Observation of BEC in the Tight Binding Limit and Quantum Optics Research in SIOM of CAS

1. Observation of BEC in the Tight Binding Limit and Quantum Optics Research in SIOM of CAS Wang Yu-zhu Key Laboratory for Quantum Optics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Workshop on Atomic Bose-Einstein Condensates Celebrating the Einstein Year of Physics Beijing, Nov. 23th, 2005

2. Nembers of our groups: Liu Liang, (Prof.), He Huijuan, (Prof.) Hu Zhengfen(Asoc.Prof.), Fu Haixiang (Asoc.Prof.), Zhou Shuyu, Wei Rong, Den Janliao, Liao Jun, Cheng Huadong, Xu Zhen, Lv Deshang, Qu Qiuzhi, Li Tian, Xu Xinping, Zhang Wentao, Li Xiaolin, Ke Ming, Bian Fengang, Zhang Ponfei, Ma Yisheng, Ma Hongyu, zhang Yu. Den Lu(US), Long Quan(US),Yin Jianping,Hong Tao(US), Lv Baolong, Li Yongqing,Wang Xinqi , Xu Xinye(US).

3. Identify the formation of a Bose-Einstein condensate in tight confinement. • Study of Atom Chip with cold atoms. • Study of cold atomic clock (Space clock). • 4. Superluminal and slow light propagation in gas medium.

4. Experimental set-up of BEC

5. Quadrupole Ioffe Configuration (QUIC) Magnetic Trap Heansch’s group proposed QUIC trap

7. Identify the formation of a Bose-Einstein condensate : • (1) The sudden increase in the density of the cloud. • (2) The sudden appearance of a bimodal cloud consisting of a diffuse normal component and a dense core (the condensate). • (3) The velocity distribution of the condensate was anisotropic in contrast to the isotropic expansion of the normal (non-condensed) component. • (4) The good agreement between the predicted and measured transition temperatures.

8. The sudden appearance of a bimodal cloud consisting of a diffuse normal component and a dense core (the condensate). B=5G B=0.5G

9. Everyone engaged in practical work must investigate conditions at the lower levels 3 July 2002 We have just received the following report of production of a Bose-Einstein condensate in Shanghai: BEC in 87Rb has been achieved at the Laboratory for Quantum Optics in the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences. The first evidence of quantum phase transition after rf-evaporation cooling was observed on the 19th of March 2002. After some improvement of our imaging system and magnetic current power, the bimodal distribution of atom cloud can be now seen more clearly and repeatedly. Our experimental details: we employ a standard double vacuum-chamber system. Cold atoms collected in the upper MOT are continuously loaded into the lower MOT by light pressure force. Within 15 s, about 6 x 108 atoms are trapped in the lower MOT with a temperature 210 microKelvin. Then the transferring light is cut off and a 5-10 ms optical molasses cooling is applied. After that 3 x 108 atoms are left with a temperature 20 microKelvin. In about 2 ms atoms are optically pumped onto a weak-field-seeker state, and loaded into a quadrupole magnetic trap with an efficiency of about 30%. Then atoms are compressed by ramping up the magnitude of quadrupole trap, and the atomic temperature increases to 150 microKelvin. Atoms are then adiabatically transferred to a QUIC trap in 1-2s. About 1 x 108 atoms are detected in QUIC trap and the lifetime of atoms is about 50s. The radial and axial oscillation frequencies are 150Hz and 14Hz, respectively. The bias magnetic field is 5.4 Gauss. By logarithmically scanning rf frequency from 15 MHz to 3.77 MHz in 19 s and waiting for 100 ms re-thermalization, the absorption image of atom cloud is detected in-situ by a CCD camera. We observe distinct halo appearing around atom cloud near phase transition point, due to the diffraction- limited resolution of imaging system (top frames of figure). To correctly estimate the temperature, we adiabatically ramp down the trap magnitude (with cloud size enlarged and temperature decreased but phase density unchanged) within 1s, pictures are then taken 100 ms after the relaxation (bottom frames of figure.

10. Is it possible to observe the BEC directly by absorption imaging ? M. R. Anderson et al, Science, 273, 84(1996). “We attempted to observe the BEC directly by absorption imaging, but failed because of the high optical density of the atom cloud near the critical temperature” .

