Frontiers of Matter Wave Optics · Laboratoire Charles Fabry de l'Institut d'Optique, Campus...

Frontiers of Matter Wave Optics

Obergurgl, March 20-26

Book of Abstracts

Organizing Committee:Hanns-Christoph Nagerl

Markus ArndtErnst M. Rasel

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Table Of Contents - Talks

J. Arlt Page 1Pump-probe spectroscopy in an optical latticeP. Berg Page 2

Matter waves for rotation sensingP. Bouyer Page 3

Quantum transport with matter-wavesD. Cassettari

Novel Optical Traps for Ultracold AtomsM. Cheneau Page 5

Single-site-resolved detection and manipulation of atoms in an optical latticeS. L. Cornish Page 6

A Quantum Degenerate Mixture of 87Rb and 133CsS. Eibenberger Page 7

Matter wave interference with complex moleculesN. Gaaloul Page 8

Interferometry with Bose-Einstein Condensates in microgravityS. Gardiner Page 9

Bright Matter-Wave Soliton Collisions with Controlled Relative PhaseS. Guellati-Khelifa Page 10

New determination of the fine structure constant and test of the quantum elec-trodynamicE. Haller Page 11

Three-body loss and three-body correlations in one-dimensional systemsP. Haslinger Page 12

Setting up an all optical time domain Talbot-Lau Interferometer for large metalclustersM. Hauth Page 13

GAIN — a high-precision mobile gravimeter based on atom interferometryA. Hemmerich Page 14

Coherence and chiral order in higher bands of an optical latticeS. Jochim Page 15

A tunable few-fermion systemM. Kasevich Page 16

Quantum metrology with cold atomsC. Klempt Page 17

Pair correlated matter waves for quantum interferometryA. Landragin Page 18

Cold Atom Interferometers for inertial measurementsA. Lazarides Page 19

Strongly interacting bosons in a 1D optical lattice at incommensurate densitiesC. Lisdat Page 20

The Strontium Optical Lattice Clock at PTBG. Modugno Page 21

Exploring the physics of disorder with a tunable Bose-Einstein condensateO. Morsch Page 22

Coherent control of dressed matter waves in strongly driven periodic potentials

iii

M. Oberthaler Page 23Quantum Atom Optics: Spin squeezed states and atomic two-mode squeezedvacuumD. Poletti Page 24

Cold atoms in a 1D periodically driven systemH. Ritsch Page 25

Cavity QED with ultracold gasesP. Rosenbusch Page 26

Spin self-rephasing and very long coherence timesG. Rosi Page 27

The MAGIA experiment: status and prospectsC. Salomon Page 29

Clocks, atom interferometers and tests of the gravitational redshiftL. Santos Page 30

Spinor gases in optical latticesJ. Schmiedmayer Page 31

Probing non equilibrium physics in 1d quantum many body quantum systemsby interferenceT. Schumm Page 32

A down-conversion source for twin-atom beamsS. Slama Page 33

Plasmonic nanopotentials for cold atomsA. Smerzi Page 34

Multiparticle Entanglement for Quantum InterferometryJ. K. Thompson Page 35

Conditional Spin-Squeezing of a Large Ensemble via the Vacuum Rabi SplittingM. Trippenbach Page 36

Mean field effects on the scattered atoms in condensate collisionsH. Ulbricht Page 37

Molecule interferometryW. v. Klitzing Page 38

Ultra-sensitive atom imaging for matter-wave interferometryS. Will Page 39

Time-Resolved Observation of Coherent Multi-Body Interactions in QuantumPhase RevivalsB. S. Zhao Page 40

Quantum Reflection of He2 Several Nanometers Above a Grating SurfaceW. H. Zurek Page 41

Causality in Condensates

iv

Table Of Contents - Posters

B. Allard Page 42Anisotropic 2D diffusive expansion of ultra-cold atoms in a disordered potentialC. Basler Page 43

A study of CPT resonances in an optical dipole trapT. Betz Page 44

Two-point phase correlations of a one-dimensional bosonic Josephson junctionU. Bissbort Page 45

Detecting the amplitude mode by Bragg spectroscopy in strongly correlated lat-tice bosonsM. Bruvelis Page 46

Interference patterns of laser-dressed states in a supersonic atomic/molecularbeamM. Buchhold Page 47

Creating exotic condensates through the interplay of quantum phase revival andtrap dynamicsJ. P. Chwedenczuk Page 48

Phase estimation with interfering Bose-Einstein-condensed atomic cloudsJ. Cotter Page 49

Measuring Energy Differences by BEC Interferometry on a ChipJ. Dunningham Page 50

Metrology with rotating matter wavesD. Efimov Page 51

Penning ionization of two ultracold Rydberg atomsW. Ertmer Page 52

Giant coherence time due to spin self-rephasing in an optical trapM. Gildemeister Page 53

A ring trap for matter-wave interferometryT. Griesser Page 54

Multispecies kinetic theory of cavity-mediated cooling and selforganisationS. Handel Page 55

Bright matter wave solitons: Formation, dynamics and quantum reflectionT. Hartmann Page 56

Weak (anti-)localization of Bose-Einstein condensates in two-dimensionalchaotic cavitiesK. Hippalgaonkar Page 57

Correlated phonon scattering in mesoscopic Silicon NanowiresA. Joyet Page 58

Continuous approach to cold atom interferometersN. S. Kampel Page 59

Blue/Red Superradiance Threshold AsymmetryY. H. Lien 0

Study of systematic effects for Newtonian gravitation constant measurement inMAGIA experimentN. Lo Gullo Page 61

Vortex patterns’ structural changesF. Meinert Page 62

A study of CPT resonances in an optical dipole trap

v

J. Michl Page 63Interaction-based reduction of weak localization in coherent transport of Bose-Einstein CondensatesW. Niedenzu Page 64

Microscopic dynamics of ultracold particles in a ring-cavity optical latticeL. Pezze Page 65

Localized and Extended states in a disordered trapM. Rabie Page 66

Three-body correlation function and recombination rate in one-dimensional sys-temsL. Reichsollner Page 67

Design of a high-power frequency-doubled laser system for an optical superlatticefor ultracold cesium atomsM. F. Riedel Page 68

Atom chip based generation of entanglement for quantum metrologyB. Sherlock Page 69

A ring trap for matter-wave interferometryY. Singh 0

Strontium in an Optical Lattice as a Mobile Frequency ReferenceP. Thomann Page 71

Continuous approach to cold atom interferometersJ. Wernsdorfer Page 72

Strongly Correlated Ultracold Fermions in Disordered Optical Lattices

vi

Pump-probe spectroscopy in an optical lattice

Jacob F. Sherson,1 Sung Jong Park,1 Sune Mai,1 Poul Pedersen,1 Nils Winter,1 and Jan Arlt1, ∗

1Danish National Research Foundation Center for Quantum Optics,Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark

Time resolved pump-probe spectroscopy is a universal tool of importance in fields ranging from molecular to solidstate physics. Starting from a bound state, a short pump pulse is used to create a coherent superposition or wavepacket in an excited state. In a second step the probe pulse interrogates the dynamic evolution of this wave packetby transferring it to another bound state. This process can thus provide information about coherent dynamics inthe excited state, but it can equally well be used for precision spectroscopy of for the preparation of a desired final state.

We show that a similar process can be realized in an optical lattice by using modulation spectroscopy. A short burstof amplitude modulation can induce two-step transitions to states above the lattice threshold. Thus quasi-free wavepackets only bound by the external harmonic confinement are produced. A second burst of modulation then allowsus to monitor and deexcite the wave packet in a pump-probe fashion. The process also allows for the production ofwell localized states in the lattice outside the BEC region that may lend themselves to precision measurements. Allsteps of this process are monitored in situ and all affiliated time scales can be resolved.

∗Electronic address: [email protected]; URL: http://phys.au.dk/forskning/uqgg/

1

Matter waves for rotation sensing

P. Berg,1, ∗ S. Abend,1 Ch. Schubert,1 G. Tackmann,1 M. Gilowski,1 W. Ertmer,1 and E. M. Rasel1

1Institut fur Quantenoptik, Universitat HannoverWelfengarten 1, 30167 Hannover, Germany

Tel +49 0511 762-4107, Fax +49 0511 762-2211

In this talk we introduce the research project CASI (Cold Atom Sagnac Interferometer) which is intended toexplore the potential of mater wave interferometry in the context of rotation sensing. The experiment is based oncold 87Rb-atoms which are launched onto a parabolic trajectory in a pulsed mode with a longitudinal velocity of 2.79m/s. During the flight the atoms pass transversally oriented velocity selective Raman beam splitters thus providingthe possibility to span up different inteferometer goemetries in the horizontal plane. The detection scheme employsstate selective flourenscence measurement. In order to suppress vibrational noise the interferometer is operated ina differential manner utilizing two counterpropagating atomic wave packets. With the current setup a short termsensitivity of 2 · 10−6 rad/s and an integration time of about 300 s for rotation measurements has been reached.

We focus on the successful realisation of a spatially separated three-pulse interferometer geometry with signalcontrast of about 20% and a total interogation time of 2T = 49 ms corresponding to an area of 16 mm2. Thistheoretically enables us to perform a shot-noise limited rotation sensitivity of the order of 10−8 rad/s at a detectedatom number of a few 106. Because relative beam splitter wave front tilts lead to a loss of contrast the light fields haveto be carefully aligned with respect ot each other within an acceptance angle of 10 µrad. The necessary alignmentprocedure will be discussed as well as further improvements of the current interferometer sensitivity including thereduction of background noise.

This work is supported by the DFG, QUEST, and IQS.

∗Electronic address: [email protected]; URL: http://www.iqo.uni-hannover.de

2

Quantum transport with matter-waves

Philippe BouyerLaboratoire Charles Fabry de l’Institut d’Optique, Campus Polytechnique,

rd 128, 91127 PALAISEAU CEDEX, France andPhysics Dpt, Stanford University, CA 94305-4060, Stanford, USA

FIG. 1. Observation of Anderson localization in 1D with anexpanding Bose-Einstein Condensate in the presence of a 1Dspeckle disorder.

The transport of quantum particles in non ideal mate-

rial media (eg the conduction of electrons in an imperfect

crystal) is strongly affected by scattering from impurities

of the medium. Even for a weak disorder, semi-classical

theories, such as those based on the Boltzmann equation

for matter-waves scattering from the impurities, often

fail to describe transport properties and full quantum

approaches are necessary. The properties of the quan-

tum systems are of fundamental interest as they show

intriguing and non-intuitive phenomena that are not yet

fully understood such as Anderson localization, percola-

tion, disorder-driven quantum phase transitions and the

corresponding Bose-glass or spin-glass phases. Under-

standing quantum transport in amorphous solids is one

of the main issues in this context, related to electric and

thermal conductivities.

Ultracold atomic gases can now be considered to re-

visit the problem of quantum conductivity and quan-

tum transport under unique control possibilities. Dilute

atomic Bose-Einstein condensates (BEC) and degener-

ate Fermi gases (DFG) are produced routinely taking

advantage of the recent progress in cooling and trap-

ping of neutral atoms. Transport has been widely in-vestigated in controlled potentials with no defects, for

instance periodic potentials (optical lattices). Controlled

disordered potentials can also be produced with various

techniques such as the use of magnetic traps designed

on atomic chips with rough wires, the use of localized

impurity atoms, the use of radio-frequency fields or the

use of optical potentials. This recently lead to the ob-

servation of the Anderson Localisation of a BEC and the

measurement of the diffusion coefficient of a 2D gaz in

the presence of disorder. I will also discuss the recent

development towards the observation of AL in 3D with

matter-waves.

3

Novel Optical Traps for Ultracold Atoms

Graham D. Bruce,1 James Mayoh,1 Lara Torralbo Campo,1 Giuseppe Smirne,1 and Donatella Cassettari1

1SUPA, School of Physics and Astronomy, University of St Andrews,North Haugh, St Andrews, KY16 9SS, United Kingdom

The use of a Spatial Light Modulator (SLM) to generate optical traps for ultracold atoms opens the possibilityof forming non-periodic and non-trivial patterns of dipole traps to create trapping geometries not achievable usingexisting techniques. The SLM is an inherently dynamic tool that offers the opportunity to generate smooth, time-varying optical potentials that can in principle be employed to achieve full coherent control over the trapped gas. Weoutline the work in progress at St Andrews to achieve novel trapping geometries for ultracold atoms using an SLM.

[1] Smooth, holographically generated ring trap for the investigation of superfluidity in ultracold atoms, G D Bruce et al, arXiv:1008.2140

4

Single-site-resolved detection and manipulation of atoms in an optical lattice

M. Cheneau,1, ∗ C. Weiteberg,1 M. Endres,1 J. Sherson,1 P. Schauß,1 T. Fukuhara,1 I. Bloch,1 and S. Kuhr1

1Max-Planck-Institut fur QuantenoptikHans-Kopfermann-Straße 1, D-85748 Garching, Germany

The reliable detection and coherent manipulation of single quantum particles has revolutionized the field of quantumoptics and opened the way to quantum information processing. For several years, a lot of effort has been devotedto the extension of such capabilities to larger-scale, many-body systems in optical lattices. Here we report on twodecisive steps we recently made towards this goal.

In a first series of experiements [1], we recorded fluorescence images of a bosonic Mott insulator allowing to re-construct the atom distribution on the lattice and identify individual excitations with high fidelity. A comparisonof the radial density and variance distributions with theory provided a precise in-situ temperature and entropy mea-surement from single images. We observed Mott-insulating plateaus with near-zero entropy and clearly resolved thehigh-entropy rings separating them, even though their width is of the order of just a single lattice site. Furthermore,we showed how a Mott insulator melts with increasing temperature, owing to the proliferation of local defects.

In a second series of experiment [2], using a tightly focussed laser beam together with a microwave field, we wereable to flip the spin of individual atoms in the Mott insulator with sub-diffraction-limited resolution, well below thelattice spacing. The Mott insulator provided us with a large two-dimensional array of perfectly arranged atoms, inwhich we created arbitrary spin patterns by sequentially addressing selected lattice sites after freezing out the atomdistribution (Fig. 1). We directly monitored the tunneling quantum dynamics of single atoms in the lattice preparedalong a single line and observed that our addressing scheme leaves the atoms in the motional ground state.

These results open the path to a wide range of novel applications from quantum dynamics of spin impurities, entropytransport, implementation of novel cooling schemes, and engineering of quantum many-body phases to quantuminformation processing.

a

2 µm

b

x

y

FIG. 1: a, Experimentally obtained fluorescence image of a Mott insulator with unity filling in which the spin of selected atomswas flipped from |0〉 to |1〉 using our single-site addressing scheme. |1〉 were removed by a resonant laser pulse before detection.The lower part shows the reconstructed atom number distribution on the lattice. Each circle indicates a single atom, the pointsmark the lattice sites. b, Same as a, but a global microwave sweep exchanged the population in|0〉 to |1〉, such that only theaddressed atoms were observed.

[1] Single-atom resolved fluorescence imaging of an atomic Mott insulator, J. F. Sherson, C. Weitenberg, M. Endres, M. Cheneau,I. Bloch and S. Kuhr, Nature 467 (2010).

[2] Single-Spin Addressing in an Atomic Mott Insulator, C. Weitenberg, M. Endres, J. F. Sherson, M. Cheneau, Peter Schauß,Takeshi Fukuhara, I. Bloch and S. Kuhr, arXiv 1101.2076v1 (2011), to be published in Nature.

∗Electronic address: [email protected]

5

A Quantum Degenerate Mixture of 87Rb and 133Cs

S. L. Cornish,1, ∗ D. J. McCarron,1 D. L. Jenkin,1 M. P. Koppinger,1 and H. W. Cho1

1Department of Physics, Durham University, South Road, Durham DH1 3LE, UK.Tel +44(0)191-3343574, Fax +44 (0)191-3345823

Quantum degenerate mixtures of two or more atomic species open up many new research avenues, including theformation of ultracold heteronuclear molecules [1]. Such molecules possess permanent electric dipole moments whichgive rise to anisotropic, long range dipole-dipole interactions. These interactions differ greatly from the isotropic,short-range contact interaction commonly encountered in quantum degenerate atomic gases and consequently offernovel applications in quantum information processing [2] and simulation [3]. Recently, great successes have beenachieved in the creation of high phase space density molecular gases by combining magneto-association on a Feshbachresonance with stimulated Raman adiabatic passage (STIRAP) to transfer the molecules to the ro-vibrational groundstate [4–6]. The pre-requisite to this approach is the attainment of a high phase space density atomic mixture. Herewe present the realisation of a quantum degenerate mixture of 87Rb and 133Cs following a novel approach in whichthe 133Cs gas is sympathetically cooled. Initially ∼ 4 × 108 87Rb atoms and ∼ 2 × 107 133Cs atoms are collectedin an ultra high vacuum magneto-optical trap (MOT) and transferred into a magnetic quadrupole trap. Forced RFevaporation is used to cool the 87Rb atoms, while interspecies elastic collisions ensure that the 133Cs atoms are cooledsympathetically. This cooling is ceased once the Majorana losses become significant. The mixture is then transferredinto an optical dipole trap formed at the intersection of two crossed laser beams by simply ramping down the gradientof the quadrupole trap to ∼ 30 Gcm−1. The atoms are subsequently transferred to their absolute internal groundstates. By reducing the depth of the dipole trap further evaporation and sympathetic cooling allow us to producetwo species Bose-Einstein condensates containing ∼ 2 × 104 atoms of each species. Preliminary observations of thedegenerate mixture reveal immiscible behavior via a dramatic spatial separation of the two species. Altering the initialcomposition of the mixture allows the production of pure single species 133Cs condensates of up to 6 × 104 atoms.

87Rb 133Cs

(b)(a)

FIG. 1: (a) The observation of Bose-Einstein condensation in a gas of 133Cs atoms as the system is cooled below the transitiontemperature. (b) The observation of phase separation in a quantum degenerate mixture of 87Rb and 133Cs.

[1] Cold and ultracold molecules: science, technology and applications, L.D. Carr, D. DeMille, R.V. Krems, J. Ye, New J. Phys.11(5), 055049 (2009).

[2] Quantum Computation with Trapped Polar Molecules, D. DeMille, Phys. Rev. Lett. 88, 067901 (2002).[3] A toolbox for lattice-spin models with polar molecules, A. Micheli, G.K. Brennen, P. Zoller, Nat. Phys. 2, 341 (2006).[4] A High Phase-Space-Density Gas of Polar Molecules, K.K. Ni, S. Ospelkaus, M.H.G. de Miranda, A. Pe’er, B. Neyenhuis,

J.J. Zirbel, S. Kotochigova, P.S. Julienne, D.S. Jin, J. Ye, Science 322 (5899), 231 (2008).[5] Quantum Gas of Deeply Bound Ground State Molecules, J.G. Danzl, E. Haller, M. Gustavsson, M.J. Mark, R. Hart, N.

