Quantum discord: a measure of the quantumness of correlations.

By Harold Ollivier, Wojciech H. Zurek. Physical Review Letters, 2001

3,049 citations recorded by the source corpus.

Two classically identical expressions for the mutual information generally differ when the systems involved are quantum. This difference defines the quantum discord. It can be used as a measure of the quantumness of correlations. Separability of the density matrix describing a pair of systems does not guarantee vanishing of the discord, thus showing that absence of entanglement does not imply classicality. We relate this to the quantum superposition principle, and consider the vanishing of discord as a criterion for the preferred effectively classical states of a system, i.e., the pointer states.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/777083abb4cf1e71e0ab6f08a61c1208db787b94

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Citations in the corpus

Observing the operational significance of discord consumption (2012, background): “Depending on context, the class of measurements, M, that we optimize over to obtain J(A|B) is sometimes restricted to only projective measurements [6]; and in the case of continuous variables, sometimes Gaussian measurements [19, 20].”
The role of quantum information in thermodynamics—a topical review (2015, background): “The quantum discord AB I A B I A B : : ( ) ≔ ( ) ( )  r r s, with σ the state after a minimally disturbing measurement on Bob, is a form of quantum correlation weaker than entanglement [227, 228].”
Quantum-enhanced measurements without entanglement (2017, background): “Such correlations are usually referred to under the collective name of quantum discord (Henderson and Vedral, 2001; Ollivier and Zurek, 2001), see also (Adesso et al., 2016; Modi et al., 2012) for recent reviews.”
Quantum Fluctuation Theorems for Arbitrary Environments: Adiabatic and Nonadiabatic Entropy Production (2017, background): “[76, 77], we maximize I(ρSE) over {P∗ m,Qμ}, then the inclusive entropy production is equal to the (symmetric) quantum discord [64, 78] of the state ρSE .”
Dynamics of non-Markovian open quantum systems (2015, background): “In addition, was proven by Rodriguez-Rosario et al. (2008) that initial states with zero discord (Modi et al., 2012a; Ollivier and Zurek, 2001), such as (31), i.e. fulfilling the property [ρs(0) ⊗ 11B , ρtot(0)] = 0, lead to completely positive reduced dynamics.”
Daemonic ergotropy: enhanced work extraction from quantum correlations (2016, background): “(24) with x real and positive, minimizes δW at a fixed value of C.”