~ 12 mm Neutral atom quantum computing in optical lattices: far red or far blue
Adair, Jill, News Services Editor has reference to this Academic Journal, PHwiki organized this Journal ~ 12 mm Neutral atom quantum computing in optical lattices: far red or far blue C. S. Adams University of Durham 17 November 2004 University of Durham Outline University of Durham Good things as long as quantum computing Scalability (optical lattices) Low decoherence (large detuning) Far-red Far-blue 3D CO2 single-site addressable Switchable interactions State-selective single-atom transport Collisional gates Experiment Magic Rydberg lattice or (i) Neutral atoms in optical lattices. Single-qubit addressable. – Patterned loading – Pointer Switchable interactions. – Cavity QED – Collisions – Rydberg Scaling to 2(3)D. Low decoherence. University of Durham Ions. Single-qubit addressable. Switchable interactions. Scaling to 2(3)D. Low decoherence. Architecture as long as a large-scale ion-trap quantum computer, D. Kielpinski, C. Monroe, D.J. Winel in addition to Nature, 417, 709 (2002). Quantum computing: atoms or ions 2. Neutral atoms: (i) Optical lattices (optical microtraps); (ii) Atom chips. O. M in addition to el, M. Greiner, A. Widera, T. Rom, T. W. Hänsch, in addition to I. Bloch Controlled collisions as long as multi-particle entanglement of optically trapped Atoms, Nature, 425, 937 (2003)
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University of Durham Photon scattering rate as long as a trap frequency of 1 MHz 1000 s-1 at 790 nm! Nd:YAG CO2 0.002s-1 Rb 5p 6p 7p 5p 6p 5s 7p Far red Far blue Far red Far blue: less power Low decoherence nx ~ 100 kHz C. S. Adams et al. J. Phys. B. 36, 1933 (2003). University of Durham Far infrared: 3D CO2 lattice ~ 12 mm q = atan(2) q 1. 11.8 mm lattice constant: single-atom addressable. Similar trap depths as long as most atoms (molecules). P = 80 W w0=50 mm Saddle ny ~ 75 kHz Single-atom conveyor 8.4 mm Photon scattering rate Blue Red Single-atom tweezer Diener et al. Phys. Rev. Lett. 36, 1933 (2003). University of Durham Wavelength Range Near-infra-red Spin-dependent lattice
Single-atom cooling in addition to detection Fluorescence detection Problem: Optical pumping in addition to heating Solid angle 1/100 Detect 100 photons (1 ms) Heating 2 mK Raman sideb in addition to cooling Repumper C. Monroe, D.M. Meekhof, B.E. King, S.R. Jefferts, W.M. Itano, D.J. Winel in addition to , in addition to P. Gould, Resolved-sideb in addition to Raman cooling of a bound atom to the 3D zero-point energy, Phys. Rev. Lett. 75, 4011 (1995). 87Rb University of Durham Single-atom addressability Stimulated Raman transitions. Single-atom cooling in addition to detection. Single-site addressable. Single-qubit rotations. State-selective single atom transport. ~ 12 mm ~ 5 mm 87Rb University of Durham 2P3/2 2P1/2 2S1/2 I = 3/2 2P3/2 2P1/2 2S1/2 I = 3/2 2P3/2 2P1/2 2S1/2 I = 3/2 State-selective transport Left circular 421.1 nm selects Right circular 421.4 nm selects University of Durham 6p 2P 5s 2S1/2 Spin-dependent lattice O. M in addition to el et al., Nature, 425, 937 (2003). Separate trapping in addition to transport: 104 times less photon scattering during gate operation!
Collisional gates Collisional phase shift move p/2 p/2 p/2 p/2 p/2 p/2 p/2 p/2 move University of Durham Magnetically insensitive storage mF = -2 mF = +1 mF = +2 mF = -1 F = 2 F = 1 Raman selection pulse + 790.0 nm move beam p/2 p/2 p p p p p/2 p/2 2P3/2 2P1/2 2S1/2 I = 3/2 University of Durham detection detection 2. Computation 1. Initialisation 3. Read-out Scalable neutral atom quantum computer University of Durham Detection is not state specific but transport is!