Bouloufa, O. Dulieu, H. Ritsch, H.C. Nagerl, Science 321 (5892), 1062 (2008).[6] An ultracold high-density sample of rovibronic ground-state molecules in an optical lattice, J. Danzl, M.J. Mark, E. Haller,

M. Gustavsson, R. Hart, J. Aldegunde, J.M. Hutson, H.C. Nagerl, Nature Phys. 6, 265 (2010).

∗Electronic address: [email protected]; URL: http://massey.dur.ac.uk/slc/index.html

6

Matter wave interference with complex molecules

S. Eibenberger1, ∗ and S. Gerlich,1 J. Tuxen,2 S. Nimmrichter,1

M. Tomandl,1 K. Hornberger,3 M. Mayor,2,4 and M. Arndt1

1Vienna Center for Quantum Science and Technology (VCQ), University of Vienna,Faculty of Physics, Boltzmanngasse 5, 1090 Vienna, Austria

2Department of Chemistry, University of Basel, St. Johannsring 19, CH-4056 Basel, Switzerland3Max Planck Institute for the Physics of Complex Systems, Nothnitzer Str. 38, D-01187 Dresden

4Karlsruhe Institute of Technology (KIT), Institute for Nanotechnology, P.O. Box 3640, D-76021 Karlsruhe, Germany

We present new molecule interference experiments with special focus on molecular qualities such as mass, complexityand electric properties. The experiments with a variety of large organic molecules are performed in a Kapitza-Dirac-Talbot-Lau interferometer [1]. De Broglie coherence is to first order only associated with the center-of-mass motion ofthe diffracted particle, in the presence of external fields, however, the delocalized molecules inside the interferometercan be influenced and internal electric properties become accessible [2, 3]. We explore the relevance of internalproperties for the coherence of the matter waves and discuss the possibly detrimental effects. Recent moleculeinterference experiments are presented.

[1] A Kapitza-Dirac-Talbot-Lau interferometer for highly polarizable molecules, S. Gerlich, L. Hackermuller, K. Hornberger, A.Stibor, H. Ulbricht, M. Gring, F. Goldfarb, T. Savas, M. Muri, M. Mayor, and M. Arndt, Nature Physics 3 (2007).

[2] Influence of conformational molecular dynamics on matter wave interferometry, M. Gring, S. Gerlich, S. Eibenberger, S.Nimmrichter, T. Berrada and M. Arndt, H. Ulbricht, K. Hornberger, M. Muri and M. Mayor, M. Bockmann, N. L. Doltsinis,Phys. Rev. A 81 (2010).

[3] Quantum interference distinguishes between constitutional isomers, J. Tuxen, S. Gerlich, S. Eibenberger, M. Arndt and M.Mayor, Chem. Commun. 46 (2010).

∗Electronic address: [email protected]; URL: http://www.quantumnano.at/

7

Interferometry with Bose-Einstein Condensates in microgravity

N. Gaaloul,1, ∗ W. Ertmer,1 E. Rasel,1 and the Quantus team1Institute of Quantum Optics, Leibniz University Hannover

Welfengarten 1, 30167 Hannover, Germany

The recent developments in quantum optics transformed atom interferometry from a pure fundamental researchto a powerful technique giving birth to a multitude of new tools in metrology, gravimetry and fundamental physics.Besides the measurement of fundamental constants (fine structure constant, gravitational constants) or the tests offundamental laws (Equivalence Principle), the application of atom interferometers for gravimetry or generally for themeasurement of inertial forces (Earth rotation, acceleration) became a central focus of research.

In order to improve the sensitivity of such measurements, it is necessary to perform experiments with large ob-servation times. In fact, the sensitivity of an inertial sensor scales with the square of the time the atoms spend inthe interferometer [1]. In this talk, we report about the results reached within the Quantus project in developinga miniaturized and robust experiment using ultra-cold atoms in a free falling elevator as a test-bed for matter-waveinterferometry on long timescales. More than 200 experiments were successfully performed in microgravity and a BECwas observed after free expansions of up to 1s [2]. The implementation of an atom interferometer operating with aBose-Einstein Condensate was recently demonstrated (see Fig. 1). Within the project, the next step is to operate a2-species atom interferometer to perform a test of the Einstein’s Equivalence Principle. These experiments pave theway in the direction of utilizing the technology of matter-wave interferometry for future space missions.

FIG. 1: Typical fringes observed after a 100 ms Bragg interferometry experiment consisting in applying two pulses to split andrecombine a Bose-Einstein condensate.

The QUANTUS project is supported by the German Space Agency DLR with funds provided by the FederalMinistry of Economics and Technology (BMWi) under grant number DLR 50 WM 1131.

[1] Atom Interferometry, P. R. Berman, Ed., Academic Press, San Diego, CA (1997).[2] Bose-Einstein Condensation in Microgravity, T. van Zoest et al., Science 328, 1540 (2010).


8

Bright Matter-Wave Soliton Collisions with Controlled Relative Phase

S. A. Gardiner,1 T. P. Billam,1 and S. L. Cornish1

1Department of Physics, Durham University, South Road, Durham DH1 3LE, United KingdomTel +44 191 334 3683, Fax +44 191 334 5823

Experiments to generate bright matter-wave solitons [1–3] often involve a sudden projection of the system into ahighly non-equilibrium configuration, out of which multiple discrete density peaks settle, which are interpreted assolitons [3]. However, an essential property of true solitons (as opposed to solitary waves) is their robustness tocollisions [4], a robustness which is weakened in a phase-dependent manner as one departs from the quasi-1D limit[5]. We propose a method to split the ground state of an attractively interacting atomic Bose-Einstein condensateinto two bright solitary waves with controlled relative phase and velocity [6]. We analyze the stability of these wavesagainst their subsequent re-collisions at the center of a cylindrically symmetric, prolate harmonic trap as a function ofrelative phase, velocity, and trap anisotropy. We show that the collisional stability is strongly dependent on relativephase at low velocity, and we identify previously unobserved oscillations in the collisional stability as a function ofthe trap anisotropy. An experimental implementation of our method would determine the validity of the mean fielddescription of bright solitary waves, and could prove an important step towards atom interferometry experimentsinvolving bright solitary waves.

FIG. 1: Soliton generation with controlled relative phase, in the quasi-1D limit. Panels (a–f) show the evolution of 1D GPEwith dimensionless trap frequency ω = 0.02 [ω = 0 inset in (a–d)] and relative phase Φ = 0 and (where k quantifies the relativemomentum of the two solitons) k = 0 (a), k = 2 (b), k = 4 (c), k = 6 (d), and Φ = π and k = 4 (e), k = 6 (f). Particle model[4] soliton trajectories are overlaid as lines in (c–f). Panels (e) and (f) reproduce (c) and (d) for the case Φ = π to show thedifference in collision profile. Figure taken from [6]

[1] Formation of a Matter-Wave Bright Soliton, L. Khaykovich, F. Schreck, G. Ferrari, T. Bourdel, J. Cubizolles, L. D. Carr,Y. Castin, C. Salomon, Science 296, 1290 (2002).

[2] Formation and Propagation of Matter-Wave Soliton Trains, K. E. Strecker, G. B. Partridge, A. G. Truscott, R. G. Hulet,Nature 417, 150 (2002).

[3] Formation of Bright Matter-Wave Solitons during the Collapse of Attractive Bose-Einstein Condensates, S. L. Cornish, S.T. Thompson, C. E. Wieman, Phys. Rev. Lett. 96, 170401 (2006).

[4] Bright Matter-Wave Soliton Collisions in a Harmonic Trap: Regular and Chaotic Dynamics, A. D. Martin, C. S. Adams,S. A. Gardiner, Phys. Rev. Lett. 98, 020402 (2007).

[5] Bright Solitary Waves and Trapped Solutions in Bose Einstein Condensates with Attractive Interactions, N. G. Parker, S.L. Cornish, C. S. Adams, A. M. Martin, J. Phys. B 40, 3127 (2007).

[6] Realizing Bright Matter-Wave Soliton Collisions with Controlled Relative Phase, T. P. Billam, S. L. Cornish, S. A. Gardiner,arXiv:1010.3219.

9

New determination of the fine structure constant and test of the quantumelectrodynamic

R. Bouchendira,1 P. Clade,1 S. Guellati-Khelifa,1, 2, ∗ F. Nez,1 and F. Biraben1

1 Laboratoire Kastler Brossel, Ecole Normale Superieure, Universite Pierre et Marie Curie, CNRS2Conservatoire National des Arts et Metiers, 292 rue Saint Martin, 75141 Paris Cedex 03, France

The fine structure constant α is the basic constant of the quantum electrodynamics theory (QED). For instance,this theory relates the electron anomaly ae to α by :

ae = A1

(απ

)+ A2

(απ

)2

+ A3

(απ

)3

+ A4

(απ

)4

+ ... + aµ,τ + ahadronic + aweak (1)

the values of Ak and aµ,τ come from QED calculations, the terms ahadronic and aweak include the small hardronicand weak contributions. Besides, the electron anomaly is determined experimentally with a relative uncertainty of0.28 x 10−12 by measuring the cyclotron and the spin frequencies of electron in a cylindrical Penning trap [1]. Acomparison of this experimental value to the theoretical one provided by using an accurate and QED independentdetermination of the fine structure constant is a powerful test of QED.

The principle of our experiment has been described previously[2]. It combines a Ramsey-Borde atom interferometerwith Bloch oscillations (BO) to provide a precise measurement of the recoil velocity (vr = hk/mRb) of a Rubidiumatom when it absorbs a photon of momentum hk. The fine structure constant is then deduced using the value of theratio h/mRb thanks to the relation:

α2 =2R∞c

mRb

me

h

mRb, (2)

The electron mass me and the Rydberg constant R∞ are known with an uncertainty better than the one of limitingfactor h/mRb.

FIG. 1: Left figure: in blue, relative contributions to the electron anomaly of the different terms of equation (1), in red theiruncertainties. Right figure: comparison of the measurements of the electron anomaly with the theoretical value obtained byusing the new value of α (label Rb 2010). The point ”Rb 2010 - only QED” is obtained without the three last terms of (1).

In this talk we present a new determination of the fine structure constant, with a relative uncertainty of6.6 x 10−10[3]. This value improves our precedent result by a factor of about seven [2]. Using this determination,we obtain a theoretical value of the electron anomaly in agreement with the experimental measurement of Harvardgroup. The comparison of these values provides the most stringent test of the QED. Moreover, the uncertainty issmall enough to verify for the first time the muonic and hadronic contributions to this anomaly.

[1] D. Hanneke, S. Fogwell and G. Gabrielse, Phys. Rev. Lett. 100, 120801 (2008).[2] M. Cadoret, E. de Mirandes, P. Clade, S. Guellati-Khelifa, C. Schwob, F. Nez, L. Julien, and F. Biraben, Phys. Rev. Lett.

101,230801 (2008).[3] R. Bouchendira, P. Clade, S. Guellati-Khelifa, F. Nez and F. Biraben,, accepted for publication in Phys. Rev. Lett..


10

Three-body loss and three-body correlations in one-dimensional systems

E. Haller,1, ∗ M.J. Mark,1 J.G. Danzl,1 M. Rabie,1 K. Lauber,1 G. Pupillo,2, 3 and H.-C. Nagerl1

1Institut fur Experimentalphysik und Zentrum fur Quantenphysik, Universitat InnsbruckTechnikerstrasse 25/4, 6020 Innsbruck, AustriaTel +43 512 507-6306, Fax +43 512 507-2921

2Institut fur Theoretische Physik, Universitat Innsbruck, Technikerstraße 25,A–6020 Innsbruck, Austria

3Institut fur Quantenoptik und Quanteninformation der OsterreichischenAkademie der Wissenschaften, Technikerstraße 21a, A–6020 Innsbruck, Austria

We load a Bose-Einstein condensate of cesium atoms into an array of tube-like 1D traps generated by a 2D opticallattice potential, and we control the interaction strength by means of a 1D confinement-induced resonance [1]. Unlikefor ultracold atoms in 3D geometry, which show a dramatic increase of three-body losses in the proximity of aFeshbach resonance, we observe a strong suppression of three-body losses in 1D. This suppression originates fromthe fermionization of the particles for strong repulsive interactions, and it can be quantized by the three-particlecorrelation function g3 at close distances. We observe a reduction of g3 by three orders of magnitude for an increasinginteraction parameter γ, and we find excellent agreement of g3(γ) with theoretical predictions [2].

[1] E. Haller, et al., Phys. Rev. Lett. 104 153203 (2010).[2] D. Gangardt, and G. Shlyapnikov, Phys. Rev. Lett. 90 10401 (2003).

∗Electronic address: [email protected]; URL: http://www.ultracold.at

11

Setting up an all optical time domain Talbot-Lau Interferometer for large metalclusters

Philipp Haslinger, Nadine Drre, Philipp Geyer, Jonas Rodewald, Stefan Nimmrichter and Markus ArndtFaculty of Physics, University of Vienna, Boltzmanngasse 5, A 1090 Vienna, Austria

Klaus Hornberger

Max-Planck Institute for the Physics of Complex Systems, Dresden

Bernd v. IssendorffUniversitat Freiburg

The quantum superposition principle for atomic and molecular matter is an essential ingredient of quantum physics.Throughout the last decades research has tried to explore this very useful property of quantum physics and hasexpanded it to more and more complex matter. Also applications, like metrology and mass spectrometry, benefitenormously of quantum delocalization of particles [1, 2]. Further extensions to the coherent manipulation of largerclusters and hot complex molecules require special experimental conditions. We discuss a new all-optical time domainTalbot-Lau interferometer consisting of three pulsed laser gratings. It promises to shift matter wave interferometry tomasses even beyond the limit of a million atomic mass units [3]. We will illustrate the advantages of interferometry inthe time domain: How such an interferometer can become an important tool for exploring fundamental decoherenceand dephasing phenomena. How the time domain provides more accuracy for precision metrology of electromagneticor structural properties of nanoparticles [4].

[1] A. Cronin, D. Pritchard, J. Schmiedmayer, Optics and interferometery with atoms and molecules, Rev. Mod. Phys. 81, 3,1051-1129 (2009)

[2] Tuxen et al., Quantum interference distinguishes between constitutional isomers, Chem. Comm. 46, 4145-4147 (2010)[3] Reiger et al. Exploration of gold nanoparticle beams for matter wave interferometry, Opt. Comm. 264, 326-332 (2006)[4] Nimmrichter et al., Concept of a time-domain ionizing matter-wave interferometer, submitted (2010)

12

GAIN — a high-precision mobile gravimeter based on atom interferometry

M. Hauth,1, ∗ M. Schmidt,1 A. Senger,1 C. Freier,1 V. Schkolnik,1 and A. Peters1

1Institut fur Physik, AG optische Metrologie, Humboldt Universitat zu BerlinNewtonstr 15, 12489 Berlin, Germany

Tel +49 30 2093-4907, Fax +49 30 2093-4718

Since 1991, matter wave interferometry has been used in many laboratories for a variety of fundamental physicsexperiments, e.g. measurements of the fine-structure and gravitational constants. However, due to the complexityof these experiments, they were confined to laboratory environments. Only later, efforts have been undertaken todevelop mobile atom interferometers. These new sensors open up the possibility to perform on-site high-precisionmeasurements of rotations, gravity gradients as well as absolute accelerations.

GAIN (Gravimetric Atom Interferometer) is a mobile and robust gravimeter that is being developed within theframework of the EuroQUASAR/IQS programme. It is based on interfering ensembles of laser cooled 87Rb atoms inan atomic fountain configuration with a height of one meter. With a targeted accuracy of a few parts in 1010 for themeasurement of local gravity g this instrument will offer about an order of magnitude improvement in performanceover the best currently available absolute gravimeters. Together with the capability to perform measurements directlyat sites of geological interest, this opens up the possibility for a number of interesting applications in fields such asgeodesy, geophysics or seismology.

This talk will review the working principle of our atomic gravimeter and present some of the most importantsubsystems. These include a highly adaptable vacuum chamber, a rack-mounted laser-setup and an active vibrationisolation stage. Furthermore, we report on the first transport of the GAIN instrument and subsequent gravitymeasurements at the new site. The sensitivity of this measurement was high enough to allow for the identification ofa variety of local gravitational effects. The data also is in good agreement with theoretical predictions obtained fromgeophysical models commonly used in gravimetry.

We outline further steps necessary to reach the targeted accuracy and give an outlook on current developments inlaser system miniaturization. Finally, we discuss potential applications and plans for the gravimeter’s first measure-ment campaign at sites of geological interest.

∗Electronic address: [email protected]; URL: http://www.physik.hu-berlin.de/qom

13

Coherence and chiral order in higher bands of an optical lattice

M. Olschlager,1 G. Wirth,1 and A. Hemmerich1

1Institut fur LaserphysikUniversitat Hamburg

Luruper Chaussee 149, 22761 Hamburg, Germany

Atoms trapped in optical lattices have been used successfully to study many-body phenomena. But the shapethat bosonic ground-state wavefunctions can take is limited, compromising the usefulness of this approach. Suchlimitations, however, do not apply to excited states of bosons. Atomic superfluids realized in higher-energy bands,where orbital degrees of freedom are essential, promise to provide insight into a wider range of many-body effects. Iwill discuss our observations of chiral order parameters in the Pand F-bands, which brake the lattice symmetry andtime-reversal symmetry.

14

A tunable few-fermion system

S. Jochim,1, ∗ F. Serwane,1 G. Zurn,1 T. Lompe,1 T.B. Ottenstein,1 M. Ries,1 and A. N. Wenz1

1Physikalisches Institut, Universitat HeidelbergPhilosophenweg 12, 69120 Heidelberg, GermanyTel +49 6221 516 229, Fax +49 6221 516 604

As the building blocks of matter, few-fermion systems such as atoms and nuclei play an essential role in nature.We have prepared artificial systems containing 1-10 atoms with exquisit control over the many-body quantum statewith fidelities exceeding 90%. Such systems are particularly interesting as the interaction strength can be tuned usingFeshbach resonances, enabling the realization of strongly correlated few-body systems.

