弱测量在提高量子参数估计精度中的应用

摘要

Quantum metrology concerns how to achieve the highest precision of physical parameters by quantum re-sources, which has broad applications in many fields. For closed quantum systems, the accuracy attained with entangled quantum probes can significantly surmount that of classical strategies. However, when noises such as decoherence are tak-en into account, the quantum gain may be jeopardized. In this paper, weak measurement is adopted to improve estimation precision in the presence of amplitude-damping decoherence, and it is demonstrated that the method of weak measurement can recover estimation precision to the Heisenberg limit, even though the success probability is in a exponential attenuation. Furthermore, the effectiveness of weak measurement in improving the estimation precision is investigated when ancillary systems are implemented.%量子参数估计理论主要研究如何利用量子资源来提高经典参数的估计精度,其应用非常广泛.对于封闭的量子系统,采用纠缠的量子探针测量未知的经典参数,其估计精度可以大幅地超越经典探针所能达到的精度.然而,当退相干效应存在时,量子探针的优越性就会受到限制.本文引入弱测量的方法提高噪声环境下参数估计的精度,并证明了当退振幅噪声存在时,这一方法可以使得参数估计的精度恢复到海森堡极限,尽管实现的概率会随着探针个数的增加呈指数地减少.本文进一步考察了当辅助系统存在时,弱测量的方法对提高参数估计精度的有效性.