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Ideas for Experimental Realization of Neutral Atom Quantum Computing

Ideas for Experimental Realization of Neutral Atom Quantum Computing. 演 講 者：蔡 錦 俊 成功大學物理系 chintsai@mail.ncku.edu.tw http://www.phys.ncku.edu.tw/~cctsai 2002 年 10 月 18 日. Outline. Motivation. Entanglement of two Macroscopic Objects. Trapping and manipulation of Single or Few Atoms.

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Ideas for Experimental Realization of Neutral Atom Quantum Computing

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  1. Ideas for Experimental Realization of Neutral Atom Quantum Computing 演 講 者：蔡 錦 俊 成功大學物理系 chintsai@mail.ncku.edu.twhttp://www.phys.ncku.edu.tw/~cctsai 2002年10月18日

  2. Outline • Motivation • Entanglement of two Macroscopic Objects • Trapping and manipulation of Single or Few Atoms

  3. Motivation Using neutral atoms to realize quantum computing Advantages: Atoms, photons, and fields are involved Weak interactions with external fields Many internal states Long-lived coherence time Disadvantages: Exponential decrease of preparing efficiency Noise and imperfections in setup

  4. Entanglement of two Macroscopic Objects / Nature 413, 400 (2001), Aarhur, Denmark. Experimental set-up and the sequence of optical pulses.

  5. Entanglement of two Macroscopic Objects / Nature 413, 400 (2001), Aarhur, Denmark. 2S+1, S=1/2 n=6 6p 2P3/2 F=3, mF Cs 6s 2S1/2 -4, -3, -2, -1, 0, 1, 2, 3, 4 l=0 J=1/2 s+ -4, -3, -2, -1, 0, 1, 2, 3,4 6s 2S1/2 F=4, mF Nuclear spin, I=7/2 F = J+I Internal state of neutral Cs atoms and optical pumping

  6. Entanglement of two Macroscopic Objects / Nature 413, 400 (2001), Aarhur, Denmark. Sample: Two 3x3 cm paraffin coated cells place in a highly homogenous B field 0f 0.9 G. Coherence time of spin-state 5~30 msec Optical pumping: Cell1: |F=4, mF=4>; Cell2: |F=4, mF=-4> Optical pulses: 0.45msec, 0.5 mW at 852 nm with 700 MHz of blue detuned. Entangling pulse and verifying pulse are separated by 0.5 msec, no entanglement at 0.8 msec.

  7. Entanglement of two Macroscopic Objects / Nature 413, 400 (2001), Aarhur, Denmark. Cos(Wt) and Sin(Wt) Special variance: D= (Sycos(W))2 + (Sysin(W))2 out out Measurement

  8. Entanglement of two Macroscopic Objects / Nature 413, 400 (2001), Aarhur, Denmark. Normalized special variance DEPR/D(Jx) vs. Jx Below unity level for entangled State of the two atomic samples Maximum possible entanglement (dotted line) Shot noise of verifying pulse (dashed line) Degree of entanglement x = (35+7)%

  9. Trapping and manipulation of Single or Few Atoms Single atom trap/ Science 293, 278 (2001), Bonn, Germany • Advantages for dipole trapping: • Trap all spin states • Very long spin relaxation time ~ 30 sec • High Modulation speed Normal MOT device Dipole Trap : Nd:YAG laser, l=1064nm, counter propagated, Beam waist w0 ~ 30mm Dipole potential, U(z, t) = U0cos[p(Dnt-2z/l)] Dn controlled with two acousto-optic modulation (AOM) Detection: position sensitive LIF at Cs F=4 F’=5 and Repumping at F=3F’=4

  10. Trapping and manipulation of Single or Few Atoms Single atom trap/ Science 293, 278 (2001), Bonn, Germany Experimental set-up

  11. Trapping and manipulation of Single or Few Atoms Single atom trap/ Science 293, 278 (2001), Bonn, Germany Few atoms detection

  12. Quantum Tweezer for Atoms Deterministic loading of single atom/PRL 89,70401(2002),Austin,USA The probability of extracting a single atom vs. dot speed. Using 1D BEC harmonic trap, N=105 and square dot well. Loading atom from a Condensate and dot potential Good for extracting definite number of neutral atoms from reservoir, Bose-Einstein condensation.

  13. The End

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