Aiming at Quantum Information Processing on an Atom Chip
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Transcript of Aiming at Quantum Information Processing on an Atom Chip
Aiming at Quantum Information Processing on an Atom Chip
Aiming at Quantum Information Processing on an Atom Chip
Caspar Ockeloen
OutlineOutline
• Quantum Information with Ultracold Atoms
• Magnetic lattice atom chip
• Atom number fluctuations
• Conclusion
Quantum InformationQuantum Information
Requirements:
• Scalable
• Long coherence time
• Nearest neighbor interactions
Ultracold AtomsUltracold Atoms
• Clean and isolated Quantum systems
• Coherence time up to 1 minute!
104 –103 –102 –101 –
1 –10-1 –10-2 –10-3 –10-4 –10-5 –10-6 –10-7 –
– Liquid Helium
– Ultracold atoms
– Solar surface
– Room temperature
Kelvin
– High TC superconductor
Magnetic lattice atom chipMagnetic lattice atom chip
22 µm
Magnetic FePt film+
External B-field
Rubidium atoms (K)10-1000 atoms per trap
Lattice of ~500 traps
Goal: each trap ↔ 1 qubit
Magnetic trapping
Magnetic lattice atom chipMagnetic lattice atom chip
BB
Trapping and manipulating atoms
• Ultra high vacuum + atom chip
• Lasers + magnetic field trap atoms
• Cooled to several K
• Transfer atoms to microtraps
• Image atoms with CCD camera
CCD
p=ħk
Absorption ImagingAbsorption Imaging
S. Whtilock et al “Two-dimensional array of microtraps with atomic shift register on a chip”, NJP, (2009)
Atom chip
Absorption image of full lattice
Single site manipulationSingle site manipulation
• Optically address single sites
• Transport all atoms across the lattice
How to make qubits?
Collective excitationsCollective excitations
Requires small and well defined ensembles of atoms
• One excitation shared over ensemble
• Highly entangled state
• Potentially more robust and faster
• Excitation rate depends on atom number
Classical limit: Shot NoiseClassical limit: Shot Noise
• Atoms are discrete particles
• Poisson distribution: N ± √N atoms
Three-body lossThree-body loss
• Dominant loss process
• Three atoms → Molecule + Free atom
• 3-body interaction: density dependent
Three-body lossThree-body loss
Effects on atom number distribution
Initial distribution3-body lossPoisson distribution
Poisson distributionN = 100 N = 10
F =0.6
Fluctuations
Fano factor:F = 1 ↔ Poisson
Three-body lossThree-body loss
Mean atom number
Mean atom numberMean atom number
(a)
FluctuationsFluctuations
Sub-Poissonian!
S. Whitlock, C. Ockeloen, R.J.C Spreeuw, PRL 104, 120402 (2010)
FluctuationsFluctuations
Not limited by technical noise
Fluctuations below classical limit
Promise for high fidelity operations
Ideal starting point for Quantum Information
F = 0.5 ± 0.2 for 50 < N < 300
ConclusionsConclusions
Magnetic lattice atom chip
> 500 atom clouds
Optically resolved and addressable
Sub-Poissonian atom number fluctuations
Promising platform for Quantum Information
F = 0.5 ± 0.2
OutlookOutlook
• Long range interactions
• New lattice design – New geometries– 5 m spacing– In vacuum imaging
• Quantum Computer...
Thank youThank you
S. Whitlock, C. Ockeloen, R.J.C Spreeuw, “Sub-Poissonian Atom-Number Fluctuations by Three-Body Loss in Mesoscopic Ensembles,” Phys. Rev. Lett. 104, 120402 (2010)
S Whitlock, R Gerritsma, T Fernholz and R J C Spreeuw, “Two-dimensional array of microtraps with atomic shift register on a chip,” New J. Phys. 11, 023021 (2009)