We prepare these systems starting from a degenerate spin mixture of 6Li atoms in an optical dipole trap. Withthis trap we overlap a µm-sized tightly focused dipole trap resulting in a substantial enhancement of the degeneracyinside the microtrap. After thermalization we remove the reservoir that contains some 104 atoms. We spill most ofthe remaining ∼600 atoms in a controlled way by applying a tilt to the microtrap using a magnetic field gradient,such that only very few quantum states remain in the trap (see Fig. 1) [1].

In a first set of experiments we compare the energy of two distinguishable fermions in the ground state (spin up anddown) with tunable repulsive interactions to the energy of two identical spin-up fermions in the two lowest vibrationalstates. In this way we identify the point where the two distinguishable atoms become ”fermionized”, i.e., they possessthe same spatial correlations as the identical ones.

Next steps include the study of attractive systems, where one expects to observe a paring gap that strongly dependson the exact particle number.

a

b

3.4 3.2 3.0 2.8 2.60

2

4

6

8

10

Variance

Mea

n at

om n

umbe

r

Trap depth (relative scale)0 0.5 1.0

c

FIG. 1: a) Starting from a degenerate two-component Fermi gas of about 600 atoms in the trap, we create few-particle samplesby adiabatically deforming the potential to spill atoms in higher levels. After the potential has been restored, the system endsup in a well defined few-particle quantum state. b) When the trap depth is reduced the mean atom number decreases in stepsof two since each energy level in the trap is occupied with one atom per spin state. c) For even atom numbers, the numberfluctuations are strongly suppressed.

[1] Deterministic preparation of a tunable few-fermion system, F. Serwane, G. Zurn, T. Lompe, T. B. Ottenstein, A. N. Wenz,S. Jochim, http://arxiv.org/abs/1101.2124 (2011).

∗Electronic address: [email protected]; URL: www.lithium6.de

15

Quantum metrology with cold atoms

M. Kasevich1

1Department of Physics, Stanford University, Stanford, California 94305

This talk will summarize recent efforts to push the precision frontier for atom interferometry. These includedevelopment of a 10 m tall atomic fountain apparatus for tests of the equivalence principle and post-Newtoniangravitation and a proposed space-based gravity-wave antenna operating in the 10 mHz to 10 Hz band (AGIS).

A cavity QED system based on cold atoms has been used to demonstrate a Raman laser operating at the boundaryof the superradiant regime. The observed inter-mode beatnote between the TEM10 and TEM01 has a linewidthof ∼ 120 Hz. This laser may have precision sensing applications, eg. as a ring laser gyroscope or possibly as agravity-wave detector.

16

Pair correlated matter waves for quantum interferometry

Carsten Klemp1

1Institute for Quantum OpticsLeibniz Universitaet Hannover

Matter wave optics with ultra cold samples has reached the point where non-classical states can be prepared andtheir fascinating properties can be explored. In optics, parametric down conversion is routinely used to generate lightwith squeezed observables as well as highly entangled photon pairs. The applications of these nonclassical states rangefrom fundamental tests of quantum mechanics to improved interferometers and quantum computation. Therefore, itis of great interest to realize such nonclassical states with matter waves. Bose-Einstein condensates with non-zerospin can provide a mechanism analogous to parametric down conversion, thus enabling the generation of non-classicalmatter waves. The process acts as a two-mode parametric amplifier and generates two clouds with opposite spinorientation consisting of the same number of atoms. At a total of ∼ 10000 atoms, we observe a squeezing of thenumber difference of -8 dB below shot noise, including all noise sources. A microwave coupling between the twomodes allows for analysis of the created state towards sub-shot-noise interferometry.

17

Cold Atom Interferometers for inertial measurements

A. Landragin,1 Q. Bodart,1 T. Farah,1 C. Garrido Alzar,1 J. Lautier,1 T. Lvque,1

A. Louchet-Chauvet,1 M. Meunier,1 S. Merlet,1 and F. Pereira Dos Santos1

1LNE-SYRTE, Observatoire de Paris, CNRS and UPMC, 61 avenue de lobservatoire,F-75014 Paris, France

Atomic interferometers have shown to be highly accurate and stable inertial sensors. Therefore, high precisionatomic inertial sensors find scientific applications in the areas of general relativity, geodesy and in the field of naviga-tion. In such devices, the interferometer directly measures the relative acceleration or rotation between the referentialframe of the laboratory, realized by the lasers, and the referential frame of the atoms in free fall. The quality ofthe measurement relies on the very good knowledge of the wavelength of the lasers, which are used to measure thedisplacement of the atoms.

Nevertheless, experimental defects in the realization of the lasers may limit the performances. A good control ofthe trajectories of cold atoms, of the phases of the lasers and of the interactions between atomic wave-packets andtheir beam splitters are then mandatory. This has been confirmed experimentally on our cold atom gyroscope andgravimeter. The main limit to the accuracy and the long term stability appears to be the wave-front distortions ofthe lasers used for the beam splitters. It is not fundamental but have to be taken into account to achieved ultimatelimits of such inertial sensors.

Finally, these developments lead to the possibility of using such atom interferometer to test fundamental physic andespecially the law of gravity. Most of these projects benefit from weightlessness and then need special developmentsand tests to make them transportable and compatible with such environment. Some tests of an atom interferometerin a 0-g plane will be presented.

18

Strongly interacting bosons in a 1D optical lattice at incommensurate densities

A. Lazarides,1, 2 O. Tieleman,2 and C. Morais Smith2

1Max Planck Institute for the Physics of Complex Systems,Noethnitzer Str. 38, D-01187 Dresden, Germany.

2Institute for Theoretical Physics, Utrecht University,Leuvenlaan 4, 3584 CE Utrecht, The Netherlands.

We investigate quantum phase transitions occurring in a system of strongly interacting ultracoldbosons in a 1D optical lattice. After discussing the commensurate-incommensurate transition, wefocus on the phases appearing at incommensurate filling. We find a rich phase diagram, withsuperfluid, supersolid and solid (kink-lattice) phases. Supersolids generally appear in theoreticalstudies of systems with long-range interactions; our results break this paradigm and show that theymay also emerge in models including only short-range (contact) interactions, provided that quantumfluctuations are properly taken into account.

PACS numbers:

19

The Strontium Optical Lattice Clock at PTB

Ch. Lisdat,1, ∗ St. Falke,1 Th. Middelmann,1 St. Vogt,1 F. Riehle,1 and U. Sterr1

1Physikalisch-Technische BundesanstaltBundesallee 100, 38116 Braunschweig, GermanyTel +49 531 592-4326, Fax +49 531 592-4305

Optical lattice clocks with strontium have reached fractional systematic uncertainties of 1.5×10−16 and instabilitiesof 2×10−15 at one second averaging time [1]. The frequency of the 87Sr clock transition 1S0− 3P0 has been measuredso far at three institutions [2]. The results agree within their uncertainties, which are largely determined the respectiveCs clock used as reference. The strontium clock is, among others, approved as Secondary Representation of the Secondby the International Committee for Weights and Measure (CPEM) [3].

Here we report on our setup of an optical lattice clock and on our recent optical frequency measurement of thestrontium lattice clock at PTB. The Sr lattice clock was operated with spin polarised atoms that were loaded by atwo-stage laser cooling sequence into a horizontally oriented 1D optical lattice operated at the magic wavelength. Atthe magic wavelength the ac-Stark shift of both clock levels is equal such that no net light shift appears on the clocktransition. The optical lattice provides the strong confinement to interrogate the atoms without Doppler and recoilshift. A diode laser with 1 Hz linewidth and a free-running short term drift of a few 10 mHz/s is used to excitethe atoms. The signal is used to stabilize the frequency to the centre of the clock transition. The frequency of theclock laser was counted by a fs-frequency fibre comb referenced to a caesium fountain clock, which is the nationalprimary standard for time and frequency. A preliminary evaluation shows a good agreement with the results fromother labs. We estimate an uncertainty of 3 × 10−16 from the PTB Sr lattice clock. The statistical and systematicuncertainties of the Cs fountain during the measurement add up to 10 × 10−16. Since several Sr lattice clocksworldwide have demonstrated uncertainties below the uncertainty of the Cs clocks the necessity of direct opticalfrequency comparisons increases.

Currently, a leading contribution to the uncertainty budget is due to uncertainties of the ac-Stark shift induced byambient black body radiation. This effect contributes with 1×10−16 to the fractional uncertainty [1]. This uncertaintycontains equal contributions from the 1 K uncertainty of the effective ambient temperature at the position of theatoms and from the uncertainty of the shift coefficient, obtained from atomic structure calculations [4]. To reduce thisuncertainty we have set up an experiment to transport ultra-cold atoms in the magic-wavelength optical lattice froman open loading zone to well controlled environments [5]. First, we plan to measure the differential static polarizabilityin a dc electric field. As the polarizability is closely related to the blackbody shift, this measurement will reduce theuncertainty of the shift coefficient. In a second approach, by moving the atoms into an environment at liquid nitrogentemperature, the blackbody shift can be largely reduced (3×10−17) and measured directly by comparison with a roomtemperature measurement. Here we will discuss details of the blackbody shift and report on the progress towards,both, direct and indirect measurements of the blackbody radiation shift.

The work is supported by the Centre for Quantum Engineering and Space-Time Research (QUEST), ESA, DLR,and the ERA-NET Plus Program.

[1] A. D. Ludlow et al., Science 319, 1805 (2008).[2] X. Baillard et al., Eur. Phys. J. D 48, 11 (2008); G. K. Campbell et al., Metrologia 45, 539 (2008);

F.-L. Hong et al., Opt. Lett. 34, 692 (2009).[3] P. Gill and F. Riehle, in Proceedings of the 2006 Meeting of the European Frequency and Time Forum

(http://www.eftf.org/previousmeetings.php), pp. 282–288.[4] S. G. Porsev and A. Derevianko, Phys. Rev. A 74, 020502 (2006).[5] T. Middelmann et al., Tackling the blackbody shift in a strontium optical lattice clock, arXiv:1009.2017 [physics.atom-ph]

10 Sep 2010, to appear in IEEE Trans. Instrum. Meas.

∗Electronic address: [email protected]; URL: http://www.ptb.de

20

Exploring the physics of disorder with a tunable Bose-Einstein condensate

G. Modugno1, ∗

1LENS, University of FlorenceVia Nello Carrara 1, 50019 Sesto Fiorentino, Italy

The combination of disorder and nonlinearities determines the transport properties of many physical systems,including normal conductors and superconductors, biological systems, or light in disordered nonlinear media. Whilea full understanding of the interplay of disorder and nonlinearities has long been sought, the lack of complete controlover experimental parameters in most systems makes systematic investigations difficult, and there are still severalopen questions.

I will describe how in recent experiments [1-3] we have employed Bose-Einstein condensates with tunable interactionsin combination with optical potentials to address some of the open questions, related for example to the transportproperties and to the transition from insulating to superfluid phases. In particular, we have observed the crossover froman Anderson insulator to a Bose-Einstein condensate induced by a repulsive interaction by studying the momentumdistribution and the correlation function. In addition, we have characterized the subdiffusive transport dynamics thatarises from the interplay of interaction and disorder. I will also discuss prospects for further experiments in the regimeof strong interaction.

∆/J

Eint

/J

g(4.

4 d)

AG fBEC

BEC

b

0.1 11

4

10

40

0.0

1.0

FIG. 1: Correlation of neighboring states of a Bose-Einstein condensate in a quasiperiodic lattice.

[1] Delocalization of a disordered bosonic system by repulsive interactions, B. Deissler, M. Zaccanti, G. Roati, C. D’Errico, M.Fattori, M. Modugno, G. Modugno, M. Inguscio, Nature Physics 6, 354-358 (2010).

[2] Correlation function of weakly interacting bosons in a disordered lattice, B. Deissler, E. Lucioni, M. Modugno, G. Roati, L.Tanzi, M. Zaccanti, M. Inguscio, G. Modugno, arXiv:1010.0853.

[3] Observation of subdiffusion of a disordered interacting system, E. Lucioni, B. Deissler, L. Tanzi, G. Roati, M. Modugno, M.Zaccanti, M. Inguscio, G. Modugno, arXiv:1011.2362.


21

Coherent control of dressed matter waves in strongly driven periodic potentials

O. Morsch,1, ∗ D. Ciampini,2 and E. Arimondo2

1INO-CNR, Largo Bruno Pontecorvo 3, I-56127 Pisa, ItalyTel +39 050 2214569

2Dipartimento di Fisica and CNISM, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy

The response of a quantum system to an explicitly time-dependent variation of its parameters may be highly non-trivial even if the properties of the static system are well known, and qualitatively new states can appear that wereabsent in the original system. In the case of matter waves the effects of the driving can either be described in terms ofFloquet quasienergy states or via the more physically intuitive picture of ”dressed matter waves”. In analogy with thedressed atom picture of an atom in a strong radiation field, for macroscopic matter waves in driven periodic potentialsthe dressing is provided by the oscillatory motion of the lattice potential. Such dressed matter waves can exhibit newproperties and thus allow enhanced control of their quantum states.

In my talk I will present experiments on Bose-Einstein condensates in strongly driven 1, 2 and 3-D optical lattices.We have demonstrated [1, 2] that by controlling the strength of the periodic driving, the amplitude as well as thesign of the matrix element for tunneling between adjacent sites of the lattice can be controlled. We have also usedthis fully coherent control in order to induce a superfluid-Mott insulator transition in a driven 3-D lattice [3]. Theprospects for future experiments based on the coherent control of tunneling will be discussed.

FIG. 1: (a) Principle of the coherent control of tunneling in strongly driven optical lattices. Rather than changing the tunnelingmatrix element by varying the lattice depth (left), one can control the tunneling by shaking the lattice (right). (b) Experimentalsetup for a driven 3-D optical lattice using piezo-electric transducers for driving the lattice.

[1] Dynamical Control of Matter-Wave Tunneling in Periodic Potentials, Lignier H., Sias C., Ciampini D., Singh Y., ZenesiniA., Morsch O., Arimondo E., Phys. Rev. Lett. 99, 220403 (2007).

[2] Observation of Photon-Assisted Tunneling in Optical Lattices, Sias C., Lignier H., Singh Y. P., Zenesini A., Ciampini D.,Morsch O., Arimondo E., Phys. Rev. Lett. 100, 040404 (2008).

[3] Coherent Control of Dressed Matter Waves, Zenesini A., Lignier H., Ciampini D., Morsch O., Arimondo E., Phys. Rev.Lett. 102, 100403 (2009).

∗Electronic address: [email protected]; URL: http://www.df.unipi.it/gruppi/arimondo/index.htm

22

Quantum Atom Optics: Spin squeezed states and atomic two-mode squeezed vacuum

Markus Oberthaler1, ∗

1Kirchhoff Institut fur Physik und Zentrum fur Quanten Dynamik, Universitat HeidelbergIm Neuenheimer Feld 227, 69115 Heidelberg, Germany

Tel +49 6221 54 5170, Fax +49 6221 54 5179

Bose Einstein condensates allow the experimental implementation of very different routes for the deterministicgeneration of atomic entanglement. Here we report on two different routes to generate highly entangled statesemploying inter-species Feshbach enhanced interactions as well as spin changing collisions.

For the generation of spin squeezed states we employ two hyperfine ground states of Rubidium which can be coupledvia a two photon transition. By tuning a magnetic field close to a Feshbach resonance the system can be realizedin the miscible regime with significant interaction between the two species. With that system 8.3dB spin squeezing[1] has been realized. The high level of experimental control leads to an almost Heisenberg limited squeezed statewhich implies strong many particle entanglement. Employing the entanglement witness for the depth of entanglementdeveloped by Sørenson and Mølmer [2] one can claim that at least 80 particles out of 400 are entangled within threesigma confidence level. With this massive quantum resource it was possible to demonstrate explicitly the improvementof a Ramsey type matterwave interferometer beyond the classical precision limit. Since the squeezing is realize withinthe first beamsplitter of the interferometer while the input state is a classical coherent state we refer to this setup asnonlinear matterwave interferometer.

For the generation of mode entangled states we have employed spin changing collisions in a situation where thesingle external mode approximation can be applied. Beside the observation of 12dB suppression below shot noise ofparticle number difference fluctuations we have also extracted information about the sum of the phases of the fieldsin the two modes. This has been achieved by implementing a novel homodyning technique allowing for measuringone of the di-atom quadratures. The observations reveal that continuous variable entanglement classified as Einstein-Podolsky-Rosen entanglement [3] is present.

[1] Nonlinear atom interferometer surpasses classical precision limit, C. Gross, T. Zibold, E. Nicklas, J. Esteve and M. K.Oberthaler, Nature 464, 1165 (2010).

[2] Entanglement and extreme spin squeezing, A. Sørensen, and K. Mølmer, Phys. Rev. Lett. 86, 4431 (2001).[3] The Einstein-Podolsky-Rosen paradox: from concepts to applications, M. Reid et al. Rev.Mod.Phys. 81, 1727 (2009).

∗Electronic address: [email protected]; URL: http://www.matterwave.de

23

Cold atoms in a 1D periodically driven system

D. Poletti1, ∗ and C. Kollath1

1Departement de Physique Theorique, Universite de Geneve,24 quai Ansermet, CH-1211 Geneve, Switzerland

Tel +41 22 37 96154, Fax +41 22 37 96132

We study the driving of a one-dimensional ultracold quantum gases an optical lattice. The driving is a periodictranslation of the lattice potential in space. If the lattice itself is quickly shaken this induces effectively a changeof the tunneling constant between neighboring lattice sites. This has also been recently verified experimentally. Westudy how the presence of such a driving affects the different quantum states that can emerge in a one-dimensionalsystem.

∗Electronic address: [email protected]; URL: http://theory.physics.unige.ch/dpt/showlargimage.php?id=437

24

Quantum optics with cold quantum gases

Helmut Ritsch1

1University of Innsbruck, Innsbruck, Austria

As matter influences the propagation of light waves, light can be used to manipulate matter waves. In typicalsituations as optical traps or cavity QED one of the two effects dominantes. However, confining a cold gas in a highfinesse optical resonator creates a novel situation, where particles and photons dynamically influence their motion bymomentum exchange on equal footing. The particles create a dynamic refractive index diffracting the light waves,which interfere and in turn form structured optical potentials guiding the particles motion. The ultimate limit of aquantum degenerate gas in an optical lattice inside a cavity represents a key model for quantum optics with quantumgases, where a quantum description of both light and atomic motion is equally important. Due to the dynamicalentanglement of atomic motion and light, the measurement of the scattered light detects atomic quantum statisticsand projects the many-body atomic state. For a generic case we present an analytical solution for this measurementdynamics valid for macroscopic Bose-Einstein condensates (BEC) with large atom numbers. The theory can be wellapplied for optical large optical lattices or even a BEC in a double-well potential.[1] Beyond measurement dynamicswe study the selfconsistent light forces on high field seeking atoms between two mirrors. Above a certain thresholdillumination intensity the particles order in a regular crystalline structure, where they form ordered periodic patternswith Bragg planes optimally coupling the pump laser into the resonator[2]. At T 0 this model shows a quantum phasetransition analogous to the Dicke phase transition and the resulting atomic state exhibits typical characteristics of asupersolid.

