量子精密测量中淹没探测噪声的原理与实现

Quantum metrology is an interdiscipline between quantum physics and metrology science, it aims to improve measurement precision via using quantum strategies and quantum resources. However, due to the classical noises from detectors, it is not easy to beat the standard quantum limit (or the shot-noise limit) in a realistic measurement. When the detector noise is larger than the quantum noise, it will dominate the signal and the realistic measurement precision will not reach the optimal limit offered by the quantum resources. In conventional schemes, the measurement precision is improved by decreasing both detector noise and quantum noise. Thus, if the detector noise cannot be decreased in further, the measurement precision cannot be improved via decreasing the quantum noise. By combining the non-Gaussian entangled states and the nonlinear detection, this project will study how to simultaneously submerge the detector noise via increasing the quantum noise and achieve the optimal precision limit via increasing the signal-to-parameter response. The research topics of this project include: the principle of submerging detector noise via increasing quantum noise, the environment effects and the possible experimental realization via ultracold atoms/ions. The successful implementation of this project will not only advance the development of quantum metrology theory, but also provide promising applications in practical quantum sensors.

量子精密测量是量子物理和测量科学的有机结合，主要研究如何利用量子策略和量子资源提高测量精度。然而，要利用量子资源有效地实现突破标准量子极限的精密测量并非易事，当探测器引起的经典噪声大于量子噪声时，探测噪声将主导测量信号的不确定度，使得实际测量精度无法达到量子资源所给出的最优精度极限。传统的量子精密测量方案主要通过同时降低量子噪音和探测噪音来提高测量精度，这意味着，在探测噪音不可进一步改善时，降低量子噪音并不一定能提高测量精度。结合非高斯纠缠态和非线性探测，本项目拟探索通过放大量子噪音去淹没探测噪音，同时尽量放大待估计参数对实验观测量的响应去达到最优精度。主要研究内容包括：放大量子噪音淹没探测噪音的原理、环境效应对信号提取和测量精度的影响、基于实际超冷原子（离子）体系的物理实现。本项目的成功实施，不仅可推动量子精密测量理论的发展和完善，而且对实用量子传感器件的设计有重要的指导价值。

本项目按计划顺利完成，达到了预期的研究目标。本项目主要探索了多体量子纠缠在精密测量的应用中涉及到的一些关键物理问题，研究多体量子干涉与精密测量的基础理论以及新方案。具体包括：研究如何利用量子纠缠提高测量精度，探索如何通过放大量子噪音去淹没探测噪音实现高精度测量，发展如何制备干涉所需的量子纠缠态的新方案，探索退相干、探测噪声等非完美性对物理量测量的影响等。同时，我们发展了有效的数值模拟及解析的方法，分析和揭示了一些新奇的多体量子动力学、拓扑相、拓扑束缚态、拓扑输运等现象，这些理论方法将有助于研究多体量子体系的动力学演化和调控。