原子芯片环形物质波导及其相干性研究

Based on the matter-wave interference, atom gyroscope is promising to deliver unprecedented rotational sensitivities, and has potential application prospects in long distance inertial navigation, geophysics research, and fundamental theories. The development of a compact, robust and high sensitivity gyroscope using circular matter waveguide on atom chips, provides the possibility of bringing the atom gyroscope out from the lab into practical engineering. The goal of constructing an atom chip gyroscope has not been achieved yet, the unavoidable requirements is the realization of a smooth and symmetric circular matter waveguide and coherent propagation. Up to now, the major challenge is the elimination of potential imperfection resulting from the input leads. The project aims to develop an atom chip, which employs the vertical input leads and ac modulation, to realize a smooth circular waveguide, and there is no zero magnetic fields along the waveguide center. To load more atoms into the circular waveguide, an optimizing magnetic field transfer scheme is designed based on a macro-H cooper wire structure underneath the atom chip. We apply the standing wave light pluse to achieve the coherent splitting, reflecting and recombining of the ultracold atoms along the circular waveguide, and investigate the coherence properties of the ultracold atoms in detail. The project is of great scientific and practical importance for the development of high sensitivity inertial navigation.

基于物质波干涉的原子陀螺仪可实现高灵敏度的转动测量，在远距离惯性导航、地球物理学研究和基础理论验证等方面具有重要的应用前景。利用原子芯片实现环形物质波导，开展小型化、高稳定度、高灵敏度的原子芯片陀螺仪方案，为原子陀螺仪从实验室步入工程应用化带来更多可能。原子芯片陀螺仪目前尚未实现，关键要产生光滑对称的环形波导，并在波导中实现物质波相干传输。当前面临的难点问题在于消除电流引线导致的环形波导中的势能起伏。本项目拟研制基于垂直引线方式的三环线结构原子芯片，并结合交流调制三环线电流的方法，实现光滑且波导中心无磁场零点的环形波导；基于宏观H型铜导线结构，优化磁阱转移方案，以增加环形波导中的原子数；利用激光驻波脉冲实现环形波导中冷原子云的相干分束、反射及合束，深入探索环形波导中超冷原子的相干特性。本项目研究对实现高精度惯性导航系统具有重要的科学意义和工程应用价值。

本项目结合垂直引线方式的同心三环线结构原子芯片设计和交流调制三环线电流的方法，可产生导引中心无磁场零点的闭合光滑环形波导，有效消除了电流引线导致的环形波导中的势能起伏和原子Majorana跃迁损失。我们在实验上初步突破了硅通孔技术，研制了基于垂直引线方式环形波导的实验性原子芯片。进一步在实验上利用原有的平行引线同心三环线原子芯片验证了交流调制三环线电流可以有效消除环形磁导引中心的磁场零点，并在实验上初步装载了冷原子云。改进原子芯片磁阱转移方案，具体分析了芯片macro-Z阱-micro-Z阱-Dimple阱-环形波导各磁阱转移过程中的磁场分布演化，并优化设计了具体的磁阱转移参数。在实验上优化改造了原有的2D＋ MOT和3D MOT实验系统，实现了2D+ MOT向3D MOT的高效率冷原子输运。并在实验上进一步研究了宏观四极磁阱-芯片微型磁阱-环形波导的磁阱模式匹配问题，优化冷原子云制备和磁阱转移各个过程的实验参数，最终提高了原子转移效率，进一步降低了冷原子云温度。本项目为实现原子芯片陀螺仪打下了坚实的物理基础。