Transcript Slide 1
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 Ultracold Atoms Kelvin – 103 – 102 – 101 – 1– 10-1 – 10-2 – 10-3 – 10-4 – 10-5 – 10-6 – 10-7 – 104 – Solar surface – Room temperature – High TC superconductor – Liquid Helium – Ultracold atoms • Clean and isolated Quantum systems • Coherence time up to 1 minute! Magnetic lattice atom chip Magnetic trapping Magnetic FePt film + External B-field Rubidium atoms (mK) 10-1000 atoms per trap Lattice of ~500 traps Goal: each trap ↔ 1 qubit Magnetic lattice atom chip Trapping and manipulating atoms • Ultra high vacuum + atom chip • Lasers + magnetic field trap atoms • Cooled to several mK B B • Transfer atoms to microtraps p=ħk • Image atoms with CCD camera CCD Absorption Imaging Absorption image of full lattice CCD Atom chip S. Whtilock et al “Two-dimensional array of microtraps with atomic shift register on a chip”, NJP, (2009) Single site manipulation • Optically address single sites • Transport all atoms across the lattice How to make qubits? 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 Classical limit: Shot Noise • Atoms are discrete particles • Poisson distribution: N ± √N atoms Three-body loss • Dominant loss process • Three atoms → Molecule + Free atom • 3-body interaction: density dependent Three-body loss Effects on atom number distribution Initial distribution 3-body loss Poisson distribution Poisson distribution N = 100 sN = 10 Three-body loss Mean atom number Fluctuations F =0.6 Fano factor: F = 1 ↔ Poisson Mean atom number (a) Fluctuations Sub-Poissonian! S. Whitlock, C. Ockeloen, R.J.C Spreeuw, PRL 104, 120402 (2010) 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 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 Outlook • Long range interactions • New lattice design – New geometries – 5 mm spacing – In vacuum imaging • Quantum Computer... Thank you S. Whitlock, C. Ockeloen, R.J.C Spreeuw, “Sub-Poissonian AtomNumber 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, “Twodimensional array of microtraps with atomic shift register on a chip,” New J. Phys. 11, 023021 (2009)