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学术报告

Discrimination of quantum states under locality constraints in the many-copy setting

俞能昆

（悉尼科技大学）

报告时间： 2021-6-8 10:00-11:00 am

腾讯会议 ID：371 511 728

报告摘要：We study the discrimination of a pair of orthogonal quantum states in the many-copy setting. This is not a problem when arbitrary quantum measurements are allowed, as then the states can be distinguished perfectly even with one copy. However, it becomes highly nontrivial when we consider states of a multipartite system and locality constraints are imposed. We hence focus on the restricted families of measurements such as local operation and classical communication (LOCC), separable operations (SEP), and the positive-partial-transpose operations (PPT) in this paper. We first study asymptotic discrimination of an arbitrary multipartite entangled pure state against its orthogonal complement using LOCC/SEP/PPT measurements. We prove that the incurred optimal average error probability always decays exponentially in the number of copies, by proving upper and lower bounds on the exponent. In the special case of discriminating a maximally entangled state against its orthogonal complement, we determine the explicit expression for the optimal average error probability and the optimal trade-off between the type-I and type-II errors, thus establishing the associated Chernoff, Stein, Hoeffding, and the strong converse exponents. Our technique is based on the idea of using PPT operations to approximate LOCC. Then, we show an infinite separation between SEP and PPT operations by providing a pair of states constructed from an unextendible product basis (UPB): they can be distinguished perfectly by PPT measurements, while the optimal error probability using SEP measurements admits an exponential lower bound. On the technical side, we prove this result by providing a quantitative version of the well-known statement that the tensor product of UPBs is UPB.

报告人简介：俞能昆博士，悉尼科技大学量子软件和信息中心高级讲师。他在2008年和2013年从清华大学计算机科学与技术系分别获得了学士和博士学位。从2014年1月到2016年 7月，他在加拿大滑铁卢大学量子计算研究所做博士后。 2018年，他获得了澳大利亚科学院J G Russell 奖， 并且获得了OOPSLA 2020 和 PLDI 2021 ACM SIGPLAN杰出论文奖。他目前研究兴趣集中在量子计算。

邀请人： 陈霖 石现

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