FIG. 1: a) Scheme for optical probing of atoms in a lattice b) Selforganized distribution of a BEC in an optical lattice

The work was supported by the Austrian Science Fund FWF (P20391 and F4013).

[1] I. B. Mekhov, C. Maschler, and H. Ritsch, Nature Phys. 3, 319 (2007)[2] P. Domokos and H. Ritsch, Phys. Rev. Lett. 89, 253003 (2002)

25

Spin self-rephasing and very long coherence times

P. Rosenbusch1

1LNE-SYRTE, Observatoire de Paris, Paris, France

Atomic clocks, nuclear magnetic resonance and other precision techniques are based on the coherent manipulationof an ensemble of spins 1/2. Highest sensitivity requires narrow linewidth and good signal-to-noise i.e. long coherencetimes and the interrogation of many spins. Usually these are contradictory as interactions destroy coherence and fieldgradients create dephasing. Known mechanisms to battle dephasing include experimental techniques like spin-echoor interaction-driven random fluctuations leading to motional narrowing and exchange narrowing.

Here we present a new deterministic mechanism that may be seen as a continuous intrinsic spinecho. In contrast toexchange narrowing, the exchange interaction results in a deterministic rotation of two spins around their sum. Manyof such identical spin rotations (ISR) eventually result in spin-rephasing. The mechanisms two simple ingredients,particle indistinguishability and exchange interaction, are of such fundamental nature that a wide observation of ourmechanism is expected.

We perform Ramsey spectroscopy on the ground state of ultracold 87Rb atoms magnetically trapped on a chipin the Knudsen regime. The compensation of 2nd order Zeemann effect and mean field shift is employed to reducefield inhomogeneities over the sample to 80 mHz [1]. This should limit the 1/e contrast decay time to about 3 s inagreement with previous work, while decay times of 58+/-12 s are actually observed [2]. Furthermore, slightly offthe compensation point, we observe contrast revivals increasing with atom density, which reveal our mechanism asdeterministic and interaction driven. Solving a kinetic equation for the spin variables based on the ISR, we obtain goodagreement with the data. Our findings are reminiscent of earlier calculations for a trapped gas which predict localizedpolarization revivals and synchronization within spatial domains in the hydrodynamic regime. This similarity baresa first indication of the general nature of our mechanism.

The long coherence times open a truly new approach to higher spectral resolution in many applications. We presentour trapped atom clock on a chip currently showing a frequency stability of 1.6 10−12 at 1s in a compact set-up [3,4].Technical improvements under way aim towards the full exploitation of the long coherence times, which should gainanother order of magnitude.

[1] P. Rosenbusch, Appl. Phys. B, 95, 227 (2009)[2] C. Deutsch et al., Phys. Rev. Lett, 105, 020401 (2010)[3] C. Lacroute et al., IEEE Trans. Ultrason. Ferroelectr. Freq. Control 57, 106 (2010).[4] F. Ramirez-Martinez et al, Advances in Space Research 47 (2011) in print

26

The MAGIA experiment: status and prospects

G. Rosi,1, ∗ Y.-H. Lien,1 F. Sorrentino,1 G. M. Tino,1 L. Cacciapuoti,2 M. de Angelis,3 and M. Prevedelli4

1Dipartimento di Fisica e Astronomia & INFN, Universita di Firenze,via Sansone 1 50019 Sesto Fiorentino (FI), ItalyTel +39 055 457 2031, Fax +39 055 457 2346

2European Space Research and Technology Centre,Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands

3Istituto di Cibernetica CNR, via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy4Dipartimento di Fisica dell’Universita di Bologna, via Irnerio 46, 40126 Bologna, Italy

Atomic inertial sensors are especially interesting for the attainable accuracy and long term stability. Accelerometersbased on atom interferometry have been developed for fundamental physics experiments as well as for many practicalapplications including metrology, geodesy, geophysics, engineering prospecting and inertial navigation [3].

We will report on the status of the MAGIA experiment for the accurate measurement of the gravitational constantG. The experiment is based on a light-pulse atom interferometry gravity gradiometer detecting the gravitational fieldgenerated by a well characterized set of source masses (fig. 1).

87Rb atoms, trapped and cooled in a magneto-optical trap (MOT), are launched upwards in a vertical vacuum tubewith a moving optical molasses scheme, producing an atomic fountain. Near the apogees of the atomic trajectories, ameasurement of their vertical acceleration is performed by a Raman interferometry scheme. External source massesare positioned in two different configurations (C1 and C2) and the induced phase shift is measured as a function ofmasses positions.

FIG. 1: Left: scheme of the MAGIA experiment. Right: typical Lissajous plots obtained by plotting the phase of the upperinterferometer versus the phase of the lower interferometer, for the C1 and C2 positions of the source masses. The ellipserotation angle is a measure of the gravity gradient change.

Goal of the experiment is to measure G with 100 ppm accuracy. After a preliminary measurement with ∼ 0.1%precision [1], we recently operated several upgrades to apparatus [2]. In particular, we improved the SNR and long termstability/reproducibility ; we also improved the knowledge of sources of systematic error though a careful calibrationof detection efficiencies, atomic trajectories and source masses positions. Fig. 2 shows a typical long-run measurementof the gravity gradient change, as well as some steps of the sensitivity improvement.

We will also briefly discuss the future prospects of the MAGIA experiment as well as other experiments in progress,planned or being considered using ultracold atom gravity sensors.

[1] G. Lamporesi, A. Bertoldi, L. Cacciapuoti, M. Prevedelli, and G. M. Tino, Determination of the Newtonian GravitationalConstant Using Atom Interferometry, Phys. Rev. Lett. 100 050801 (2008).

[2] F. Sorrentino, Y.-H. Lien, G. Rosi, G. M. Tino, L. Cacciapuoti, and M. Prevedelli, and Sensitive gravity-gradiometry withatom interferometry: progress towards an improved determination of the gravitational constant, New. J. Phys. 12 095009(2010).

∗Electronic address: [email protected]; URL: http://coldatoms.lens.unifi.it

27

FIG. 2: Left: (top) Modulation of the differential phase shift measured by the atomic gravity gradiometer when the distributionof the source masses is alternated between configuration C1 (upper points) and C2 (lower points); (down) Resulting values ofthe angle of rotation ∆Φ(i). Right: Allan deviation of the differential inteferometer phase, showing some steps of the sensitivityimprovement.

[3] M. de Angelis et al., Precision gravimetry with atomic sensors, Meas. Sci. Technol. 20 022001 (2009).

28

Clocks, Atom Interferometers, and Tests of the Gravitational Red Shift

C. Salomon,1, ∗ P. Wolf,1 L. Blanchet,1 C. Borde,1 S. Reynaud,1 and C. Cohen-Tannoudji1

1Laboratoire Kastler Brossel, CNRS, Ecole Normale Suprieure, 24 rue Lhomond, 75231 Paris, France

We will discuss tests of the gravitational redshift using clocks or atom interferometers. We will review recentexperiments and point fundamental differences between tests with atomic clocks and tests with atom interferometersthrough the measurement of acceleration of freely falling atoms. In a recent paper, Mller, Peters and Chu have arguedthat atom interferometers provide a very accurate test of the gravitational redshift by considering the atom as a clockticking at the Compton frequency [1]. We show that this analysis is incorrect in the frame of General Relativity and inmost alternative theories of gravity [2, 3]. Atom interferometers allow the measurement of acceleration of gravity andby comparison with a freely falling corner cube provide a test of the universality of free fall. Theoretical frameworks inwhich atom interferometers would constitute a test of the red shift pose dreadful problems as they would violate theprinciple of least action for matter-wave, energy conservation, and standard Quantum Mechanics. No such alternativetheory exists today.

[1] H. Muller, A. Peters, and S. Chu, Nature 463, 926 (2010)[2] P. Wolf, L. Blanchet, C. Bord, S. Reynaud, C. Salomon, and C. Cohen-Tannoudji, Nature 467, E1 (2010)[3] P. Wolf, L. Blanchet, C. J. Bord, S. Reynaud, C. Salomon, and C. Cohen-Tannoudji, arXiv:1012.1194, submitted to Classical

and Quantum Gravity, (2010)


29

Spinor gases in optical lattices

Luis Santos,1, ∗ Karen Rodriguez,1 Arturo Arguelles,1 Maria Colome-Tatche,1 and Temo Vekua1

1Institut fur Theoretische Physik, Leibniz Universitat Hannover, Appelstrasse 2, 30169, Hannover, Germany

Spinor gases, formed by atoms with various available Zeeman substates, provide a rich and interesting physicsdue to the interplay between internal and external degrees of freedom. Spinor gases in optical lattices constitute aninteresting scenario to analyze phenomena resembling quantum magnetism. In this talk I will present some recentresults concerning spin-3/2 fermions and spin-1 bosons in 1D lattices showing that the interplay between quadraticZeeman effect and spin-changing collisions may lead to various types of phases and phase transitions. I will then brieflycomment on how the spin-degree of freedom in high-spin lattice fermions may be employed to cool pseudo-spin-1/2fermions into the anti-ferromagnetic Neel ordering.


30

Probing non equilibrium physics in 1d quantum many body quantum systems byinterference

Jorg Schmiedmayer 1, ∗

1Vienna Center for Quantum Science and Technology (VCQ), Atominstitut, TU-Wien,Stadionallee 2, 1020 Vienna, Austria

The evolution of non-equilibrium many-body quantum systems is of fundamental importance. In this talk I willpresent our recent experiments studying the non equilibrium properties of 1d quantum many body systems. Interferingtwo 1 dimensional quantum gases allows to study how the coherence created between the two many body systems by thesplitting process [1] slowly dies by coupling to the many internal degrees of freedom available [2]. To reveal the natureof the fluctuations behind this decoherence we generalize the standard homodyne measurement of quantum optics tothe analysis of interference of two fluctuating quantum systems [3]. The full distribution function of the shot to shotvariation of the interference patterns leads a way to reveal the nature of the noise, and the non equilibrium quantumdynamics of the underlying processes [4]. Two distinct regimes are exposed: for short length scales the system ischaracterized by spin diffusion, for long length scales by spin decay. After a rapid evolution the distributions approacha steady state characterized by an effective temperature over eight times lower than the kinetic temperature of theinitial system. We associate this state with pre-thermalization.

This work was supported by the European Union integrated project AQUTE, the FWF and the Wittgenstein Prize.

[1] T. Schumm et al. Nature Physics, 1,57 (2005); S. Hofferberth et al. Nature Physics 2, 489 (2008).[2] S. Hofferberth et al. Nature 449, 324 (2007)[3] S. Hofferberth et al. Nature Physics 4, 489 (2008); HP Stimming et al. Phys. Rev. Lett. 105, 015301 (2010)[4] T. Kitagawa et al. Phys. Rev. Lett. 104, 255302 (2010).


31

A down-conversion source for twin-atom beams

T. Schumm, R. Bucker, J. Grond, S. Manz, T. Betz, A. Perrin, J. SchmiedmayerInstitute of Atomic and Subatomic Physics

Vienna University of Technology

Stadionallee 2, 1020 Vienna

e-mail: [email protected]

We use a one-dimensional quasi-BEC generated on an atom chip as a matter wave source for correlated atombeams, in analogy to an optical parametric amplifier. The source is pumped by a fully coherent population transferto a radial vibrational quantum state of the system. This is realized by applying an optimal control sequence, actingcontinuously on the centre of the trap. The excited state represents a highly non-equilibrium situation, which relaxestowards equilibrium (radial ground state) via a parity-conserving 2-atom collision process. Energy and momentumconservation lead to the production of back-to-back (k, -k) momentum correlated atom pairs. We analyze the temporaldynamics of this process and show that bosonic amplification is at work. Using a single-atom sensitive fluorescencedetector, we demonstrate close-to-perfect correlations in the twin-atom beams (-10 dB below shot noise). This newsource relies exclusively on external degrees of the atoms and can hence be transferred to any sufficiently controlledquantum system. We believe this source to enable a plethora of new investigations in the context of quantum-atom-optics with correlated particles.

32

Plasmonic nanopotentials for cold atoms

C. Stehle, H. Bender, D. Schmidt, C. Zimmermann, and S. SlamaPhysikalisches Institut

Eberhard-Karls Universitat Tubingen

Auf der Morgenstelle 14, D-72076 Tubingen


Surface Quantum Optics is an emerging field in physics which connects ultracold atoms with solid surfaces with theperspective to generate surface nanotraps for cold atoms and hybrid atom - solid state systems [1, 2]. Our particularinterest in this context are evanescent wave potentials which are enhanced by surface plasmon polaritons [3]. Thismethod allows us to tailor the transverse geometry of the evanescent field and generate complex dipole potentials ata submicron distance from the surface. For that, micro- and nanofabricated gold structures are integrated on thesurface of a prism and surface plasmons are excited in Kretschmann configuration. On one hand we use Bose-Einsteincondensates as a surface probe by measuring the surface plasmon resonance above several geometries. On the otherhand we demonstrate matter-wave diffraction of Bose-Einstein condensates from these structures which shows theirpossible application as matter-wave optical devices.

Keywords: cold atoms, surfaces, evanescent wave, surface plasmons, nanophysics

[1] H. Bender, P.Courteille, C. Zimmermann, and S. Slama, Appl. Phys. B 96, 275 (2009).[2] H. Bender, Ph.W. Courteille, C. Marzok, C. Zimmermann, and S. Slama, Phys. Rev. Lett. 104, 083201 (2010).[3] C. Stehle, H. Bender, F. Jessen, C. Zimmermann, and S. Slama, New J. Phys. 12, 083066 (2010).

33

Multiparticle Entanglement for Quantum Interferometry

Augusto Smerzi1

1INO CNR-BEC and Dipartimento di Fisica, Universita‘ di Trento, I-38050 Povo, Italy

The central goal of interferometry is to estimate a phase shift with the highest possible sensitivity. It has beenrecently shown that multiparticle entanglement is a resource for phase estimation with a sensitivity overcoming thestandard quantum (shot-noise) limit up to the ultimate Heisenberg bound. In this talk I discuss the interplay betweenmultiparticle entanglement and quantum interferometry in the context of a recent phase estimation experiment usingfour photonics q-bits.

34

Conditional Spin-Squeezing of a Large Ensemble via the Vacuum Rabi Splitting

J. K. Thompson,1, ∗ Z. Chen,1 J. G. Bohnet,1 S. Sankar,1 and Jiayan Dai1

1JILA, NIST, and Department of Physics, University of Colorado, 440 UCB, Boulder, CO 80309,USA

We demonstrate a collective quantum nondemolition measurement scheme that achieves sub-quantum projectionnoise sensitivity while preserving a high degree of coherence. The collective measurement prepares a conditionalspin-squeezed state with 3.4(6) dB enhancement in sensitivity below the standard quantum limit on quantum phaseestimation. The technique is demonstrated using a large ensemble of N = 7 × 105 87Rb atoms, with the psuedo-spin1/2 composed of the mF = 0 ground hyperfine clock states. The measurement relies on the strong collective couplingbetween the atomic ensemble and a low finesse cavity F = 710 to generate a vacuum Rabi splitting whose magnitudeencodes spin population information. This work emphasizes the critical role of the collective cooperativity parameterof cavity QED (equivalent to optical depth for free space experiments) for achieving coherence preserving quantumnon-demolition measurements.

x

z

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NRotateProbe

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lect

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6.8 GHz

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L = 2 cm

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umbe

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(106 )

0

FIG. 1: A series of collective spin population measurements allow the spin projection Jz to be determined below the quantumprojection noise level, whose magnitude is represented in cartoon (2) as a quasi-probability distribution of measurement out-comes. Coherence is preserved because the collective measurement avoids the determination of which specific of the N spins arein up or down. The measured value of the quantum fluctuation from the first measurement Jz1 can then be used to reduce thequantum noise in the second measurement Jz2, as might be done in a Ramsey measurement. Conceptually, this is equivalentto preparing a spin-squeezed state conditioned on the measurement outcome Jz1, as illustrated by cartoon (3).

∗Electronic address: [email protected]; URL: http://jila.colorado.edu/thompson

35

Mean field effects on the scattered atoms in condensate collisions

Marek Trippenbach,1, ∗ Jan Chwedenczuk,1 Pawe l Zin,1 and Piotr Deuar2

1Faculty of Physics, University of Warsaw, ul. Hoza 69, 00-681 Warsaw, Poland2Institute of Physics, Polish Academy of Sciences, Al. Lotnikw 32/46, 02-668 Warsaw, Poland

We consider the collision of two Bose Einstein condensates [1] at supersonic velocities and focus on the halo ofscattered atoms. This halo is the most important feature for experiments [2, 3] and is also an excellent testing groundfor various theoretical approaches. In particular we find that the typical reduced Bogoliubov description, commonlyused, is often not accurate in the region of parameters where experiments are performed. Surprisingly, besides thehalo pair creation terms, one should take into account the evolving mean field of the remaining condensate and on-condensate pair creation. We present examples where the difference is clearly seen, and where the reduced descriptionstill holds.

FIG. 1. Schematic representation of the BEC collision. (a) Geometry of the Bragg beams and level scheme of the 23S1–23P0 transition of 4He. A Bragg pulse of two polarized laser beams (shown by the two arrows) detuned by produces twocounterpropagating BECs that separate along their radial dimension at relative velocity 2v0. (b) Schematic diagram of thecollision geometry in the center-ofmass frame. The two disks represent the colliding condensates in momentum space. Thesphere represents the halo of scattered atoms. The cigar shaped initial condensate is shown in the center.

