摘要
量子密度矩阵描述了量子态的性质,因此如何有效地测量密度矩阵是量子力学的核心课题之一.最近,几个研究组发展了一种基于弱值的直接测量密度矩阵的方法.相较于常用的量子态层析技术,这种方法能够更直接和更简便地重构密度矩阵.然而这种方法需要耦合额外的测量指针,从而也增加了测量的复杂度和测量系统的设计困难.本文先回顾并讨论了量子态直接测量的相关研究,然后基于δ-淬火直接测量波函数的方法提出了一种新的直接测量密度矩阵的方法.这种方法无需耦合外部测量指针,因此可以降低测量的复杂度和测量系统的设计困难,更进一步地简化了直接测量密度矩阵的实验过程.基于此方法,提出了更高信号强度以及更少操作次数等两种无指针直接测量方案,并对比分析了它们在不同的测量条件下的优缺点.最后,具体设计了测量光子密度矩阵的实验.
Density matrix,which characterizes a quantum state,plays an important role in quantum mechanics.Recently,a method which can directly measure the elements of a density matrix was proposed.Compared with the conventional quantum state tomography which is widely used to reconstruct the density matrix,this measurement method has the advantages of directness and simplicity.However,this direct measurement method relies on an extra pointer space.The addition of this extra pointer can increase the complexity of an experiment.In this paper,we first review previous work on direct measurement,then we propose a scheme to directly measure the density matrix based onδ-quench,which is also a direct measurement method but needs no additional pointer.This proposal reduces the complexity of the measuring system and further simplifies the measurement.We propose two schemes to realize thisδ-quench measurement,then analyse their superiorities in different situations of measurement.An experiment to measure photon’s density matrix is also designed.
作者
温永立
张善超
颜辉
朱诗亮
Wen Yong-Li;Zhang Shan-Chao;Yan Hui;Zhu Shi-Liang(National Laboratory of Solid State Microstructures,School of Physics,Nanjing University,Nanjing 210093,China;Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials,School of Physics and Telecommunication Engineering,South China Normal University,Guangzhou 510006,China;Frontier Research Institute for Physics,Guangdong-Hong Kong Joint Laboratory of Quantum Matter,South China Normal University,Guangzhou 510006,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第11期1-8,共8页
Acta Physica Sinica
基金
广东省重点领域研发计划(批准号:2019B030330001)
广州市科技计划重点项目(批准号:201804020055,2019050001)
国家重点研发计划(批准号:2016YFA0301803)
国家自然科学基金(批准号:12074180)资助的课题。
关键词
量子测量
密度矩阵
直接测量
quantum measurement
density matrix
direct measurement
