恒元物理学讲座（第088期）：Multipartite Gaussian steering: Monogamy constraints and quantum cryptography applications

讲座内容：The concept of quantum steering was originally introduced bySchrödinger to describe the “spooky action-at-a-distance” effect noted in theEinstein-Podolsky-Rosen (EPR) paradox, whereby local measurements performed onone party apparently adjust (steer) the state of another distant party. Weextend to study multipartite steering distributed over many parties. First, wederived inequalities to demonstrate multipartite EPR steering [1] which hasbeen experimentally tested with optical network up to eight modes [2]. Second,we derived laws for the distribution of quantum steering among differentparties in multipartite Gaussian states under Gaussian measurements [3]. Veryrecently, the monogamy relations for Gaussian steerability have beendemonstrated for four-mode square Gaussian cluster state [4]. Our results pindown the role of multipartite steering for quantum communication.

[1] Q. Y. He & M. D. Reid, Phys. Rev. Lett. 111, 250403 (2013).

[2] S. Armstrong et al., Nature Physics 11, 167-172 (2015).

[3] Y. Xiang et al., Phys. Rev. A 95, 010101R (2017).

[4] X. W. Deng et al., Phys. Rev. Lett. 118, 230501 (2017).