[1] Mean field effects on the scattered atoms in condensate collisions, P. Deuar, P. Zin, J. Chwedenczuk and M. Trippenbach,arxiv:1101.5533

[2] Observation of Atom Pairs in Spontaneous Four-Wave Mixing of Two Colliding Bose-Einstein Condensates, A. Perrin, H.Chang, V. Krachmalnicoff, M. Schellekens, D. Boiron, A. Aspect, and C. I. Westbrook, Phys. Rev. Lett. 99, 150405 (2007)

[3] Spontaneous Four-Wave Mixing of de BroglieWaves: Beyond Optics, V. Krachmalnicoff, J.-C. Jaskula, M. Bonneau, V.Leung, G. B. Partridge, D. Boiron, C. I. Westbrook, P. Deuar, P. Zin, M. Trippenbach, and K.V. Kheruntsyan, Phys. Rev.Lett. 104, 150402 (2010)

[4] Quantum Multimode Model of Elastic Scattering from Bose-Einstein Condensates, P. Zin, J. Chwedenczuk, A. Veitia, K.Rzazewski, and M. Trippenbach, Phys. Rev. Lett. 94, 200401 (2005)

[5] Simulation of a Single Collision of Two Bose-Einstein Condensates, J. Chwedenczuk, P. Zin, K. Rzazewski, and M. Trip-penbach, Phys. Rev. Lett. 97, 170404 (2006)

∗ [email protected]; http://www.fuw.edu.pl/˜matri

36

Molecule interferometry

H. Ulbricht,1, ∗ C. Szewc,1 and P. Venn1

1School of Physics and AstronomyUniversity of Southampton

Highfield, Southampton, SO17 1BJ, UKphone: ++44 (0)23 8059 2073

fax: ++44 (0)23 8059 3910

We will report on molecule interferometry experiments. The motivation for de Broglie interference of heavy par-ticles is both, the foundations of modern physics by investigating the quantum to classical transition and the use ofinterferometric techniques for applications as for example: molecule metrology, molecule sorting, molecule quantuminterference lithography and investigations of van der Walls/Casimir-Polder interactions. The center-of-mass inter-ferometry is not affected by internal excitation of the molecules as impressively demonstrated by our experiments. Ifhowever internal state dynamics is coupled to the center-of-mass motion by electric or optical fields, the interferencepattern is changed. We will explain our experiment on mapping the conformational change of hot molecules to itscenter of mass motion [1].

Cooling the motion and manipulation of complex particles to increase beam coherences and phase-space density anddecreasing speed is essential for future molecule interference experiments and we will illustrate ideas and preliminaryexperimental results for cooling and deceleration schemes for large particles. We will especially emphasize the statusof the development of the Southampton molecule interferometer [2].

[1] On the influence of the internal molecular dynamics on de Broglie interferometry,Gring, M., S. Gerlich, S. Eibenberger, S.Nimmrichter, T. Berrada, M. Arndt, H. Ulbricht, K. Hornberger, M. Mueri, M. Mayor, M. Boeckmann, N. Doltsinis, PhysRev A 81, 031604(R) (2010).

[2] A helical velocity selector for continuous molecular beams, Szewc, C., J. D. Collier, and H. Ulbricht, Rev. Sci. Instrum. 81,106107 (2010).

∗Electronic address: [email protected]; URL: http://www.phys.soton.ac.uk/matterwave/html/index.html

37

Atom imaging at the limits – taking pictures for matter-wave interferometry

M. Pappa,1 P.C. Condylis,1 M. Baker,1 D. Sahagun Sanchez,1

A. Lazoudis,1 G. Konstantinidis,1 O. Morizot,1 and W. von Klitzing1, ∗

1IESL–FORTHInstitute of Electronic Structure and Lasers,

Foundation of Research and Technology - Hellas,GR711 10, Heraklion Crete, Greece

Tel +30-2810-39-1546

Interferometry with massive particles offers an enormous increase in sensitivity and accuracy both for fundamentaland applied physics. One of the key aspects is the fact that the number of massive particles are preserved throughoutthe experiment. This can be exploited, for example, in Heisenberg limited detection, where the sensitivity scaleswith the number of particle as opposed to its square root. Fluorescence imaging offers single particle sensitivity[1]but usually requires the atom to be confined in a trapping potential. Recently, this technique has been extended toimages of atoms falling through a sheet of light.[2] Multichannel plates can be employed to detect single metastableatoms falling upon it.[3] However, a imaging technique which works in free-space has single-particle sensitivity is yetto be demonstrated.

Traditional absorption imaging offers very good resolution and easy of use. Unfortunately, due to technical noise itrarely reaches shot-noise limited performance. In this talk I will review the limits of traditional absorption imagingand then demonstrate diffractive dark ground imaging as an ultra-sensitive imaging technique capable imaging atomicensembles of tens of atoms with Fourier-limited spatial resolution. We demonstrate an improvement of an order ofmagnitude in sensitivity, when compared to absorption imaging, or time-resolution when compared to fluorescenceimaging.

FIG. 1: Dark-ground image of an atom cloud split via Stern-Gerlach separation into its different magnetic hyperfine states.From left to right: about 30 atoms in the the 〈f = 2,mf = −2〉 state, 58 atoms in the 〈f = 2,mf = −1〉 and 61 atoms in the〈f = 2,mf = 0〉 state. The 〈f = 2,mf = 1〉 and 〈f = 2,mf = 2〉 states are not populated. The clouds have a 1/e2 radius of5.5× 6µm. The exposure time was 100µs.

[1] Localized visible Ba+ mono-ion oscillator,W. Neuhauser, M. Hohenstatt, P. E. Toschek, and H. Dehmelt , Physical ReviewA (1980).

[2] Single-particle-sensitive imaging of freely propagating ultracold atoms, R. Bucker, A. Perrin, S. Manz, T. Betz, C. Koller, T.Plisson, J. Rottmann, T. Schumm, and J. Schmiedmayer , New Journal of Physics (2011).

[3] Hanbury Brown Twiss effect for ultracold quantum gases, M. Schellekens, R. Hoppeler, A. Perrin, J. V. Gomes, D. Boiron,A. Aspect, and C. I. Westbrook, Science (2005).

∗Electronic address: [email protected]; URL: http://www.bec.gr

38

Time-Resolved Observation of Coherent Multi-Body Interactionsin Quantum Phase Revivals

Sebastian Will,1, ∗ Thorsten Best,1 Simon Braun,1 Ulrich Schneider,1

Lucia Hackermuller,1 Dirk-Soren Luhmann,2 and Immanuel Bloch1

1Fakultat fur Physik, Ludwig-Maximilians-Universitat, 80799 Munchen, GermanyMax-Planck-Institut fur Quantenoptik, 85748 Garching, Germany

2Institut fur Laser-Physik, Universitat Hamburg, 22761 Hamburg, Germany

Interactions lie at the heart of correlated many-body quantum phases. Typically, the interactions between mi-croscopic particles are described as two-body interactions. However, also higher-order multi-body interactions cangenerally be present. In studies of Efimov physics, multi-body interactions have been observed as inelastic loss-resonances in three- and four-body recombinations of atoms and dimers.

In this talk, we report on the observation of effective coherent multi-body interactions among ultracold bosonicatoms on the sites of a three-dimensional optical lattice [1]. These interactions effectively emerge from two-bodycollisions, which can promote atoms from the ground state to higher-lying on-site orbitals. The admixture of theexcited orbitals alters the shape of the spatial wavefunction and gives rise to modified interaction energies as afunction of the atom number (see Fig. 1). In an effective field theory these modifications are identified with theemergence of higher-order multi-body interactions [2]. We have observed such interactions in time-resolved traces ofquantum phase revivals, using an atom interferometric technique to precisely measure the absolute energies of atomnumber states (Fock states) at a lattice site. The spectral content of the recorded time traces additionally revealsinformation on the atom number statistics at a lattice site, similar to foundational experiments in cavity quantumelectrodynamics that yield the statistics of a cavity photon field. Applying quantum phase revivals to mixtures ofbosonic and fermionic atoms, we have additionally been able to accurately measure the absolute strength of Bose-Fermi interactions as a function of the interspecies scattering length and observed the modification of Bose-Boseinteractions, mediated by an interacting fermion [3].

The accurate measurement of interaction energies enabled by quantum phase revival spectroscopy provides crucialinput for the comparison of optical lattice quantum simulators with many-body quantum theory. In future applica-tions, our technique can be used to reveal direct multi-body interactions, possibly present in the vicinity of Feshbachor Efimov resonances. The effective multi-body interactions demonstrated here may enable the quantum simulationof effective field theories, that are highly relevant to the description of atomic nuclei.

n = 2 n = 3 n = 4a b1

00 5 10

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ibili

ty

t (trev = h/U)

FIG. 1: Signature of multi-body interactions in quantum phase revivals. (a) Repulsive interactions broaden the ground-statewavefunction at a lattice site depending on the atom number n (orange solid lines) relative to the wavefunction in a non-interacting system (grey dashed lines). This gives rise to modifications of the Fock state energies, which are described byeffective multi-body interactions. (b) Quantum phase revivals of a coherent state of interacting bosons in the multi-orbitalsystem of a deep lattice well (blue solid line). The beat signal indicates coherent multi-body interactions.

[1] Time-resolved observation of coherent multi-body interactions in quantum phase revivals, S. Will, T. Best, U. Schneider,L. Hackermuller, D.-S. Luhmann, and I. Bloch, Nature 465 197 (2010).

[2] Effective three-body interactions of neutral bosons in optical lattices, P. R. Johnson, E. Tiesinga, J. V. Porto, andC. J. Williams, N. J. Phys. 11 093022 (2009).

[3] Coherent interaction of a single fermion with a small bosonic field, S. Will, T. Best, S. Braun, U. Schneider, and I. Bloch,arXiv:1011.3807v1 (2010).

∗Electronic address: [email protected]; URL: http://www.quantum-munich.de

39

Quantum Reflection of He2 Several Nanometers Above a Grating Surface

Bum Suk Zhao,1, ∗ Gerard Meijer,1 and Wieland Schollkopf1

1Fritz-Haber-Institut der Max-Planck-GesellschaftFaradayweg 4-6, 14195 Berlin, Germany

He2 is a fragile molecule with a binding energy of only 10−7 eV. At the given energy, the wave function describingthe internuclear motion extends far beyond the classically allowed range, which result in an extremely large bondlength (mean internuclear separation) of 5.2 nm (see Fig. 1(a)). As the probability for finding the atoms at a classicallyforbidden separation is more than 80%, He2 represents a frail giant quantum particle. Here, we report non-destructivequantum reflection of the helium dimer from a grating surface [1]. We scattered a beam containing dimers as wellas atomic helium and larger clusters, but could differentiate the dimer by its diffraction angle. Helium dimers arequantum reflected tens of nanometers above the surface where the surface-induced forces are too weak to dissociatethe fragile bond (Fig. 1(b)). Diffractive quantum reflection of the helium dimer represents an intriguing exampleof matter-wave optics, because it interconnects three fundamental quantum effects: (i) quantum reflection by anattractive interaction; (ii) diffraction of a particle by a periodic structure; and (iii) the internal quantum state of He2.

Internuclear separation R [Å]10 100

He-

He

pote

ntia

l [K]

-10

-5

0

5

10

15<R> = 52 Å

class. Rmax= 14 Å

(a)

He2

200

100

0

-100

He 2-s

urfa

ce p

oten

tial [

arb.

units

]

Height above surface z [nm]

1

10

(b) (c)

He+ -S

igna

l [10

3 cou

nts/

s]

0

1

2

3

4He2

Detection angle θ [mrad]0.0 0.5 1.0 1.5

x51

1

2

3

4

0

FIG. 1: Three basic examples representing principles of quantum mechanics. (a) The He-He interaction potential [2] (black)and the calculated probability function of 4He2 (red) as a function of internuclear separation. (b) Artistic view of quantumreflection of a helium dimer at the attractive van der Waals surface potential. (c) A diffraction pattern of a helium beamfor the stagnation pressure and temperature, 1 bar and 8.7 K, respectively, measured with the 4-amu mass channel of thedetector. (The dark trace represents a fivefold magnification of the intensity.) The calculated diffraction angles of He and He2are indicated by green dash-dotted and red solid lines, respectively, each labeled by the diffraction order number. The thindashed black line indicates the 0th-order (specular) peak position.

[1] Quantum Reflection of He2 Several Nanometers Above a Grating Surface, B.S. Zhao, G. Meijer, and W. Schollkopf, Science331, 892 (2011).

[2] Accurate analytical He-He van der Waals potential based on perturbation theory, K.T. Tang, J.P. Toennies, and C.L. Yiu,Phys. Rev. Lett. 74, 1546 (1995).

∗Electronic address: [email protected]; URL: http://www.fhi-berlin.mpg.de/mp/schoellkopf/

40

Causality in Condensates

W. H. Zurek1

1Theory Division, MS B213, LANL Los Alamos, NM, 87545, U.S.A.

Symmetry breaking during phase transitions can lead to the formation of topological defects (such as vortex lines insuperfluids). However, the usually studied BECs have the shape of a cigar, a geometry that impedes vortex formation,survival, and detection. I show that, in elongated traps, one can expect the formation of grey solitons (long-lived,non-topological phase defects) as a result of the same mechanism. Their number will rise approximately in proportionto the transition rate. This steep rise is due to the increasing size of the region of the BEC cigar where the phaseof the condensate wavefunction is chosen locally (rather than passed on from the already formed BEC). I will alsodiscuss buildup of the phase coherence in toroidal geometry, where it can result in the trapping of winding numbers.

41

Anisotropic 2D diffusive expansion of ultra-cold atoms in a disordered potential

B. Allard,1, ∗ T. Plisson,1 M. Robert-de-Saint-Vincent,1 J.-P. Brantut,1 L.Pezze,1 L. Sanchez-Palencia,1 A. Aspect,1 T. Bourdel,1 and P. Bouyer1

1Laboratoire Charles Fabry de l’Institut dOptique, Universite Paris Sud,CNRS, campus polytechnique RD128, 91127 Palaiseau France.†

Disorder is a ubiquitous feature in condensed matter physics. Recently, ultra-cold gases have allowed the study ofdisorder related phenomena thanks to their controllability and versatility [1]. Here, we present experimental resultson the horizontal expansion of an initially trapped 87Rb ultra-cold gas, vertically confined within a few quantumstates, in the presence of a speckle light field inducing anisotropic disorder [2].

We observe an anisotropic diffusive expansion for low energy atoms while the dynamic of high energy atoms remainsballistic and isotropic at our time scale (Fig.1). The density profiles are analysed to extract quantitative informationon the energy dependent diffusion coefficients [3] and compared with a model of classical diffusion. In agreement withnumerical simulations [4], the diffusion coefficients are found to be an algebraic function of the particule energy.

FIG. 1: Atomic column density after planar expansion of an ultra-cold gas in an anisotropic speckle potential. (a) Image after50ms of expansion. (b),(c) Integreted density along the two major axes after 50ms (plain dots) and 200ms(open squares) ofexpansion

Our system is a first step towards the exploration of disorder effects in 2D such as anomalous subdiffusion, classicaltrapping under the percolation threshold and Anderson localization [5]. Moreover, by cooling further our gas, we haveentered the superfluid regime and we may be able to study the effect of the disorder on the BKT transition.

[1] Disordered quantum gases under control, L. Sanchez-Palencia and M. Lewenstein, Nature Physics 6, 87 (2010).[2] Anisotropic 2D Diffusive Expansion of Ultracold Atoms in a Disordered Potential, M. Robert-de-Saint-Vincent, J.-P. Brantut,

B. Allard, T. Plisson, L. Pezze, L. Sanchez-Palencia, A. Aspect, T. Bourdel, and P. Bouyer, Pysical Review Letters 104,220602 (2010).

[3] Expansion of a Bose-Einstein Condensate in the Presence of Disorder, B. Shapiro, Physical Review Letters 99, 060602(2007).

[4] Diffusion of Cold Gases in Two-Dimensional Anisotropic Disorder L. Pezze et al., in preparation.[5] Localization of Matter Waves in Two-Dimensional Disordered Optical Potentials R. C. Kuhn, C. Miniatura, D. Delande,

O. Sigwarth and C. A. Muller, Physical Review Letters 95, 250403 (2005).

∗Electronic address: [email protected]†URL: http://www.atomoptic.fr/

42


C. Basler,1, ∗ F. Meinert,1 A. Lambrecht,1 and H. Helm1

1Department of Molecular and Optical Physics, Physikalisches Institut, Uni-FreiburgStefan-Meier-Str. 19 VF, 79104 Freiburg, Germany

Tel (+49)(0)761 203 7636

A table-top atomic clock based on coherent population trapping (CPT) resonances with parallel linearly polarizedoptical fields in a vapor cell has recently been demonstrated on the D1 line of 87Rb[1]. We study this transition withcounter-propagating laser beams in an optical dipole trap. One goal is to explore the suitability of this transition foran all optical path to continuous generation of low temperature trapped atom samples using the proposed EIT-coolingscheme [2,3]. Due to the low trapping frequencies which can be realized for neutral atoms, a magnetic-field insensitiveCPT resonance transition appears paramount to success. A second attractive feature of this transition is the highcontrast of the resonance amplitude[1]. The experiment is carried out using two externally phase-locked diode lasersand a crossed CO2 laser dipole trap which is loaded from a 2D-MOT.Research supported by DFG HE2525/7

[1] E. E. Mikhailov et al.[2] C. Morigi, Phys. Rev. A. 67 033402 (2003) (2011).[3] M. Roghani et al., Phys. Rev. A 81 033418 (2010)

∗Electronic address: [email protected]; URL: http://frhewww.physik.uni-freiburg.de/

43

Two-point phase correlations of a one-dimensional bosonic Josephson junction

T. Betz,1 S. Manz,1 R. Bcker,1 T. Berrada,1 G. Kazakov,1 I. E. Mazets,1

H.-P. Stimming,1 A. Perrin,1 T. Schumm,1 and J. Schmiedmayer1

1Faculty of PhysicsUniversity of Vienna

Boltzmanngasse 5, 1090 Vienna

We realize a one-dimensional Josephson junction using quantum degenerate Bose gases in a tunable double wellpotential on an atom chip. Matter wave interferometry gives direct access to the relative phase field, which reflectsthe interplay of thermally driven fluctuations and phase locking due to tunneling. The thermal equilibrium state ischaracterized by probing the full statistical distribution function of the two-point phase correlation. Comparison toa stochastic model allows us to measure the coupling strength and temperature and hence a full characterization ofthe system.