11. M. R. Anderson et al, Science, 273, 84(1996). “The effective area of the atomic cloud is approximately linearly related to the temperature. “ “The sudden decrease in area at the onset of the evaporative cooling is a sensitive indicator for the phase transition .”

12. Detection Absorption image of the cloud along X-axis Detection Set-up Special resolution: 15μm Absorption image of the cloud along Y-axis

13. Identification of the phase transition by absorption imaging of the probe beamSudden decreasing of the temperature of the cloud

16. 物质波的超辐射 Experimental results

17. Theoretical results L.You, Maciej Lewenstein,Near-Resonant Imaging of Trapped Cold Atomic Samples,Journal of Research of the National Institute of Stands and Technology,Volume 101,Number 4 July-August 1996; R.J.Glauber, in Lectures in Theoretical Physics, W.E.Brittin and L.G.Dunham, eds,.Vol.I,Interscience,New York(1959)p.315

18. Comparesion of theoretical and experimental Results L.You, Maciej Lewenstein,Near-Resonant Imaging of Trapped Cold Atomic Samples,Journal of Research of the National Institute of Stands and Technology,Volume 101,Number 4 July-August 1996; R.J.Glauber, in Lectures in Theoretical Physics, W.E.Brittin and L.G.Dunham, eds,.Vol.I,Interscience,New York(1959)p.315

19. New QUIC magnetic trap I =25A o ,

20. T=320nk

21. t=6ms t =10ms t=17 ms t=18 ms T<150nK Tc=220nK

22. Atom Chip • 1.H-atom chip study • 2.RF atom chip

23. The first Chinese atom chip

24. MOT Coil I Bias-Coil Si Base I I (Gold thin film） detection I Trapping beam Periodic magnetic microtraps experiment process

25. Experimental set-up of the atom chip MOT to trap cold atoms for the chip

26. Cold atom number N= in the MOT 1x106 Cold atom number N= in the MOT on the chip 1x105

27. Atom Chip-a RF magnetic trap of cold atoms

28. Magnetic trap can confine atoms in weak-field seeking states, the atoms are susceptible to two-body hyperfine or Zeeman level exchanging collisions. We proposed an ac magnetic field trap, which is based on the interaction of magnetic dipole moment of atom with both ac quadurpole magnetic field and a dc magnetic field. Lifang Xu, Jianping Yin and Yuzhu Wang,Optics Commun., 188,93(2001) "A proposal for ac magnetic guide and trap of cold atoms "

29. RF-magnetic trap

32. RF Signal Y B0 X R.F. ω=26.4MHz R. Current I=1.5A Bias field B0=2.1Gauss Deep of the trap 200μK RF Signal

33. RF-Atomchip Program Collaborator: Prof Jiuyao Tang Department of Physics, Zhejiang University Prof Weijia Wen Department of Physics, Hongkong University of Science and Technology

34. Picture of the RF-atom chip

35. Interference of mater wave Beam splitter

36. 原子喷泉研究 ( Atomic fountain clock) Purpose of the research: To build a movable atomic clock . To develop technique of space atomic clock. Paris Observatory

37. Probe type of an atomic fountain clock

38. Probe type of the movable atomic fountain clock. Vacuum in the chamber: p~5x10(-10)Torr.

39. Micro-wave cavity

40. Measurement of the Q factor 在微波中心频率的右边，微波功率下降2.95dB时，频率偏差为190kHz。 这样可以看出微波腔的带宽大约为380kHz。微波腔的有载Q值为17986。

41. 选态腔: 微波功率下降3.00dB时，频率偏差为840kHz。微波腔的有载Q值为4298.5。

42. Measurem-ent of the residual magnetic field in thevacuum chamber.∆B < 10nG

43. High of lunching 50-80cm

46. Superluminal propagation

47. Hanle 组态 (Hanle configuration)

49. EITand EIA Superluminal light： 5P1/ 2 -2 -1 0 1 2 m f 5P1/ 2 -2 -1 0 1 2 F’=2 -1 0 1 F’=1 Double  dark state： 5S ½ -2 -1 0 1 2 m f F=2 arXiv:quant-ph/0309171 v1 Texas A&M University