How to observe and quantify quantum-discord states via correlations

Matthew A. Hunt; Igor V. Lerner; Igor V. Yurkevich; Yuval Gefen

doi:10.1103/PhysRevA.100.022321

How to observe and quantify quantum-discord states via correlations

Matthew A. Hunt
, Igor V. Lerner
, Igor V. Yurkevich
, Yuval Gefen

University College Birmingham
Weizmann Institute of Science

Research output: Contribution to journal › Article › peer-review

14 Citations (SciVal)

80 Downloads (Pure)

Abstract

Quantum correlations between parts of a composite system most clearly reveal themselves through entanglement. Designing, maintaining, and controlling entangled systems is very demanding, which raises the stakes for understanding the efficacy of entanglement-free, yet quantum correlations, exemplified by quantum discord. Discord is defined via conditional mutual entropies of parts of a composite system and its direct measurement is hardly possible even via full tomographic characterization of the system state. Here we design a simple protocol to detect and quantify quantum discord in an unentangled bipartite system. Our protocol relies on a characteristic of discord that can be extracted from repeated direct measurements of certain correlations between subsystems of the bipartite system. The proposed protocol opens a way of extending experimental studies of discord to electronic systems, but can also be implemented in quantum-optical systems.

Original language	English
Article number	022321
Journal	Physical Review A
Volume	100
Issue number	2
DOIs	https://doi.org/10.1103/PhysRevA.100.022321
Publication status	Published - 16 Aug 2019

Bibliographical note

Funding

This work was supported by the Leverhulme Trust Grants No. RPG-2016-044 (I.V.Y.), No. VP1-2015-005 (I.V.Y., Y.G.), the Italia-Israel project QUANTRA (Y.G.), and the DFG within the network CRC TR 183, C01 (Y.G.). The authors (I.V.L., I.V.Y., and Y.G.) are grateful for the hospitality extended to them at the final stage of this work at the Center for Theoretical Physics of Complex Systems, Daejeon, South Korea. APPENDIX A:

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10.1103/PhysRevA.100.022321

How to observe and quantify quantum-discorded statesAccepted author manuscript, 4.38 MB

https://arxiv.org/abs/1901.11514

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AB - Quantum correlations between parts of a composite system most clearly reveal themselves through entanglement. Designing, maintaining, and controlling entangled systems is very demanding, which raises the stakes for understanding the efficacy of entanglement-free, yet quantum correlations, exemplified by quantum discord. Discord is defined via conditional mutual entropies of parts of a composite system and its direct measurement is hardly possible even via full tomographic characterization of the system state. Here we design a simple protocol to detect and quantify quantum discord in an unentangled bipartite system. Our protocol relies on a characteristic of discord that can be extracted from repeated direct measurements of certain correlations between subsystems of the bipartite system. The proposed protocol opens a way of extending experimental studies of discord to electronic systems, but can also be implemented in quantum-optical systems.

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How to observe and quantify quantum-discord states via correlations

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