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三维光晶格和原位测量 - 物理所 BEC 研究展望

三维光晶格和原位测量 - 物理所 BEC 研究展望. 王如泉 中国科学院物理研究所 第五届全国冷原子物理和量子信息青年学者学术讨论会 兰州大学 2010. 8. 4. Outline. Why is in situ imaging important The BEC setup at IOP and our in situ imaging plan The 87 Rb- 40 K- 23 Na( 6 Li) project at IOP. BEC – coherent macroscopic matter wave. Matter wave laser

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三维光晶格和原位测量 - 物理所 BEC 研究展望

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  1. 三维光晶格和原位测量-物理所 BEC研究展望 王如泉 中国科学院物理研究所 第五届全国冷原子物理和量子信息青年学者学术讨论会 兰州大学 2010. 8. 4

  2. Outline • Why is in situ imaging important • The BEC setup at IOP and our in situ imaging plan • The 87Rb-40K-23Na(6Li) project at IOP

  3. BEC – coherent macroscopic matter wave Matter wave laser (MPQ group, 2000) Vortex in BEC (JILA group, 2000) BEC of 87Rb (JILA group, 1995) Ideal platform for Ultra low temperature quantum physics lamp laser Matter wave interference (MIT group, 1997)

  4. Quantum simulation of many body physics 什么是量子仿真? 强关联多体物理： 是物理学尚未攻克的难关，又是决定诸多材料物性的关键（铁磁性，巨磁电阻，重费米子，高温超导等） 原因: 多体波函数,全量子系统 非线性系统，无法用微扰论处理 数值仿真 计算资源随系统粒子数指数增长 解决方案之一： 用量子计算机仿真量子系统 新材料探索: 超导, 磁性等 量子计算机: 光晶格中的原子气 基本模型研究: Hubbard模型,Heisenberg模型等 Qi Zhou et al, PRL 103, 085701 (2009) 特殊的量子计算机-量子仿真器

  5. Quantum simulation of many body physics Qi Zhou et al, PRL 103, 085701 (2009)

  6. First quantum simulation experiment looks beautiful, but faces a lot of questions Super fluid to Mott insulator phase transition in 3-D optical lattice Greiner M., Mandel O., Esslinger T., Hansch T. W. & Bloch I., Nature415, 39–44 (2002). 3D optical lattice • Quantum degenerate Bose/Fermi system below micro Kelvin • Optical lattice provide periodical potential with no defects • Atom-atom interaction can be described by a simple s-wave scattering length • Easily tunable Hubbard Model parameters • Artificial toy models: 1D, 2D, spinor, etc • Lack of a clear diagnostic of how to identify phases • Complications due to coexistence of different phases in the same confining potential • Lack of thermometry of the Bose gas in the optical lattice

  7. Time of flight (TOF) imaging

  8. TOF imaging of BEC @ IOP BEC的相变过程 30ms 10ms 0ms 20ms 各向异性膨胀

  9. Problem with TOF measurement Qi Zhou et al, PRL 103, 085701 (2009)

  10. In-situ imaging: corner stone setting experiment by Chin’s group at Chicago Absorption imaging of density profile of thin layer cold atoms in 2-D optical lattice with a high numerical aperture imaging lens. Gemelke, N., Zhang, X., Hung, C.-L. & Chin, Nature, 460, 995 (2009)

  11. I. Bloch’s group’s work to resolve single lattice site I. Bloch et al, Nature, 467, 68(2010)

  12. Melting of a Mott insulator

  13. M. Greiner’s group to achieve single lattice resolution W. S. Bakr, J. I. Gillen, M. Greiner et al, Nature, 462, 74(2009)

  14. Wedding cake structure of the Mott insulator W. S. Bakr, M. Greiner et al, Science, 329, 547(2010)

  15. What can we achieve with in situ imaging of number density Determine the superfluid density, temperature and chemical potential of the trapped system with high accuracy, critical for mapping out the phase diagram at finite temperature Qi Zhou et al, PRL 103, 085701 (2009) Tin-Lun Ho and Qi Zhou，NATURE PHYSICS 6, 131(2009）

