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Covariance, correlation and entanglement

R I A Davis, R Delbourgo, P D Jarvis

quant-pharXiv:quant-ph/0001076

Abstract

Some new identities for quantum variance and covariance involving commutators are presented, in which the density matrix and the operators are treated symmetrically. A measure of entanglement is proposed for bipartite systems, based on covariance. This works for two- and three-component systems but produces ambiguities for multicomponent systems of composite dimension. Its relationship to angular momentum dispersion for symmetric symmetric spin states is described.

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