44

Detecting the amplitude mode by Bragg spectroscopy in strongly correlated latticebosons

U. Bissbort1, ∗ and M. Buchhold1

1Institut fur Theoretische Physik, Johann Wolfgang Goethe-Universitat, 60438 Frankfurt/Main, Germany

We report the first detection of the Higgs-type amplitude mode using Bragg spectroscopy in a strongly interactingcondensate of ultracold atoms in an optical lattice. By the comparison of our experimental data with a spatiallyresolved, time-dependent dynamic Gutzwiller calculation, we obtain good quantitative agreement. This allows for aclear identification of the amplitude mode, showing that it can be detected with full momentum resolution by goingbeyond the linear response regime. A systematic shift of the sound and amplitude modes? Resonance frequencies dueto the finite Bragg beam intensity is observed.


45

Interference patterns of laser-dressed states in a supersonic atomic/molecular beam

M. Bruvelis,1, ∗ A. Ekers,1 J. Ulmanis,1 K. Miculis,1 N. N. Bezuglov,2 and C. Andreeva3

1Laser Centre, University of Latvia, LV-1002, Riga, Latvia2Faculty of Physics, St. Petersburg State University, 198904 St. Petersburg, Russia

3Institute of Electronics, Bulgarian Academy of Sciences, Sofia 1784, Bulgaria

Interference of laser-dressed states can be observed when light-induced crossings of energy levels enable the popu-lation to split between distinct excitation pathways that recombine afterwards. In this poster we present observationand interpretation of such interference patterns obtained in a Ramsey-type experiment in a supersonic Na/Na2atomic/molecular beam[1]. The excitation pathways are generated by applying two laser fields in an open three levelladder system g-e-f as seen in Fig. 1. In the experiment, the dressed states are spatially varying the two lasers arecw and cross a supersonic sodium beam, coupling the g-e-f ladder. The lasers are focused in such a way that a strongand short (tightly focused) pump laser couples the two lower levels g and e , and weak and long (less tightly focused)probe laser couples the intermediate level e and the upper level f. The energy difference between the dressed statesis determined by the pump field Rabi frequency and its detuning off from resonance. This particular arrangementproduces the excitation spectra of level f consisting of oscillatory patterns with distinct maxima and minima that arecharacteristic to interference patterns. Detailed numerical calculations based on the dressed-state picture show thatthis particular arrangement of dressing fields can be used to vary the spatial distribution of highly excited atoms,which can be precisely controlled by varying the frequencies and intensities of both laser fields.

corelates to state

corelates to state

corelates to stateS

PS

P

time (a.u.)

population can evolve through two pathways

phase dependent intefrerence can happen when pathways cross for the second time

Laser Rabi frequency

(a.u)

FIG. 1: Excitation in an open three level ladder system g-e-f.

[1] Consequences of optical pumping and interference for excitation spectra in a coherently driven molecular ladder system,Bezuglov, N. N., Garcia-Fernandez, R., Ekers, A., Miculis, K., Yatsenko, L. P. and Bergmann, K., Phys. Rev. A 78, 053804(2008).

∗Electronic address: [email protected]; URL: http://www.google.com/profiles/martins.bruvelis

46

Creating exotic condensates through the interplay of quantum phase revival and trapdynamics

M. Buchhold,1, ∗ U. Bissbort,1 S. Will,2, 3 and W. Hofstetter1

1Institut fur Theoretische Physik, Johann Wolfgang Goethe UniversitatMax-von-Laue-Str. 1 , 60438 Frankfurt am Main, Germany

Tel +49 69 798-47823, Fax +49 69 798-478812Fakultat fur Physik, Ludwig-Maximilians-Universitat, 80799 Munchen, Germany

3Max-Planck-Institut fur Quantenoptik, 85748 Garching, Germany

In the field of ultracold atoms in optical lattices a plethora of phenomena governed by the hopping energy J andthe interaction energy U have been studied in recent years. However, the trapping potential typically present inthese systems sets another energy scale and the effects of the corresponding time scale on the quantum dynamicshave rarely been considered. Here we study the quantum collapse and revival of a lattice Bose-Einstein condensate(BEC) in an arbitrary spatial potential, focusing on the case of harmonic confinement. Analyzing the time evolutionof the single particle density matrix, we show that the physics arising at the (temporally) recurrent quantum phaserevivals is essentially captured by an effective single particle theory. The resulting dynamics enables several potentialapplications: First, a precise measurement of the harmonic trapping potential underlying the lattice system by usingthe momentum density n(k). Second, monitoring mechanical or thermal drifts of the harmonic potential relativeto the lattice sites with a resolution of a small fraction of the lattice spacing, and, third, the preparation of exotic,non-equilibrium condensate states.

∗Electronic address: [email protected]; URL: http://itp.uni-frankfurt.de/cms/index.php?id=buchhold

47

Phase estimation with interfering Bose-Einstein-condensed atomic clouds

Jan Chwedenczuk,1, ∗ Francesco Piazza,2 and Augusto Smerzi2

1Faculty of Physics, University of Warsaw, ul. Hoza 69, 00-681 Warsaw, Poland2BEC Center, Dipartimento di Fisica, Universita di Trento, Via Sommarive 14, I-38123 Povo, Italy

We study the measurement of the position of atoms as a means to estimate the relative phase between two Bose-Einstein condensates. We consider N atoms released from a double-well trap, forming an interference pattern, with arelative phase θ among them, as shown in Fig.1. We show that a simple least-squares fit to the density gives a shot-noise limited sensitivity. The shot-noise limit can instead be overcome by using correlation functions of order

√N or

larger. The measurement of the Nth-order correlation function allows to estimate the relative phase at the Heisenberglimit with a proper choice of the initial state of the two-well BEC. Phase estimation through the measurement of thecenter-of-mass of the interference pattern can also provide sub-shot-noise sensitivity. Yet, the implementation of bothprotocols might be experimentally difficult. These results indicate that the achievement of sub shot-noise sensitivityusing the interference pattern might prove challenging.

FIG. 1. Schematic representation of the interferometric procedure. First, a relative phase θ is imprinted between the wells.Then, the BECs are released from the trap and form an interference pattern. The detectors (symbolically represented as opensquares) measure the positions of atoms and this data is a starting point for the phase estimation.

[1] Phase estimation with interfering Bose-Einstein-condensed atomic clouds, J. Chwedenczuk, F. Piazza and A. Smerzi, Phys.Rev. A 82, 051601(R) (2010)

[2] Phase Estimation from Atom Position Measurements, J. Chwedenczuk, F. Piazza and A. Smerzi, arxiv:1012.3593

∗ [email protected]

48

Measuring Energy Differences by BEC Interferometry on a Chip

J. P. Cotter,1, ∗ B. Yuen,1 Florian Baumgartner,1 R. J. Sewell,1

S. Eriksson,1 I. Llorente-Garcia,1 Jos Dingjan,1 and E. A. Hinds1

1Centre for Cold Matter, Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2AZ, UK

We investigate the use of a Bose-Einstein condensate trapped on an atom chip for making interferometric measure-ments of small energy differences[1, 2]. A nearly pure condensate of 1.5× 104 atoms is split horizontally by a distanceL using an rf magnetic field[3]. We introduce a relative height difference ∆y between the clouds by uniformly rotatingthem over a time τ/2 by adjusting the rf field[4]. The trap is turned off allowing the clouds to interfere in free fall. Forvarying height separations we measure the relative phase difference φ between the clouds from the observed fringesin the atomic density distribution, obtaining an energy difference of 6.61(11) Hz/nm.

Λ

chip substrate

gold wires

bias field Bx

rf field

dc trapping field

x

y

Δy

L

μ2

μ1

108 mm

-150 -100 -50 0 50 100 150

-5

0

5

Dy HnmL

Φ�HΤ

�2L

Hrad�

msL

FIG. 1: (Left) Gold wires on the atom chip carry dc and rf currents that, together with a bias field, form a static magnetictrap. The rf field splits the condensate and allows the double trap to be rotated. Gravity acts along the y axis. A single-shotabsorption image of the interfering clouds is shown. (Right) Interferometer phase φ versus height difference ∆y, where φ hasbeen divided by τ/2 to correct for phase spreading. We obtain an energy difference of 6.61(11) Hz/nm.

We measure and explain the noise in the energy difference of the split condensates, which derives from the binomialdistribution in the number difference. We also consider systematic errors. A leading effect is the variation of rfmagnetic field in the trap with distance from the wires on the chip surface. This can produce energy differencescomparable with those due to gravity. After correcting for systematics we measure an energy difference of 2.17(32)Hz/nm as expected from Earth’s gravity.

The small size of the atom cloud and its close proximity to a surface make BEC interferometry on a chip attractivefor mapping atom-surface interactions. Over the range of a few microns from the surface it should be possible tomake measurements with ∼ 1% accuracy. This offers the possibility of improving over the existing measurements ofthe Casimir-Polder interaction and its temperature dependance[5–7].

[1] Atom chip for BEC interferometry, R. J. Sewell, et. al., J. Phys. B (2010).[2] Measuring Energy Differences by BEC Interferometry on a Chip, F. Baumgartner, et. al., Phys. Rev. Lett. (2010).[3] Two-Dimensional Atom Trapping in Field-Induced Adiabatic Potentials, O. Zobay and B. Garraway, Phys. Rev. Lett. (2001).[4] Radiofrequency-dressed-state potentials for neutral atoms, S. Hofferberth, I. Lesanovsky, et. al., Nature Physics (2006).[5] Measurement of the Casimir-Polder force, C. I. Sukenik, et. al., Phys. Rev. Lett. (1993)[6] Measurement of the Casimir-Polder force through center-of-mass oscillations of a Bose-Einstein condensate, D. M. Harber,

et. al., Phys. Rev. A (2005).[7] Measurement of the Temperature Dependence of the Casimir-Polder Force, J. M. Obrecht, et. al., Phys. Rev. Lett., (2007)

∗Electronic address: [email protected]; URL: http://www3.imperial.ac.uk/ccm/

49

Metrology with rotating matter waves

Jacob Dunningham,1 David Hallwood,1 Jessica Cooper,1 and Luis Rico Gutierrez1

1School of Astronomy and PhysicsUniversity of Leeds

Woodhouse Lane, Leeds LS2 9JT

A promising practical application of entanglement is metrology, where quantum states can be used to make mea-surements beyond the shot noise limit. Recent experiments have demonstrated this improvement using atomic Bose-Einstein condensates[1]. I will consider the case of a condensate trapped in a ring-shaped potential, which is stirred[2].At critical stirring rates, the condensate undergoes a quantum phase transition characterized by large-scale entan-glement spreading across the system. The simple process of stirring can generate interesting quantum states suchas macroscopic superpositions of all the atoms flowing in opposite directions around the ring. I will show how thissystem could be used to realize a quantum-limited gyroscope and will consider how it can be optimized to accountfor decoherence. Finally, by considering lower dimensional systems, I will discuss relatively straightforward methodsfor generating quantum states that are ideally suited to this scheme[3].

[1] C. Gross, T. Zibold, E. Nicklas, J. Esteve, and M.K. Oberthaler, Nature 464, 1165 (2010)[2] J.J. Cooper, D.W. Hallwood, and J.A. Dunningham, Phys. Rev. A 81, 043624 (2010)[3] D. Dagnino, N. Barberan, M. Lewenstein, and J. Dalibard, Nature Physics 5, 431 (2009).

50

Penning ionization of two ultracold Rydberg atoms

D.Efimov,1, ∗ N.Bezuglov,1 and A.Ekers2

1Faculty of Physics, St.Petersburg State University, 198904 St. Petersburg, RussiaTel +7 812 428-7200, Fax +7 812 428-7240

2Laser Centre, University of Latvia, LV-1002 Riga, Latvia

The ionization dynamics of cold Rydberg gases plays an important role in the evolution of cold plasma observed incold matter [1]. Free electron escaping in collisions of two Rydberg atoms is possible via two mechanisms: associativeand Penning ionization. Associative ionization is a short range process and needs overlapping the both valenceelectrons wave functions. Penning ionization is a long-range process and may occur with atoms well space separatedat antinuclear distances R� n2 (where n, n are the effective and principal quantum numbers -atomic units are used).

We consider coupling between two ultrocold Hydrogen Rydberg atoms using model of dipole-dipole interaction.It’s supposed that Auger process takes place: while the first atom moves down from (ndld) to (n′dl

′d), the second one

ionizes from (nili) to (pil′i) states with energies ωi = ωd = 1/2(n′d)−2 − 1/2(nd)−2, ωd = 1/2(ni)

−2 + p2i /2. A simple

asymptotic expression of the autoionization width Γ [1] for the above process has been obtained from semiclassicalformulas presented in [2]:

Γ ' 3(2ld + 1)

πn3dn3iR

6

Γ4( 23 )

Γ( 43 )

[3

17

(1

2(nd − 1)2− 1

2n2d

)− 173

+

(1

2nd2 −

1

2n2d

)− 203

]. (1)

Here nd is the principal quantum number of the nearest lower level to a virtual level which effective quantum numbern∗d meets the requirement n∗−2d = n−2i + n−2d . Importantly, an interesting counterintuintive phenomena is predictedwith our results: the decreasing of the principal quantum number nd of the unionized atom (i.e. the decreasing of itssize) results in an essential jump of the ionization efficiency (see Fig. 1).

1020

3040

50

1020

3040

500

20000

40000

60000

nd

R

6 , ar

bit.

un.

n i

FIG. 1: Autoionization width of two Hydrogen Rydberg atoms with the orbital quantum numbers li = ld = 1.

Support by the EU FP7 IRSES Project COLIMA is acknowledged.

[1] Autoionization of an ultracold Rydberg gas through resonant dipole coupling, T.Amthor, J.Denskat, C.Giese, N.N.Bezuglovat al, Eur. Phys. J. D 53, 329 (2009)

[2] Generalised correspondence rules for quasi-classical dipole matrix elements, N.N.Bezuglov, V.M.Borodin, Optics and Spec-trosc. 86, 467 (1999)


51

Giant coherence time due to spin self-rephasing in an optical trap

G. Kleine Buning1, J. Will1, W. Ertmer1,∗ E. Rasel1, J. Arlt2, and C. Klempt11 Institut fur Quantenoptik, Leibniz Universitat Hannover, Welfengarten 1, 30167 Hannover, Germany and2 Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark

F. Ramirez-Martinez3, F. Piechon4, and P. Rosenbusch3

3LNE-SYRTE, Observatoire de Paris, 61 av de l’Observatoire, 75014 Paris, France and4Laboratoire de Physique des Solides, CNRS UMR 8502, Univ. Paris-Sud, 91405 Orsay, France

The definition of the second is provided by microwave fountain clocks. Besides the quest for highest accuracy,applications ranging from navigation to communication technology demand more stable and compact atomic frequencystandards. The stability of all interferometric clocks is limited by the duty cycle, the ratio between interrogation andcycle time. The interrogation time of fountain clocks is limited by their principle of operation, preventing a compactrealization. This limitation could be overcome by using trapped atomic ensembles instead of fountains.

However, in a trapped ensemble the confining potential is generally different for the two states defining the clocktransition. This results in a differential frequency shift which is necessarily inhomogeneous across the trapped ensem-ble. Hence, the atoms experience a slightly different phase evolution in each trap state. This dephasing mechanismleads to a loss of contrast of the interferometer signal and thus limits the interrogation time. In a special magneticconfinement, for which the inhomogeneity of the Zeeman shift is canceled by the density shift, it was shown thatthe collisional interaction can be used to induce spin self-rephasing [1]. This effect inhibits dephasing and inducescharacteristic contrast revivals, mediated by collisional interaction.

We show that spin self-rephasing is applicable in an optical potential for the magnetically insensitive clock states.We demonstrate a coherence time of 21 s – the longest ensemble coherence time measured so far (see Fig. 1). Thecoherence time is achieved in a Ramsey sequence on the 87Rb hyperfine transition, a secondary representation of thesecond. We show that both the inhomogeneity of the differential light shift and the inhomogeneity of the density shiftcan be overcome by spin self-rephasing. Furthermore, we evaluate the applicability of spin self-rephasing for atomicmicrowave clocks and demonstrate a stability of 2.4 × 10−11 at one second, which is limited by technical noise. Wepredict a 300 fold stability enhancement for a purpose-built apparatus with standard technical improvements, whichenters the stability range of most atomic fountain clocks in a potentially much more compact setup. Our findings provethe fundamental nature of spin self-rephasing which is independent of the type of trap and the magnetic quantumnumber. Thus, its applicability might be extended to optical lattice clocks as well as quantum information withatomic ensembles.

0 5 1 0 1 5 2 0 2 5 3 0 3 50 . 0

0 . 5

1 . 0

0 . 0 0 . 5 1 . 0 1 . 50

1

Popu

lation

transf

er P

I n t e r r o g a t i o n t i m e ( s )

FIG. 1: Ramsey sequence with spin self-rephasing. Due to frequency noise, the Ramsey fringes wash out after some seconds ofinterrogation time (see inset for the first 1.5 s). However, the contrast of the population transfer P is well visible. It reaches1/e at 21 s and vanishes completely after 26 s. The solid line represents a solution of a numeric model.

[1] C. Deutsch et al., Phys. Rev. Lett. 105, 020401 (2010).

∗Electronic address: [email protected]; URL: http://www.iqo.uni-hannover.de

52

A ring trap for matter-wave interferometry

B. E. Sherlock,1, ∗ M. Gildemeister,1 E. Owen,1 E. Nugent,1 and C. J. Foot1

1Clarendon LaboratoryParks Road, Oxford, OX1 3PU, United Kingdom

Tel +44 1865 282201

We present experimental data on a novel ring trap with smoothly adjustable radius and a lifetime well suited tocold atom experiments. The toroidal geometry is generated by the application of an oscillating magnetic bias fieldto a radio-frequency (rf) dressed quadrupole trap. The result is a Time-Averaged Adiabatic Potential (TAAP)[1][2]with an annular minimum, the radius of which can be dynamically varied from 50µm to 250µm. Control over the ringradius allows the trap two be operated in two distinct regimes. For large ring radii the trap forms a smooth circularwaveguide with notable advantages for matterwave interferometry such as a large enclosed area and the absence ofa net magnetic moment due to the atoms being trapped in a balanced superposition of Zeeman substates. For ringradii < 60µm the quantum coherence fills the ring presenting an opportunity to study the superfluid properties of adilute ultracold quantum gas.

The ring trap is conveniently loaded from a conventional time-averaged orbiting potential trap, with minimalheating and atom loss. We have measured oscillation frequencies of atoms in the potential which present goodagreement with our theoretical model. Refinements to the ring geometry can be achieved via controlled adjustmentsto the polarisation of the rf dressing field. Correction for gravitational asymmetries and a rotation scheme have beenimplemented following this method. A Bose-Einstein condensate has been loaded into the large ring configurationand its motion around the ring has been observed.

