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Single Atoms in Rotating Ring Optical Lattices

KITPC: Condensed Matter Physics of Cold Atoms ---- Optical Lattices II. Single Atoms in Rotating Ring Optical Lattices. Mingsheng ZHAN ( 詹明生 ) State Key Lab of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, CAS

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Single Atoms in Rotating Ring Optical Lattices

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  1. KITPC: Condensed Matter Physics of Cold Atoms ---- Optical Lattices II Single Atoms in Rotating Ring Optical Lattices Mingsheng ZHAN (詹明生) State Key Labof Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, CAS Center for Cold Atom Physics, CAS Oct 15, 2009 Beijing

  2. Motivation • quantum simulation • quantum computing • single photon source • single atom physics

  3. quantum simulation mimic an unknown system using a controllable system

  4. Hubbard model Approximate model that describes electrons in solids Hamiltonian describes fermions /bosons in a periodic potential Simple, yet hard to solve analytically, numerically or empirically X J U i=1 i=2 i=3 i=4 i=5 John C. Hubbard at 1963 J tunneling U in site interactionexternal potential

  5. Quantum logic gates • Need of experimental aspects: • single atoms • cooled to ground state • double-well • readout U.Dorner, T.Calarco, P.Zoller, A. Browaeys and P. Grangier, J. Opt. B: Quantum Semiclass. Opt. 7 (2005) S341–S346

  6. Atom array by dipole trap (bottom-up) Ultracold atoms in lattices (top-down) single atom dipole trap array cooling the array ultracold gas optical lattices addressing individual atoms The same goal by different routes (殊途同归) （for quantum simulation）

  7. Optical Dipole Trap for Atoms Atom Laser Cylindrically symmetric harmonic oscillator

  8. Superfluidity limit + + + + Good phasei， but Poissonic number

  9. Mott Insulator State Fockstate + + + + good number, But no phase M. Greiner, O. Mandel, T. Esslinger, T. Hansch, I. Bloch, Nature 415 (2002) 39.

  10. P.Grangier’s group[IO/CNRS]

  11. "Collision blockade” RE: Radiative Escape process FCC: Fine-structure Changing Collision Phys. Rev. Lett. 89, 023005 (2002) Nature 411, 1024 (2001).

  12. D.Meschede’s group[Bonn Univ.]

  13. The single atom trap @ WIPM

  14. Vacuum system dichromatic mirror 830/852nm Filter 780nmfluor. MOT laser Single Atom Trap @ WIPM experimental setup 87Rb MOT 780nm dipole trapping 830/852nm

  15. Fluorescence of a single Rb atom (2009/02/13) 1 atom 0 atom 10s 2 atom 1 atom 0 atom

  16. Hanbury Brown and Twiss (HB-T) effect classical field non-classical thermal coherent single photon Fluorescence of single atom, antibunching: http://en.wikipedia.org/wiki/Hanbury-Brown_and_Twiss_effect M.O.Scully and M.S.Zubairy, Quantum Optics, CUP 1997, P.307

  17. TTL BS Fiber SPCM Discriminator NIM SPCM Trigger Δt Discriminator TTL NIM Single Atom HBT Experiment Coincidence SPCM： EG&G SPCM-AQRH-14-FC Discriminator：ORTEC 935（Quad 200-MHz Constant-Fraction Discriminator） Coincidence： RoentDek TDC8HP

  18. HBT measurement of single atom in dipole trap 18.4mw@830nm 2.28mw@Cooling 0.80mw@Repump AC shift 39MHz U01.9mK Rabi Freq 0 26.6MHz（RL） 33.7MHz（CL22） 79 MHz（CL23） 107 total events 103 coincidence Photon antibunching (single atom)

  19. lifetime of the single atom trap Time sequence threshold Counting 1) once counting > threshold, freezing the trap; 2) waiting a time Δt, then check; repeat 100 times; 3) new Δt, then repeat. ∥ Δt ∥ ON OFF Cooling and repump laser 50ms ∥ ON OFF MOTmagnetic field ∥ ON OFF Counting clock ON OFF Dipole trap laser

