Almost all quantum states have nonclassical correlations

A. Ferraro, L. Aolita, D. Cavalcanti, F.M. Cucchietti, A. Acín

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494 Citations (Scopus)
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Quantum discord quantifies nonclassical correlations in a quantum system including those not captured by entanglement. Thus, only states with zero discord exhibit strictly classical correlations. We prove that these states are negligible in the whole Hilbert space: typically a state picked out at random has positive discord and, given a state with zero discord, a generic arbitrarily small perturbation drives it to a positive-discord state. These results hold for any Hilbert-space dimension and have direct implications for quantum computation and for the foundations of the theory of open systems. In addition, we provide a simple necessary criterion for zero quantum discord. Finally, we show that, for almost all positive-discord states, an arbitrary Markovian evolution cannot lead to a sudden, permanent vanishing of discord.
Original languageEnglish
Article number052318
Number of pages6
JournalPhysical Review A (Atomic, Molecular, and Optical Physics)
Issue number5
Publication statusPublished - 17 May 2010

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