[1] Time-Averaged Adiabatic Potentials: Versatile Matter-Wave Guides and Atom Traps, Igor Lesanovsky and Wolf von Klitz-ing, Phys. Rev. Lett. 99, 083001 (2007).

[2] Trapping ultracold atoms in a time-averaged adiabatic potential, M. Gildemeister, E. Nugent, B. E. Sherlock, M. Kubasik,B. T. Sheard and C. J. Foot, Phys. Rev. A 81, 031402(R) (2010).

∗Electronic address: [email protected]; URL: http://www-matterwave.physics.ox.ac.uk/

53

Multispecies kinetic theory of cavity-mediated cooling and selforganisation

T. Grießer,1, ∗ W. Niedenzu,1 and H. Ritsch1

1Institut fur Theoretische Physik, Universitat InnsbruckTechnikerstraße 25, 6020 Innsbruck, Austria

We present a kinetic theory of several different species of polarisable particles in a transversally-pumpedhigh-Q standing-wave resonator. Within the framework of Vlasov theory (continuous phase space distributionfor large particle numbers [1]) we determine the instability condition for the homogeneous phase for a fixed setof velocity distributions of the various types of particles. Whereas for a single species the ratio of potential- tokinetic energy needs to be bounded for stability to prevail, in the many-species case it is the sum of the individualratios which has to satisfy this very bound. Therefore, instability is the easier to achieve the more species are involved.

Neglecting statistical fluctuations as well as the field mode input noise, Vlasov’s equations allow for an infinitenumber of stable solutions, no matter whether homogeneous or selforganised. As a remedy to this unphysical degen-eracy we include ∼ 1/N corrections to obtain selfconsistent, coupled nonlinear Fokker-Planck equations for the phasespace distributions of the different species. Their most general equilibrium solution below instability threshold is theq-Gaussian distribution (also called Tsallis distribution), leading e. g. to the Gaussian or the Lorentzian velocity dis-tributions as special cases. The final temperature reached by cavity cooling is limited by half of the cavity linewidth,giving us a dissipation-induced selforganisation condition. If the latter is satisfied, the selforganised phase is reachedeven if the ensembles are initially stable and the final temperature is modified by the trap frequency.

[1] A Vlasov approach to bunching and selfordering of particles in optical resonators, T. Grießer, H. Ritsch, M. Hemmerling,and G. R. M. Robb, Eur. Phys. J. D 58, 349 (2010).


54

Bright matter-wave solitons: Formation, dynamics and quantum reflection

Sylvi Handel,1, ∗ A. L. Marchant,1 T. P. Wiles,1 S. A. Hopkins,1 and S. L. Cornish1

1Department of Physics, Durham University, Durham DH1 3LE, United Kingdom

Bose-Einstein condensates in 1D can support both dark (local minima in the wave function) and bright (localmaxima) solitons depending on whether the interactions are repulsive or attractive, respectively. Previously, we havedemonstrated that a robust configuration of multiple solitons is created during the collapse of 85Rb condensates [1].Confined in a cylindrically symmetric trap, the solitons were observed to oscillate along the weaker axial directionrepeatedly colliding in the trap centre. Detailed analysis of binary soliton collisions using the Gross-Pitaevaskiiequation (GPE) shows that the stability of these collisions depend critically on the relative phase and velocity of thesolitons [2]. Moreover, the GPE results suggest that the solitons must form with a relative phase of p to ensure theirobserved stability [2]. However, new theoretical work suggests that the inclusion of quantum fluctuations causes thesoliton dynamics to be predominantly repulsive in 1D independent of their initial relative phase [3]. We report thedevelopment of a new apparatus designed to resolve this question and to explore the application of solitons in atominterferometry and precision measurement through the study of atom-surface interactions and quantum reflection.

[1] Formation of Bright Matter-Wave Solitons during the Collapse of Attractive Bose-Einstein Condensates, Cornish S. L. andThompson S. T. and Wieman C. E., Phys. Rev. Lett. 96, 170401 (2000).

[2] Collisions of bright solitary matter waves, Parker N. G. and Martin A. M. and Cornish S. L. and Adams C. S., J. Phys. B.41, 045303 (2008).

[3] Dynamical formation and interaction of bright solitary waves and solitons in the collapse of Bose-Einstein condensates withattractive interactions, Dabrowska-Wuster B. J. and Wuster S. and Davis M. J., New J. Phys. 11, 053017 (2009).

∗Electronic address: [email protected]; URL: massey.dur.ac.uk

55

Weak (anti-)localization of Bose-Einstein condensates in two-dimensional chaoticcavities

Timo Hartmann,1, ∗ Juan Diego Urbina,1 Klaus Richter,1 and Peter Schlagheck2

1 Institut I Theoretische Physik, Universitat RegensburgUniversitatsstraße 31, D-93053 Regensburg, Germany

2Departement de Physique, Universite de Liege, 4000 Liege, Belgium

The possibility to induce artificial magnetic gauge potentials for matter waves [1] and to create almost arbitrarilyshaped confinement potentials [2] makes it now interesting and feasible to study coherent transport of Bose-Einsteincondensates through various mesoscopic structures. Previous theoretical studies have focused on the question howcoherent backscattering in disordered potentials is modified by the presence of the atom-atom interaction [3]. Wenow study the analogous scenario of weak localisation in ballistic billiard geometries which exhibit chaotic classicaldynamics [4]. To this end we numerically investigate the quasi-stationary propagation of a condensate through suchstructures within the mean-field approximation.

The reflection is measured as a function of the magnetic gauge field and of the strength g of the non-linearity asshown in Fig. 1. With increasing non-linearity an inversion of the weak-localisation peak is visible and its origin willbe discussed.

0.0010 0.0005 0.0000 0.0005 0.0010

effective gauge field

0.10

0.12

0.14

0.16

Reflect

ion into

t

he s

am

e c

hannel

g=0.000g=0.005g=0.010g=0.015g=0.020g=0.025g=0.030g=0.035

FIG. 1: The channel resolved reflection is measured as a function of the magnetic gauge field for various values of the non-linearity g. The points show the results of the numerical simulations while the solid lines show the prediction from a semiclassicalanalysis. For the linear case g = 0 we see the Lorentz shape of the weak-localisation peak which gets deformed in a characteristicway for g 6= 0.

[1] Bose-Einstein Condensate in a Uniform Light-Induced Vector Potential, Y.-J. Lin et al., Phys. Rev. Lett. 102 130401 (2009)[2] Experimental demonstration of painting arbitrary and dynamic potentials for BoseEinstein condensates, K. Henderson et

al., New J. Phys. 11, 043030(2009)[3] Coherent Backscattering of Bose-Einstein Condensates in Two-Dimensional Disorder Potentials, M. Hartung et al., Phys.

Rev. Lett. 101, 020603 (2008)[4] Semiclassical Theory of Chaotic Quantum Transport, Klaus Richter and Martin Sieber, Phys. Rev. Lett. 89, 206801 (2002)


56

Correlated phonon scattering in mesoscopic Silicon Nanowires

Kedar Hippalgaonkar,1 Renkun Chen,1 and Arun Majumdar1

1University of California4164 Etcheverry Hall

We intend to investigate thermal transport in ultrathin Silicon Nanowires with random rough edges and/or bulkdisorder to expand fundamental understanding of phonon propagation in high quality single crystalline systems. In1958, Philip Anderson predicted localization of extended electron wavefunctions in disordered crystals resulting inexponentially decaying tails1. Conductivity was hypothesized to deviate from diffusive behavior and decay exponen-tially. This ubiquitous wave physics has since been demonstrated experimentally for light waves, microwaves, soundwaves, electron gases, and matter waves.

Phonons, although defined as quantized lattice waves in a solid, have always been pictured as particles movingdiffusively in a solid. While phonon-boundary, phonon-phonon and electron-phonon interactions have been studied indetail, they are sufficiently understood by energy and crystal momentum conservation laws governing the scatteringof particles. In these cases, phonons are incoherent and exhibit no wavelike behavior. However, at low temperatures(∼ 1− 100 K) and in the presence of disorder, coherent effects can be observed. One example is interference betweenmultiple scattering paths resulting in localization, although direct observation of such spatial confinement has neverbeen demonstrated, partly because phonons are broadband and interactions in solids are strong. In collaboration withProf. Joel Moores group in UC Berkeley, Physics Department, we predict an exponential reduction in the conductivityas a function of length, which would be the first such demonstration of localized phonons.

We intend to manufacture Silicon Nanowires that are 2-100nm in length, 10-20nm in width, and 10-20nm inthickness, patterned with High Resolution E-Beam Lithography (EBL) in the Molecular Foundry. In previous workcollaborating with Prof. Peidong Yang in the Chemistry Department, we have demonstrated that rough siliconnanowires synthesized by the aqueous electroless etching method have much lower thermal conductivity ( 1.6 W/m-Kfor a 50nm diameter NW at 300K) compared to that of smooth Si NWs grown by vapor-liquid-solid method. Thisis approaching thermal conductivity shown by amorphous Silicon ( 1 W/m-K) and is due to the enhanced phononscattering at rough nanowire surfaces [1]. We hypothesize that the exact mechanism of this phonon scattering couldbe due to Anderson Localization of lattice vibrational waves as described above and this careful proposed work willthrow light on the unique mechanism. We have developed an integrated thermal measurement technique to allowaccurate and sensitive thermal conductance of suspended nanowires in preparation for this work [2].

[1] Hochbaum, A. I. et al. Enhanced thermoelectric performance of rough silicon nanowires, Nature 451, 163-165, (2008)[2] Hippalgaonkar, K. et. al. Nano Letters, 10 (11), 4341 (2010)

57

Continuous approach to cold atom interferometers

A. Joyet,1, ∗ L. Devenoges,1 G. Di Domenico,1 and P. Thomann1

1Laboratoire Temps - Frequence (LTF), University of NeuchatelAv. de Bellevaux 51, 2009 Neuchatel, Switzerland

Matter-wave interferometers using cold neutral atoms can be used to realize precision measurements of variousphysical quantities. Nowadays these instruments are based on a sequential mode of operation. Atoms are firstprepared in a defined quantum state, then optically interrogated and finally detected before a new sequence startsagain. This kind of operation may suffer from a degradation of the measurement stability due to dead times (Dickeffect) which is well known in pulsed atomic fountain clocks for example.

In the case of fountain clocks, we have shown that a continuous mode of operation allows one to keep the stabilitydegradation to a negligible level compared to the shot-noise limited stability [1]. From that point of view, a continuousapproach to cold atom interferometers could be advantageous to improve their ultimate sensitivity as shown in ourtheoretical analysis of the aliasing noise in a cold atom gyroscope [2]. Moreover, to implement such an approach, thenecessary components developed for our continuous fountain clocks could also be useful to cold atom interferometers.

The first component is the source of the continuous cold and slow atomic beam. It consists of a 3D-optical molasses,loaded by an efficient continuous 2D-MOT pre-source [3], that provides a slow (adjustable velocity of a few m/s) andcold (70µK) continuous beam with a high atomic flux (1010 at/s).

The second component, located at the output of the optical molasses, is a transverse laser cooling stage whichrealizes an efficient collimation of the atomic beam. It is achieved with a 2D-optical lattice perpendicular to theatomic beam that uses Sisyphus cooling to reduce the transverse temperature down to 4µK.

Then, quantum state preparation of the atoms is the next component that follows the collimation stage. It combinestwo-laser optical pumping with Sisyphus cooling to avoid reheating of the atoms. Laser cooling is achieved withinanother 2D-optical lattice superposed to a Zeeman pumping laser that puts the atoms in the F = 3,m = 0 state [4].

The last and key component is specific to a continuous approach. With the use of a continuous beam, light emittedfrom the source can reach the region where the atoms are interrogated and thus perturbs the measurement. To avoidthat, we have developed a rotating light-trap, located after the state preparation stage, that removes the light fromthe atomic beam. It is composed of an electrostatic motor that drives a turbine whose blades are made of absorbingglass [5].

In this contribution, we will give an overview of the above mentioned elements which are required in a continuousapproach, as well as a first quantitative analysis of the potential improvement in sensitivity that can be expected fora cold atom gyroscope.

[1] J. Guena, G. Dudle, and P. Thomann, Eur. Phys. J. Appl. Phys. 388, 183-189 (2007).[2] A. Joyet, et al., To be published.[3] N. Castagna, et al., Eur. Phys. J. Appl. Phys. 34, 21-30 (2006).[4] G. Di Domenico, et al., PRA 82, 053417 (2010).[5] F. Fuzesi, et al., Rev. Sci. Instrum. 78, 103109 (2007).

∗Electronic address: [email protected]; URL: http://www2.unine.ch/ltf

58

Blue/Red Superradiance Threshold Asymmetry

N. S. Kampel,1, ∗ A. Griesmaier,1 M.P. Hornbak Steenstrup,1 F. Kaminski,1 E. S. Polzik,1 and J. H. Muller1

1Niels Bohr Institute, Blegdamsvej 17, 2100 Copenhagen, Denmark

The process of superradiant Rayleigh scattering is a promising avenue towards the creation of massive multimodeentanglement between atoms and light. The elementary process, creation of correlated pairs of scattered photons andrecoiling atoms, is the resource for entanglement. Recently, established theories of superradiant scattering have beenchallenged by new models predicting a peculiar asymmetry in the detuning parameter of the drive light [1]. Thisasymmetry has been confirmed experimentally, but so far no convincing theoretical model for the asymmetry hasbeen put forward [2].

We present a new experimental study looking at the detuning and power dependence of the superradiant thresholdover an extended parameter region. We discuss the role of spontaneous scattering from isolated atoms and from closepairs inside high density atomic clouds in the initial stages of the superradiant emission in the framework of rateequation and coupled wave models of superradiant scattering [3, 4].

[1] Electromagnetic Wave Dynamics in Matter-Wave Superradiant Scattering, L. Deng, M. G. Payne, E.W. Hagley, Phys. Rev.Lett. (2010).

[2] Observation of a Red-Blue Detuning Asymmetry in Matter-Wave Superradiance, L. Deng, E.W. Hagley, Qiang Cao, XiaoruiWang, Xinyu Luo, Ruquan Wang, M. G. Payne, Fan Yang, Xiaoji Zhou, Xuzong Chen, Mingsheng Zhan, Phys. Rev. Lett.(2011).

[3] Rayleigh superradiance and dynamic Bragg gratings in an end-pumped Bose-Einstein condensate, A. Hilliard, F. Kaminski,R. le Targat, C. Olausson, E.S. Polzik, J. H. Muller, Phys. Rev. A (2008).

[4] Collective enhancement and suppression in Bose-Einstein condensates, W. Ketterle and S. Inouye, arXiv (2001).


59

Study of systematic effects for Newtonian gravitation constant measurement inMAGIA experiment

Y.-H. Lien,1, ∗ G. Rosi,1 F. Sorrentino,1 G. M. Tino,1 L. Cacciapuoti,2 M. de Angelis,3 and M. Prevedelli4

1Dipartimento di Fisica e Astronomia & INFN, Universita di Firenze,via Sansone 1 50019 Sesto Fiorentino (FI), ItalyTel +39 055 457 2031, Fax +39 055 457 2346

2European Space Research and Technology Centre,Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands

3Istituto di Cibernetica CNR, via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy4Dipartimento di Fisica dell’Universita di Bologna, via Irnerio 46, 40126 Bologna, Italy

The development of atom interferometry receives much interest in many applications because of its high sensi-tivity. Accelerometers based on atom interferometry have been proposed or implemented for fundamental physicsexperiments [1] as well as many applications such as metrology [2], geophysics and so on [3].

We will present the study of various systematic effects for accurate measurement of the gravitational constant Gin MAGIA experiment [4]. The experiment is based on a Raman light-pulse atom interferometry gravity gradiometerdetecting the gravitational field generated by a well characterized set of source masses (FIG. 1).

0.70

0.65

0.60

0.55

0.50

0.45

0.40

0.700.650.600.550.500.450.40

14.5 mW 10.5 mW 9.5 mW 5.1 mW

0.7

0.6

0.5

0.4

0.70.60.50.4

FIG. 1: Left: Simplified apparatus diagram. Center: Typical ellipses obtained by plotting the phase of the upper interferometerversus the phase of the lower interferometer, for different source masses positions. The rotation angle of one ellipse respect toanother is a measure of the gravity gradient change due to the source masses. Right: The ellipses with different probe beamparameters.

In order to achieve the proposed goal of 10−4 accuracy on determination of G, we proceeded a series of the scrutinieson several system parameters which the source masses induced ellipse angle might be susceptible to. Besides to theaforementioned studies, we recently explored a systematic shift related to different source masses positions and itcould not be easily suppressed by the current differential measurement scheme. The studies will be presented.

[1] H. Muller et al., A precision Measurement of the Gravitational Redshift by the Interference of Matter Waves, Nature Phys.463 926 (2010).

[2] M. Cadoret et al., Atom Interferometry Based on Light Pulses: Application to the High Precision Measurement of the Ratioh/m and the Determination of Fine Structure Constant, Euro. Phys. J. Spec. Top. 172 121 (2009).

[3] M. de Angelis et al., Precision Gravimetry with Atomic Sensors, Meas. Sci. Technol. 20 022001 (2009).[4] G. Lamporesi et al., Determination of the Newtonian Gravitational Constant Using Atom Interferometry, Phys. Rev. Lett.

100 050801 (2008).

∗Electronic address: [email protected]; URL: http://coldatoms.lens.unifi.it

60

Vortex patterns’ structural changes

N. Lo Gullo,1, ∗ M. Paternostro,1 and Th. Busch1

1Physics Department, University College Cork, Cork, Ireland

We study the changes in the ground state vortex patterns of a 2D rotating Bose-Einstein condensate (BEC) inthe medium rotation regime and under an increasing eccentricity of the trapping potential. We show that the vortexpattern undergoes to a series of structural changes, which include sudden transitions from filled circles to zig-zagand linear shaped configurations. While we explicitly show that such patterns are unstable over long time scales dueto the continuous excitation of the background condensate due to the eccentricity of the trapping potential, we alsoshow that a clear cut signature of the occurrence of these transitions can be found in the behaviour of vortex-patterneigenmodes. In particular the lowest eigenvalues of the vortex pattern vanish at the points where these phase changesoccur.

Even though we concentrate on superfluid vortex systems, our findings apply generally to many-body systems whichsupport vortex-like topological defects, since the only assumption made is the functional form of interaction energy.Our predictions are observable using currently available technologies for creating condensates in time-dependenttrapping potentials (for example via Spacial Light Modulators (SLMs)).