  20. Lifetime 468ms with MOT on Lifetime 11s with MOT off

  21. Ring Optical Latticesby SLM

  22. Laguerre-Gaussian Mode

  23. Ring Optical Lattice (ROL) Superposition of the mode

  24. Realizing ROLwith a spatial light modulator (SLM) SLM

  25. 0th order 1th order modulated

  26. Trapping atom array with ROL Single trap Double trap Spatial filter

  27. Rotating the ROL

  28. Rotating ROL Scheme 1: max 60Hz Continuous phase pattern animation on the SLM, max refresh rate 60Hz

  29. Scheme 2: up to MHz (EOM driven phase change) 2Hz rotation is shown here

  30. single atoms in rotating ROL Rotating ROL @12Hz with 1 atom Rotating ROL @6Hz with 2 atoms Xiaodong He, Peng Xu, Jin Wang and Mingsheng Zhan, Opt.Express （accpted, 2009)

  31. Dynamics of single atoms in the traps

  32. Loading two atoms to a trap Ring trap Gaussian trap

  33. Light assisted nonelastic collisions of two atoms in a trap In a Ring trap Collisions rare Difficult to meet 2 atoms remain In a Gaussian trap 0 atom Collisions rich Easier to meet 1 atom MOT light on

  34. Splitting a trap (with an atom) to two traps or Potential or force? (single vs multi: collision) Particle or wave packet? (single atom interferometer)

  35. Figure 12. Axial insertion. An atom trapped in one of the potential wells of the standing wave of theVDT is inserted into the Gaussian potential well of the HDT by axially moving the VDT along the z-direction. Figure 13. Radial insertion of an atom. (a) An atom in the VDT after the extraction. The traps are separated by displacing the HDT along the x-direction. (b) The atom in the VDT is transported to the z-position of the HDT. (c) The traps are merged by moving the HDT along the x-direction towards the VDT. d) Evolution of the radial potentials of the traps along the x-axis for steps (b) and (c). Y Miroshnychenko et al., NewJ.Phys.8(2006)191

  36. Moving trap Static trap ? dichroic mirror Static trap fluorescence Moving trap To SPCM PZT PZT scan speed: 10um/40ms 160ms ∥ ∥ Cooling&Repump 80ms 5V PZT ∥ ∥ -2V The depth of the moving well affects the rate carrying the atom

  37. Time evolution of the trap intensity profile Initial ? The final position of the atom is determined by force not the depth of potential. exposure time 1ms readout time 2.5ms

  38. Atom transfer between traps Gaussian trap Merging Splitting ring trap

  39. Time sequence: double  Gaussian  double On Interaction time: N*1/60 s N =1,2,3 …variable Cooling light repumping light MOT coil Off

  40. Time sequence: double  ring  double On Interaction time:N*1/60 s N =1,2,3 …variable Cooling light repumping light MOT coil + L (or – L) SLM light Off

  41. 2 1 Single atom transport（via a Gaussian trap） 1/60 s 3/60 s

  42. Single atom transport（via a ring trap） 2 1 1/60 s 3/60 s

  43. Next … • cooling atom to ground state + internal state control • making interaction of atoms in/between sites • entanglement, quantum simulation / computing …… • single atom AI, HBT…

  44. a way to bring the atoms closer—— optical vector beam (OVB)

  45. Optical vector beam（OVB） • The focused pattern can be much smaller than the diffraction limit Tailoring of arbitrary optical vector beams New Journal of Physics 9 (2007) 78 Phys. Rev. Lett. 91, 233901 (2003) Phys. Rev. Lett. 100, 123904 (2008)

  46. Experimental Arrangement HW PW to trap PBS SLM HW HW Dipole trap laser

  47. Primary results with OVB OVB trap Lifetime longer Tighter potential Normal ring trap Lifetime shorter

  48. Acknowledgments 许鹏 何晓东 王谨 刘敏 Ministry of Sci & Tech of China (MOST) Chinese Academy of Sciences (CAS) Natural Science Foundation of China (NSFC) All of you, for your attention!

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