Chen Geng, Yin Peng, Zhang Wen-Hao, Li Gong-Chu, Li Chuan-Feng, Guo Guang-Can
CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China.
CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China.
Entropy (Basel). 2021 Mar 16;23(3):354. doi: 10.3390/e23030354.
Weak measurements have been under intensive investigation in both experiment and theory. Numerous experiments have indicated that the amplified meter shift is produced by the post-selection, yielding an improved precision compared to conventional methods. However, this amplification effect comes at the cost of a reduced rate of acquiring data, which leads to an increasing uncertainty to determine the level of meter shift. From this point of view, a number of theoretical works have suggested that weak measurements cannot improve the precision, or even damage the metrology information due to the post-selection. In this review, we give a comprehensive analysis of the weak measurements to justify their positive effect on prompting measurement precision. As a further step, we introduce two modified weak measurement protocols to boost the precision beyond the standard quantum limit. Compared to previous works beating the standard quantum limit, these protocols are free of using entangled or squeezed states. The achieved precision outperforms that of the conventional method by two orders of magnitude and attains a practical Heisenberg scaling up to n=106 photons.
弱测量在实验和理论方面都受到了深入研究。大量实验表明，放大的测量值偏移是由后选择产生的，与传统方法相比，其精度有所提高。然而，这种放大效应是以降低数据采集速率为代价的，这导致确定测量值偏移水平的不确定性增加。从这一角度来看，一些理论研究表明，由于后选择，弱测量无法提高精度，甚至会损害计量信息。在这篇综述中，我们对弱测量进行了全面分析，以证明其对提高测量精度的积极作用。进一步地，我们引入了两种改进的弱测量协议，以将精度提高到超越标准量子极限的水平。与之前突破标准量子极限的研究相比，这些协议无需使用纠缠态或压缩态。所实现的精度比传统方法高出两个数量级，并在光子数n = 106时达到了实际的海森堡标度。