61


C. Basler,1, ∗ F. Meinert,1 A. Lambrecht,1 and H. Helm1

1Department of Molecular and Optical Physics, Physikalisches Institut, Uni-FreiburgStefan-Meier-Str. 19 VF, 79104 Freiburg, Germany

Tel (+49)(0)761 203 7636

A table-top atomic clock based on coherent population trapping (CPT) resonances with parallel linearly polarizedoptical fields in a vapor cell has recently been demonstrated on the D1 line of 87Rb[1]. We study this transition withcounter-propagating laser beams in an optical dipole trap. One goal is to explore the suitability of this transition foran all optical path to continuous generation of low temperature trapped atom samples using the proposed EIT-coolingscheme [2,3]. Due to the low trapping frequencies which can be realized for neutral atoms, a magnetic-field insensitiveCPT resonance transition appears paramount to success. A second attractive feature of this transition is the highcontrast of the resonance amplitude[1]. The experiment is carried out using two externally phase-locked diode lasersand a crossed CO2 laser dipole trap which is loaded from a 2D-MOT.Research supported by DFG HE2525/7

[1] E. E. Mikhailov et al.[2] C. Morigi, Phys. Rev. A. 67 033402 (2003) (2011).[3] M. Roghani et al., Phys. Rev. A 81 033418 (2010)

∗Electronic address: [email protected]; URL: http://frhewww.physik.uni-freiburg.de/

62

Interaction-based reduction of weak localization in coherent transport ofBose-Einstein Condensates

J. Michl,1 T. Hartmann,1 J.-D. Urbina,1 K. Richter,1 C. Petitjean,2 T. Wellens,3 and P. Schlagheck4

1Institut fur theoretische Physik, Universitat Regensburg,Universitatsstraße 31, D-93053 Regensburg, Germany

2SPSMS-INAC-CEA, 17 Rue des Martyrs,F-38054 Grenoble Cedex 9, France

3Institut fur Physik, Albert-Ludwigs-Universitat Freiburg,Hermann-Herder-Str. 3, D-79104 Freiburg, Germany

4Departement de Physique, Universite de Liege,Allee du 6 Aout, 17, B-4000 Liege, Belgium

Based on the Gross-Pitaevskii-equation, we investigate reflection probabilities in the transport of coherent bosonicmatter waves through a fully-chaotic two-dimensional billiard-system. Like in the case of electronic transport, onecan observe the effect of weak localization in this setting. Our interest lies now in the influence of a weak interactionbetween particles on the weak localization peak and its behaviour in the presence of a weak magnetic field in thebilliard.

Numerical results on this topic predict a reduction of the weak localization peak for small magnetic fields and avanishing influence of the interaction with an increasing one. Trying to explain that, an analytical technique based ona semiclassical treatment in form of a diagrammatic perturbation theory in the parameter representing the interactionwill be presented. Its results are compared to the numerical findings.

63

Microscopic dynamics of ultracold particles in a ring-cavity optical lattice

W. Niedenzu,1, ∗ R. Schulze,1, 2 A. Vukics,1 and H. Ritsch1

1Institut fur Theoretische Physik, Universitat InnsbruckTechnikerstraße 25, 6020 Innsbruck, Austria

2Institut fur Ionenphysik und Angewandte Physik, Universitat Innsbruck,Technikerstraße 25, 6020 Innsbruck, Austria

The quantum dynamics of particles optically trapped in a symmetrically pumped high-Q ring cavity exhibits muchricher physics than for a standing-wave resonator. In addition to modifying the lattice depth, light scattering by theparticles shifts and reshapes the trapping potential. We calculate the corresponding changes in tunneling amplitudesand damping by an effective bipotential (two-level) model for the particle motion. As a crude truncation of the Bose-Hubbard model, expansion to the lowest band decouples particle and field dynamics. Only including excitations tohigher bands can capture this essential additional physics and correctly describe decoherence, damping, and long-rangecorrelations of the particle dynamics. The validity limits of the analytic models are confirmed by quantum MonteCarlo wave-function simulations, which exhibit correlated particle-field quantum jumps as unambiguous quantumsignature of the system dynamics.

[1] Microscopic dynamics of ultracold particles in a ring-cavity optical lattice, W. Niedenzu, R. Schulze, A. Vukics, and H.Ritsch, Phys. Rev. A 82, 043605 (2010).


64

Localized and Extended states in a disordered trap

L. Pezze1, ∗ and Laurent Sanche-Palencia1

1Laboratoire Charles Fabry de l’Institut d’Optique, CNRS and Univ. Paris-Sud,Campus Polytechnique, RD 128, F-91127 Palaiseau cedex, France

We study Anderson localization in a disordered potential combined with an inhomogeneous trap. We show thatthe spectrum displays both localized and extended states, which coexist at intermediate energies. In the regionof coexistence, we find that the extended states result from confinement by the trap and are weakly affected by thedisorder. Conversely, the localized states correspond to eigenstates of the disordered potential, which are only affectedby the trap via an inhomogeneous energy shift. These results are relevant to disordered quantum gases and we proposea realistic scheme to observe the coexistence of localized and extended states in these systems.

[1] Localized and Extended States in a Disordered Trap, L. Pezze and L. Sanchez-Palencia, Phys. Rev. Lett. 106, 040601 (2011).


65

Three-body correlation function and recombination rate in one-dimensional systems

M. Rabie,1 E. Haller, M.J. Mark, J.G. Danzl, K. Lauber, A. Klinger, O.Krieglsteiner,1 A.Klinger,1 O. Krieglsteiner,1 G. Pupillo,2 and Hans-Christoph Nagerl1

1Institut fur Experimentalphysik und Zentrum fur Quantenphysik, Universitat InnsbruckTechnikerstrasse 25/4, 6020 Innsbruck, Austria

2Institut fur Quantenoptik und Quanteninformation (IQOQI),

Osterreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria

We investigate the dependence of the local three-body correlation function of a one-dimensional Bose gas on theLieb-Liniger parameter γ , including 1D mean-field regime, Tonks-Girardeau gas as well as the intermediate regime.We load a Bose-Einstein condensate into a two dimensional optical lattice and tune interactions by means of magenticFeshbach resonances. The local three-body correlation function is determined from the three-body recombinationrate in 1D and 3D geometry. For the highly correlated Tonks gas we find a strong suppression of recombinations,corresponding to a reduction of the three-particle correlation function by three orders of magnitude. We get goodagreement with theoretical predictions in all regimes.

66

Design of a high-power frequency-doubled laser system for an optical superlattice forultracold cesium atoms

Lukas Reichsollner,1, ∗ Johann G. Danzl,1 Manfred J. Mark,1 Andreas Klinger,1

Oliver Kriegelsteiner,1 Mohamed Rabie,1 and Hanns-Christoph Ngerl1

1Institut fur Experimentalphysik und Zentrum fur Quantenphysik, Universitat InnsbruckTechnikerstrasse 25/4, 6020 Innsbruck, AustriaTel +43 512 507-6331, Fax +43 512 507-2921

Ultracold quantum gases are ideal systems for studies on matter-wave physics, for the investigation of quantumphase transitions and new quantum phases, for quantum chemistry at zero temperature, and for the realization ofnovel quantum information schemes.

We present a laser design for implementing a so-called optical superlattice for experiments with ultracold cesiumatoms and molecules. This superlattice consists of two superimposed optical lattices which can be controlled inde-pendently of each other. The first lattice operates at 1064 nm whereas the second lattice has a wavelength of 532nm.

The green light is obtained by first amplifiying the 1064 nm light with a home-built fiber amplifier and thenfrequency doubling in a high-power bowtie cavity setup. With this scheme, phase stabilty of the two lattices withrespect to each other can be ensured. In the experiment, we will use the superlattice to optimize molecule productionefficiency from quantum degenerate atomic samples and to investigate novel quantum phase transitions.

∗Electronic address: [email protected]; URL: http://ultracold.at

67

Atom chip based generation of entanglement for quantum metrology

M. F. Riedel,1, ∗ P. Bohi,1 C. Ockeloen,1 R. Schmied,1 and P. Treutlein1

1Departement Physik, Universitat BaselKlingelbergstrasse 82, 4056 Basel, Switzerland

Tel +41 61 267-3714

The essence of all quantum technologies, such as quantum information processing, quantum simulations, and quan-tum metrology, lies in the generation and use of entanglement. These technologies have the potential to revolutionizeour way of computing and measuring; and through their development we hope to tackle the puzzling concept ofentanglement itself. Ultracold atoms on atom chips are attractive for the implementation and advancement of quan-tum technologies, as they provide control over quantum systems in compact, robust, and scalable setups. A severelimitation of atom chips, however, is that techniques to control atomic interactions and thus to generate entanglementhave not been experimentally available so far.

Here, we present experiments where we generate multi-particle entanglement on an atom chip [1] by controllingelastic collisional interactions with a state-dependent microwave near-field potential [2]. We employ this techniqueto generate spin-squeezed states of a two-component Bose-Einstein condensate and show that they are useful forquantum metrology. The observed reduction in spin noise combined with the spin coherence imply four-partiteentanglement between the condensate atoms and could be used to improve an interferometric measurement over thestandard quantum limit. Our data show good agreement with a dynamical multi-mode simulation [3] and allow usto reconstruct the Wigner function of the spin-squeezed condensate [4]. The techniques demonstrated here could bedirectly applied in chip-based atomic clocks which are currently being set up. Furthermore, they constitute the keyingredient for a quantum phase gate which was previously proposed [5].

[1] Atom chip based generation of entanglement for quantum metrology, M. F. Riedel et al., Nature 464, 1170 (2010).[2] Coherent manipulation of Bose-Einstein condensates with state-dependent microwave potentials on an atom chip, P. Bohi

et al., Nat. Phys. 5, 592 (2009).[3] Spin squeezing in a bimodal condensate: spatial dynamics and particle losses, Y. Li, P. Treutlein, J. Reichel, A. Sinatra,

Eur. Phys. J. B 68, 365 (2009).[4] Tomographic reconstruction of the Wigner function on the Bloch sphere, R. Schmied, P. Treutlein, arXiv:1101.4131 (2011).[5] Microwave potentials and optimal control for robust quantum gates on an atom chip, P. Treutlein et al., Phys. Rev. A 74,

022312 (2006).

∗Electronic address: [email protected]; URL: http://atom.physik.unibas.ch

68

A ring trap for matter-wave interferometry

B. E. Sherlock,1, ∗ M. Gildemeister,1 E. Owen,1 E. Nugent,1 and C. J. Foot1

1Clarendon LaboratoryParks Road, Oxford, OX1 3PU, United Kingdom

Tel +44 1865 282201

We present experimental data on a novel ring trap with smoothly adjustable radius and a lifetime well suited tocold atom experiments. The toroidal geometry is generated by the application of an oscillating magnetic bias fieldto a radio-frequency (rf) dressed quadrupole trap. The result is a Time-Averaged Adiabatic Potential (TAAP)[1][2]with an annular minimum, the radius of which can be dynamically varied from 50µm to 250µm. Control over the ringradius allows the trap two be operated in two distinct regimes. For large ring radii the trap forms a smooth circularwaveguide with notable advantages for matterwave interferometry such as a large enclosed area and the absence ofa net magnetic moment due to the atoms being trapped in a balanced superposition of Zeeman substates. For ringradii < 60µm the quantum coherence fills the ring presenting an opportunity to study the superfluid properties of adilute ultracold quantum gas.

The ring trap is conveniently loaded from a conventional time-averaged orbiting potential trap, with minimalheating and atom loss. We have measured oscillation frequencies of atoms in the potential which present goodagreement with our theoretical model. Refinements to the ring geometry can be achieved via controlled adjustmentsto the polarisation of the rf dressing field. Correction for gravitational asymmetries and a rotation scheme have beenimplemented following this method. A Bose-Einstein condensate has been loaded into the large ring configurationand its motion around the ring has been observed.

[1] Time-Averaged Adiabatic Potentials: Versatile Matter-Wave Guides and Atom Traps, Igor Lesanovsky and Wolf von Klitz-ing, Phys. Rev. Lett. 99, 083001 (2007).

[2] Trapping ultracold atoms in a time-averaged adiabatic potential, M. Gildemeister, E. Nugent, B. E. Sherlock, M. Kubasik,B. T. Sheard and C. J. Foot, Phys. Rev. A 81, 031402(R) (2010).

∗Electronic address: [email protected]; URL: http://www-matterwave.physics.ox.ac.uk/

69

Strontium in an Optical Lattice as a Mobile Frequency Reference

Yeshpal Singh,1 Ole Kock,1 Steven Johnson,1 and Kai Bongs1

1School of Physics and AstronomyUniversity of Birmingham

Edgbaston Park Road, Birmingham B15 2TT, UK

The higher frequencies (1015 Hz) of the atomic transitions enable a greater accuracy than the current microwavefrequency (1010 Hz) standard. Optical clocks have now achieved a performance significantly beyond that of the bestmicrowave clocks, at a fractional frequency uncertainty of 8.6 · 10−18 [1]. With the rapidly improving performanceof optical clocks, in the future, most applications requiring the highest accuracy will require optical clocks. We aresetting up an experiment aimed at a mobile frequency standard based on strontium (Sr) in a blue detuned opticallattice. Sr is an alkaline-earth element and has two electrons in its outer shell, which give rise to a singlet state (groundstate) and a triplet state. The dipole transitions from a singlet state to a triplet state are forbidden, which resultsin a long meta-stable lifetimes and as narrow line widths as one mHz. The unprecedented accuracy in time promisesnew applications like relativistic geodesy for exploration of oil and minerals, fundamental tests of general relativityand synchronization for long base line astronomical interferometry. It is worth mentioning that very recently, spacehas also opened up as a new venue for precision measurements based on cold atoms. An up to date progress on acompact and robust frequency standard experiment will be presented.

[1] C.W. Chou, D. B. Hume, J. C. J. Koelemeij, D. J. Wineland, and T. Rosenband, PRL 104, 070802 (2010)

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Continuous approach to cold atom interferometers

A. Joyet, L. Devenoges, G. Di Domenico, and P. ThomannLaboratoire Temps - Frequence (LTF)

University of Neuchatel

Av. de Bellevaux 51, 2009 Neuchatel, Switzerland


Abstract

Matter-wave interferometers using cold neutralatoms can be used to realize precision measure-ments of various physical quantities. Nowadaysthese instruments are based on a sequential modeof operation. Atoms are first prepared in a definedquantum state, then optically interrogated and fi-nally detected before a new such sequence startsagain. This kind of operation may suffer from adegradation of the measurement stability due todead times (Dick effect) which is well known inpulsed microwave fountain clocks for example.

In the case of a fountain clock, we have shownthat a continuous mode of operation allows to keepthe stability degradation to a negligible level com-pared to the shot-noise limited stability [1]. Fromthat point of view, a continuous approach to coldatom interferometers could be advantageous to im-prove their ultimate sensitivity as our theoreticalanalysis of the aliasing noise in a cold atom gyro-scope shows it [2]. Moreover, for such an approach,the necessary technology components developed forour continuous fountain clocks could also be usefullto cold atom interferometers.

The first component is the source of the contin-uous cold and slow atomic beam. It consists of a3D-optical molasses, loaded by an efficient contin-uous 2D-MOT pre-source [3], that provides a slow(adjustable velocity of a few m/s), cold (70µK) andhigh atomic flux(1 · 1010 at/s) continuous beam.

The second component, located at the output ofthe molasses, realizes an efficient transverse colli-mation of the beam. It is achieved through a 2D-optical lattice perpendicular to the atomic beamthat uses Sisyphus cooling to reduce the transversetemperature down to 4µK.

The quantum state preparation of the atoms isthe next component that follows the collimationstage. It combines state selection with Sisyphuscooling to avoid reheating of the atoms. Trans-verse cooling is achieved by another 2D-optical lat-tice superposed with Zeeman pumping that putsthe atoms in the F = 3,m = 0 state [4].

The last and key component is specific to a con-tinuous approach. With the use of a continuousbeam, light emitted from the source can reach theregion where the atoms are interrogated and per-turbs the measurement. To avoid that we have de-veloped a rotating light-trap, located after the statepreparation stage, that removes the light from theatomic beam. It is composed of an electrostaticmotor that drives a turbine whose blades are madeof absorbing glass [5].

This contribution gives an overview and currentstatus of the technology used in a continuous ap-proach as well as a first quantitative analysis of thepotential improvement in sensitivity that can beexpected for a cold atom gyroscope.

References

[1] J. Guena, G. Dudle, and P. Thomann, Eur.Phys. J. Appl. Phys. 388, 183-189 (2007).

[2] A. Joyet, et al., To be published.

[3] N. Castagna, et al., Eur. Phys. J. Appl. Phys.34, 21-30 (2006).

[4] G. Di Domenico, et al., PRA 82, 053417(2010).

[5] F. Fuzesi, et al., Rev. Sci. Instrum. 78, 103109(2007).

71

Strongly Correlated Ultracold Fermions in Disordered Optical Lattices

J. Wernsdorfer,1, ∗ U. Bissbort,1 Y. Li,1 S. Gotze,1 J. Heinze,1 J. S.Krauser,1 M. Weinberg,1 C. Becker,1 K. Sengstock,1 and W. Hofstetter1

1Institut fur Theoretische Physik, Johann Wolfgang Goethe-Universitat, 60438 Frankfurt/Main, Germany

The Anderson-Hubbard model incorporating disorder and correlations will be analyzed by means of real-spacedynamical mean field theory (R-DMFT) and statistical dynamical mean field theory (stat DMFT).

By comparing the ground state phase diagram in the presence of box disorder obtained by DMRG with thatobtained by R-DMFT in 1D, the accuracy of the latter method is discussed in this regime. Mott insulating, Andersonlocalized and quasi-metallic regimes are characterized on the basis of the local density of states and the appearanceof an energy gap in the excitation spectrum.

Furthermore, the interplay of disorder and interactions is studied in two- and three- spatial dimensions for the caseof experimentally realistic speckle disorder. We obtain a complete paramagnetic ground state phase diagram and finda strong suppression of the correlation-induced metal insulator transition due to disorder. In remarkable contrast tothe case of box disorder, our results indicate that the Anderson-Mott and the Mott insulator are not continuouslyconnected due to the specific character of speckle disorder.


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Frontiers of Matter Wave Optics · Laboratoire Charles Fabry de l'Institut d'Optique, Campus...

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Transcript of Frontiers of Matter Wave Optics · Laboratoire Charles Fabry de l'Institut d'Optique, Campus...