基于拉曼量子调控的原子系综集体相干性的研究

During the last ten years, great progress of cold atom research in the areas of precision measurement, quantum communication and quantum memory, has present incomparable scientific value and broad promising applications. Atoms are cooled and trapped around or bellow several micro-Kelvin in ultrahigh vacuum chamber. Laser control of atomic collective state could provide much more sensitive coherence interference than lots of classical mechanism methods and optical techniques, which highly improves measurement accuracy of various physical parameters and offers novel test of foundation of physics. Atomic collective states, as stationary qubits, are also the key component in application of quantum networks and long-distance quantum communication. Yet from validation in a laboratory setting to feasible applications, there are many scientific problems that need to be studied. A key research focus and difficulty for atomic collective state is physical mechanism of collective decoherence and various noise sources of it. Research object of this funding apply is experimental exploration of these decoherence mechanisms, to obtain high visibility of atomic interference and ultra-long coherence lifetime of the atomic collective state. In details, for high precision quantum control of atoms, we would use stimulated Raman laser manipulation to study various noises of atomic collective decoherence, and to find effective methods to shield and diminish all those noises. To pave the way of promising practical application of cold atom in the area of quantum information and precision measurement, is the prime power and ultimate goal of our research.

近十几年冷原子物理在精密测量、量子计算和量子存储等领域的研究和成果，展现出日益显著的科学价值和应用前景。利用激光等对超高真空环境下的冷原子系综进行量子调控，可以得到比许多经典物理方法和纯光学技术等更灵敏的相干干涉，实现各种物理量、物理常数的精密测量和基础物理检验；可以制备和操控量子比特，实现量子网络和量子远距通讯。然而从实验室原理验证走向实际应用，目前还有许多科学问题亟待探索和解决，其中研究的重点和难点之一是原子系综量子态的退相干物理机制及其噪声抑制等。本项目的目标就是探索原子系综集体退相干的物理机制，以实现精密原子干涉和集体量子态的超长相干时间。为此，我们基于受激拉曼激光操控等手段，研究影响原子集体相干态的各种噪声源和退相干机制，进而探索退相干噪声的有效抑制，以实现精密量子调控。让冷原子物理从原理性验证的实验室最终走向量子信息和精密测量等领域的实际应用，是本研究项目的原动力和终极追求。

冷原子物理在量子信息和精密测量等领域具有非常重要的价值。本课题研究基于拉曼量子调控的原子系综集体相干性，研究内容包括两部分，一是寻找制约存储读取效率和相干寿命的物理因素，实现高性能量子存储器，二是搭建小型化冷原子系统探索实现基于拉曼相干调控原子系综的实用化和工程化。项目实施过程中取得的主要进展和实验结果有，1、实现了同时长寿命高效率的光与原子纠缠，存储1秒后贝尔不等式S值为2.36±0.14，仍保持良好的纠缠（尚未发表）；2、基于电磁诱导透明存储方法，观察到约80%的高对比度的梳状透过峰结构（发表于Phys. Rev. A 98, 033802(2018)）；3、基于拉曼调控原子干涉实现了高灵敏度可搬运的原子重力仪样机，灵敏度达到3e-9g/Hz1/2，申请中国国家发明专利6项；4、发现了磁场增强的调制转移光谱稳频方案，极大提高了锁频参考误差信号的信噪比和稳定性（发表于Optics Express 26, 27773-27786(2018)）。上述这些工作对于未来实现冷原子物理从实验室原理性验证走向实际工程应用，是有一定贡献和推动作用的。