  16. Single Chamber BEC @ IOP

  17. Single chamber design vs Double MOT design: advantages and disadvantages

  18. Light-Induced Atomic Desorption for loading a Rubidium Magneto-Optical Trap

  19. MOT loading at different LED current

  20. Vacuum restoring time Fast decay 2s Slow decay 50s

  21. Quadruple trap Phys. Rev. A, 35, 1535(1987)

  22. Magnetic atom transfer belt 冷原子团 转移线圈 Phys. Rev. A, 63, 031401(2001)

  23. Transfer coils geometry 重力方向 保持转移方向的磁场梯度为75G/cm

  24. Field Plot during the transferring process

  25. Transfer coil 3D lattice and Ultra high resolution in situ imaging MOT BEC lattice Imaging lens CCD camera CCD camera

  26. Large numerical aperture long working distance objectives

  27. EMCCD camera Spatial resolved single photon detection

  28. Princeton Instrument ProEM: 512B_eXcelon

  29. Quantum degenerate polar molecules 玻色-费米混合系统（玻色子，费米子到极性分子） 异核偶极分子具有各向异性且长程的偶极-偶极相互作用，是对关联系统研究具有重要意义。 偶极晶体相变，多体偶极量子气，量子信息，超冷化学 量子简并 相干态转化 简并玻色-费米混合系统是得到超冷分子的最优手段 超冷分子的重要科学意义 New. J. Phys., 11, 055049(2009)

  30. Great achievements and current difficulties 激发态冷分子制备 基态冷分子制备 超冷化学中的量子统计特性 • 简并偶极分子实验的关键障碍 • 铷-钾分子偶极矩太小 • 铷-钾分子在超冷碰撞中不稳定 偶极分子的各向异性 Nature, 424, 47(2003), Science, 301, 1510 (2003), Phys. Rev. Lett.100, 143201 (2008). Nature Physics4, 622 (2008), Phys. Rev. Lett.100, 143201 (2008), Science, 322, 231 (2008), Science, 327, 853 (2010), Nature, 464, 1324(2010)

  31. The 87Rb-40K-23Na(6Li) project at IOP 新的原子选择的必要性和优势：40K-23Na 87Rb-40K-23Na（或6Li）混合冷却系统 J. Chem. Phys. 122,204302 (2005) 40K-23Na具有更大的偶极矩和超冷化学反应的稳定性，是所有可能中的最佳组合

  32. Vacuum system 23Na和7Li同一塞曼减速器和同一套染料激光 转移线圈以实现三维光晶格和原位测量 原位测量空间分辨优于2微米 磁阱

  33. Laser cooling system 铷原子冷却激光系统 钾原子冷却激光系统 钠原子冷却激光系统

  34. Cooling laser for Rb and K 25oC下自由运转波长783nm的激光管冷却到-50oC得到767nm，0.2nm/oC。 困难：冷却到-50C热负载很大且有结露问题， 解决方法：真空隔热和三级制冷。

  35. Cooling laser for Lithium

  36. cooling laser for Li

  37. Optic Spectrometer not injection locking FP cavity signal 7mw injection 45°C 8mw injection 45°C Complete injection locking partial injection locking multimode Complete injection locking singlemode 224mw output

  38. 589nm dye laser for Na cooling 半导体激光的波长覆盖 Na冷却所需的589nm激光不能用半导体激光器 成熟的解决方案是染料激光 同时适用于Na(589nm)和Li (671nm)的冷却

  39. Zeeman slower 塞曼减速器： 适合于原子量较小的原子，更好的差分真空泵浦 减速器效能 23Na和7Li的俘获速度不同 但效能和俘获速度无关 23Na和7Li共用塞曼减速器 塞曼减速器轴向磁场优化结果

  40. Atomic transferring belt • 把原子从磁光阱转移到蒸发磁阱 • 为三维光晶格和原位测量等提供可能 • 研制重点： • 复杂的大电流线圈控制电路

  41. Thermal distribution simulation is very important for high performance magnetic trap

  42. Feshbach coils 强磁场1000G 磁场稳定性<50mG(50ppm) 磁场快速扫描G/us 快速开启(ms) 研制重点： 强磁场的获得 超高的磁场稳定性要求 B0=1007.34G, ΔB=170mG Phys. Rev. Lett. 89, 283202 (2002)

  43. Optical lattice 2D 激光器：IPG单频光纤激光器 光功率：50W 束腰: 100 µm 研制重点： 激光的稳定性 超高光路稳定性 3D Nature,453, 736 (2008) Nature physics,1,23(2005)

  44. Thank you for your attention!

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