超冷原子气体在量子精密测量、量子计算和量子信息等方面有重要的实际应用。近期的实验结果表明，利用该体系的量子纠缠和压缩态，有望实现超越标准量子极限的量子精密测量。 本项目拟从实验和理论两方面在旋量玻色－爱因斯坦凝聚中，系统地研究各种噪声（随机磁场、原子损耗、测量误差等）对量子态和量子操作的影响；提出切实可行的噪声抑制方案，提高制备量子纠缠和压缩态的性能，在实验上实现噪声压缩超过标准量子极限10 dB的多体量子纠缠态。并通过系统研究各种实验室噪声对各步骤量子操作过程的实际影响，提出针对性的方案，实现对原子内态的高精度等效分束器和合束器。综合制备的优质量子纠缠和压缩态、高精度的分束器和合束器、噪声免疫的相位积累器、高精度的末态测量等步骤，我们将最终在实验上展示基于超冷原子气体的多模量子干涉效应。本项目的研究为将来开发和设计实用的量子精密测量仪器，奠定关键的实验和理论基础。

Ultracold atomic gases have practical applications in quantum precision measurement, quantum computing, and quantum information science. Recent experimental achievements indicate that quantum precision measurement utilizing quantum entangled and squeezed states of many atoms can exceed the standard quantum limit. In this project, we will investigate both experimentally and theoretically, the effects of various noise sources (such as stray magnetic field, atom loss, and fluctuation in atomic detection) on the preparation and manipulation of quantum states in a spinor atomic Bose-Einstein condensate; We will devise viable experimental protocols to suppress the aforementioned noises such that improved qualities are realized for the prepared quantum entangled and squeezed states in a spinor condensate, with an anticipated squeezing parameter reaching 10 dB below the standard quantum limit. By further investigating noises in real laboratory setting on all related quantum operations and developing targeted protocols to suppress them, we expect to realize high quality analogous internal state matter-wave beam splitters. Integrating all steps discussed above, including the preparation of high quality quantum entangled and squeezed state, high precision beam splitter operation, noise-resistant phase accumulator, and more precise atom detection technique, we will demonstrate multi-mode quantum interference in ultracold atomic gas ensembles. The results obtained in this project will establish a firmer foundation for developing and designing practical devices in quantum science and technologies such as sensors and interferometers of the future.