aalto University, AALTO, Finland Validation of a silicon single-electron pump with traceability to primary standards Ruichen Zhao1, Alessandro Rossi2, Stephen Giblin3, Masaya Kataoka3, Jonathan Fletcher3, Fay E. Hudson1, Mikko Möttönen4, Andrew Dzurak1. School of Electrical Engineering & Telecommunications, University of New South Wales, Sydney NSW 2052, Australia. Cavendish Laboratory, University of Cambridge, J.J. Thomson Ave CB3 0HE, Cambridge, UK National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom. QCD Labs, Department of Applied Physics, Aalto University, 00076 Aalto, Finland. Keywords: single-electron pump, electrical current standard, dynamic quantum dot. Single-electron pumps based on planar silicon metal-oxide-semiconductor (MOS) quantum dots have the potential to generate highly accurate electric currents [1]. Indeed, by periodically driving one of the barrier gates, one electron per cycle can be captured from the source and ejected into the drain at GHz frequencies (Fig1). Furthermore, by controlling the quantum dot`s electrostatic potential through purposely engineered confinement gates, one can greatly reduce capture errors [2]. As such, silicon-based implementations are advantageous since the device operation is much less demanding with respect to other competing technologies, which may require high magnetic field or tailored waveforms to achieve good performances [3]. Silicon pumps could provide a pathway to implement a new quantum-based standard of electric current, as well as leading to the realization of precise on-demand electron sources in the context of scalable quantum computing. In this work, we experimentally determine the accuracy of a silicon pump by comparing its output current to a reference source that can be linked to the primary metrology standards of voltage and resistance via the ac Josephson effect and the quantum hall effect, respectively. The device was fabricated on an intrinsic silicon substrate with an 8nm-thick high quality thermal silicon dioxide. On top of it, there are 3 layers of lithographically defined gate electrodes that are electrically insulated from each other by thermally grown aluminum oxide. This gate arrangement allows one to electrostatically define a few-electron quantum dot at the Si/SiO2 interface (Fig1). By driving one of the gates with a single harmonic oscillator, we modulate the transparency of the dot’s input tunnel

barrier. This results in the generation of a quantized output current with part-per-million accuracy and electron transfers as fast as nanosecond timescales. In addition, we observe that for some operation points, quantum spillage of captured electrons results in a deterioration in the current quantization. We show that the precise control over the quantum dot energy landscape typical of our device design, is the key to attain high-speed electron transfer with ultra-low error rates. Pekola, J. P., et al. Rev. Mod. Phys. 85, 1421-1472 (2013). Rossi, A., et al. Nano Letters 14, 3405 (2014). Giblin, S. P., et al. Nat. Comm., 3, 930 (2012). Picture 1: https://www.eventure-online.com/parthen-uploads/19/880/img1_286057_xjnYHaxoJT.png Caption 1: SEM image of the silicon single electron pump IV - Session IV: Quantum dots and nanowires Oral presentation 087 Are quantum dots in unexpected locations due to strain? N Zimmerman1, T Thorbeck2 , GAITH, United States of America 2UWM, MADISON, United States of America It is a fairly common occurrence that, in top-gated Si quantum dots, the dots appear in reproducible but unexpected positions. For instance, sometimes a group will make gates in order to electrostatically generate tunnel barriers, but discover that the quantum dot is formed underneath the gate rather than between two barrier gates. We will discuss the possibility that such quantum dots arise from the mechanical strain induced by the gate. The model is simple: i) We simulate metal or polysilicon gates on top of a Si/SiO2 wafer, and calculate the stress and strain from differential thermal contraction of the materials; ii) Using the fact that the energy of the Si conduction band depends on strain through the deformation potential, we then convert the strain modulation to a potential energy modulation. As an example, we find that, for a single Al gate, there is a potential well directly underneath the gate with the size of a few meV, in agreement with recent experimental results. Finally, time permitting, we will speculate on the possibility of using this strain-induced effect as an advantage, perhaps by generating quantum dots that both/either i) are closer together and/or ii) require fewer gates to generate and control. 5 - Poster session Poster presentation 036 Test test silicon bravo FA Zwanenburg , DELFT, The Netherlands Antilles wordt een mooi feestje