北京雁栖湖应用数学研究院 北京雁栖湖应用数学研究院

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关于我们
院长致辞
理事会
协作机构
参观来访
人员
管理层
科研人员
博士后
来访学者
行政团队
学术研究
研究团队
公开课
讨论班
招生招聘
教研人员
博士后
学生
会议
学术会议
工作坊
论坛
学院生活
住宿
交通
配套设施
周边旅游
新闻
新闻动态
通知公告
资料下载
清华大学 "求真书院"
清华大学丘成桐数学科学中心
清华三亚国际数学论坛
上海数学与交叉学科研究院
BIMSA > BIMSA Lecture Direct measurement of density matrix without ancillary pointers
Direct measurement of density matrix without ancillary pointers
组织者
王宇
演讲者
冯田峰
时间
2023年09月07日 20:00 至 21:30
地点
A3-2-301
摘要
A direct measurement protocol allows reconstructing specific elements of the density matrix of a quantum state without using quantum state tomography. However, the direct measurement protocols to date are primarily based on weak or strong measurements with an ancillary pointer, which interacts with the investigated system to extract information about the specified elements. In this talk, I will review previous protocol of direct measurement and introduce a direct measurement scheme based on phase-shifting operations which do not need ancillary pointers. In this method, estimates of at most six expectation values of projective observables suffice to determine any specific element of an unknown quantum density matrix. A concrete quantum circuit to implement this direct measurement protocol for multiqubit states is provided, which is composed of just single-qubit gates and two multiqubit controlled-phase gates. This scheme is also extended for the direct measurement of the density matrix of continuous-variable quantum states. It is shown that the method can be used in quantum information applications where only partial information about the quantum state needs to be extracted, for example, problems such as entanglement witnessing, fidelity estimation of quantum systems, and quantum coherence estimation.
演讲者介绍
Tianfeng Feng is a postdoctoral fellow at the University of Hong Kong. He focuses on theories and experiments related to quantum information processing and quantum foundations, and has published more than 10 papers in high-impact journals, including Phys. Rev. D, npj Quantum Information, Photonics Research, Phys. Rev. A, etc.
北京雁栖湖应用数学研究院
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