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Aiming at Quantum Information Processing on an Atom Chip

Aiming at Quantum Information Processing on an Atom Chip. Caspar Ockeloen. Outline. Quantum Information with Ultracold Atoms Magnetic lattice atom chip Atom number fluctuations Conclusion. Quantum Information. Requirements: Scalable Long coherence time Nearest neighbor interactions.

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Aiming at Quantum Information Processing on an Atom Chip

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  1. Aiming at Quantum Information Processing on an Atom Chip Caspar Ockeloen

  2. Outline • Quantum Information with Ultracold Atoms • Magnetic lattice atom chip • Atom number fluctuations • Conclusion

  3. Quantum Information Requirements: • Scalable • Long coherence time • Nearest neighbor interactions

  4. Kelvin 104 – 103 – 102 – 101 – 1 – 10-1 – 10-2 – 10-3 – 10-4 – 10-5 – 10-6 – 10-7 – – Solar surface – Room temperature – High TC superconductor – Liquid Helium – Ultracold atoms Ultracold Atoms • Clean and isolated Quantum systems • Coherence time up to 1 minute!

  5. Magnetic lattice atom chip Magnetic FePt film + External B-field Magnetic trapping 22 µm Rubidium atoms (mK) 10-1000 atoms per trap Lattice of ~500 traps Goal: each trap ↔ 1 qubit

  6. B B p=ħk Magnetic lattice atom chip Trapping and manipulating atoms • Ultra high vacuum + atom chip • Lasers + magnetic field trap atoms • Cooled to several mK • Transfer atoms to microtraps • Image atoms with CCD camera CCD

  7. Absorption Imaging Atom chip Absorption image of full lattice CCD S. Whtilock et al “Two-dimensional array of microtraps with atomic shift register on a chip”, NJP, (2009)

  8. Single site manipulation How to make qubits? Optically address single sites Transport all atoms across the lattice

  9. Collective excitations • One excitation shared over ensemble • Highly entangled state • Potentially more robust and faster • Excitation rate depends on atom number Requires small and well defined ensembles of atoms

  10. Classical limit: Shot Noise • Atoms are discrete particles • Poisson distribution: N ± √N atoms

  11. Three-body loss • Dominant loss process • Three atoms → Molecule + Free atom • 3-body interaction: density dependent

  12. Initial distribution 3-body loss Poisson distribution Three-body loss Effects on atom number distribution Poisson distribution N = 100 sN = 10

  13. Three-body loss Mean atom number Fluctuations F=0.6 Fano factor: F = 1 ↔ Poisson

  14. Mean atom number (a)

  15. Fluctuations Sub-Poissonian! S. Whitlock, C. Ockeloen, R.J.C Spreeuw, PRL 104, 120402 (2010)

  16. Fluctuations F = 0.5 ± 0.2 for 50 < N < 300 Not limited by technical noise Fluctuations below classical limit Promise for high fidelity operations Ideal starting point for Quantum Information

  17. Conclusions Magnetic lattice atom chip > 500 atom clouds Optically resolved and addressable Sub-Poissonian atom number fluctuations F = 0.5 ± 0.2 Promising platform for Quantum Information

  18. Outlook • Long range interactions • New lattice design • New geometries • 5 mm spacing • In vacuum imaging • Quantum Computer...

  19. Thank 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)

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