How to observe and quantify quantum-discord states via correlations

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

Research output: Contribution to journalArticlepeer-review


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 languageEnglish
Article number022321
JournalPhysical Review A
Issue number2
Publication statusPublished - 16 Aug 2019

Bibliographical note

© 2019 The American Physical Society


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