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Ideas for Experimental Realization of Neutral Atom Quantum Computing

This lecture by Dr. Chintai Tsai from National Cheng Kung University discusses the experimental realization of quantum computing using neutral atoms. Emphasizing the benefits and challenges, the talk covers entanglement of macroscopic objects, trapping and manipulating single atoms, and the mechanisms of quantum state preparation. Highlights include advantages of long-lived coherence time and weak interactions with fields, alongside drawbacks like preparation efficiency and setup noise. Key publications and experimental setups are presented to illustrate advancements in the field.

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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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