University of Durham Lifetime 6.5 s pressure limited CO2 trap experiment Solder seal windows Hard solder: melting point 309 oC Tested to 275 oC. Reusable. Flexibility: high optical quality, any substrate, any coating. 5. ZnSe saving – £750 per window! 1st baking cycle at 2.3 Nm 2nd baking cycle at 2.5 Nm Ultimate pressure of pumping station S. G. Cox et al. Rev. Sci. Instrum. 74, 1311 (2003); K. J. Weatherill et. al. in preparation University of Durham Pyramid MOT 10-9 Torr Science MOT 10-11 Torr Cold atom beam Large diameter laser beam 3D chamber University of Durham
An optical lattice with single lattice site optical control as long as quantum engineering R Scheunemann, F S Cataliotti, T W Hänsch in addition to M Weitz, J. Opt. B 2, 645 (2000). Loading deep CO2 lattices CO2 CO2+Nd:YAG University of Durham CO2 Nd:YAG 1D lattice BEC at one site: – reservoir as long as extracting single atoms 1. State-selective (site-specific) transport: blue detuning: low scattering high trap frequency faster gates magnetically insensitive storage. Collisional interactions: slow (not switchable) motional decoherence. Disadvantages: CO2 laser University of Durham Advantages: single-site addressable 3D CO2 trap collisional gates G.M. Lankhuijzen in addition to L.D. Noordam, PRL 74, 355 (1995). D. Jaksch, J.I. Cirac, P. Zoller, S.L. Rolston, R. Cote, M.D. Lukin, Fast quantum gates as long as neutral atoms, Phys. Rev. Lett. 85, 2208 (2000). 780 nm 483 nm Ionisation rate R. M. Potvliege University of Durham Rydberg gates ~ 10 mm
Low decoherence University of Durham Photon scattering rate as long as a trap frequency of 1 MHz Blue Red – U0 0 Far red Far blue 1000 s-1 at 790 nm! Nd:YAG CO2 0.002s-1 Rb 5p 6p 7p 5p 6p 5s 7p 0 U0 428 nm 13d More blue! University of Durham Davidson, Lee, Adams, Kasevich, in addition to S. Chu, PRL. 74, 1311 (1995). 4 s Ramsey fringes! Rb model potential calculation R.M. Potvliege in addition to C.S. Adams, preprint 13d 10d 5s 10d 428 nm Magic Rydberg lattice 488 nm 514 nm Long coherence But 428 nm loose single-site addressable! 2P3/2 2P1/2 2S1/2 I = 3/2 428 nm 428 nm 421 nm 6p 2P University of Durham One quantum computer with a pointer Global addressing of a cluster state 2p pulse on a free bound transition O. M in addition to el, M. Greiner, A. Widera, T. Rom, T. W. Hänsch, in addition to I. Bloch Controlled collisions as long as multi-particle entanglement of optically trapped Atoms, Nature, 425, 937 (2003) A. Kay, CSA in addition to J. Pachos, preprint
University of Durham 428 nm lattice proposal R.M. Potvliege in addition to C.S. Adams, preprint Rb-87 BEC Mott Insulator 2. Local addressing with a pointer 3. Patterned loading 4. Rydberg gates + state selective transport to per as long as m read-out 125 mW in 50 mm 100 kHz @ 428 nm S. Peil et al. PRA 67, 051603 (2003). Accordion lattice 780 nm loads every 5th site of 428 nm lattice £75k! Optical lattices: scalability Low decoherence Far-red Far-blue 3D CO2 single-site addressable Switchable interactions State-selective single-atom conveyor Collisional gates Experiment Magic Rydberg lattice Conclusions University of Durham Scalable up to 103 qubits Spatially discriminated parallel read-out Acknowledgements Collaborators: Robert Potvliege (Rydberg theory) Graduate students: Paul Griffin Kevin Weatherill Matt Pritchard Research assistants: Simon Cox (up to 08/04) Collaborators: Erling Riis (Strathclyde) Ifan Hughes, Simon Cornish Technical support: Robert Wylie (Strathclyde) Financial support: EPSRC http://massey.dur.ac.uk/ University of Durham
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