Published February 13, 2004 | Version Published
Journal Article Open

Locking Classical Correlations in Quantum States

Abstract

We show that there exist bipartite quantum states which contain a large locked classical correlation that is unlocked by a disproportionately small amount of classical communication. In particular, there are (2n + 1)-qubit states for which a one-bit message doubles the optimal classical mutual information between measurement results on the subsystems, from n/2 bits to n bits. This phenomenon is impossible classically. However, states exhibiting this behavior need not be entangled. We study the range of states exhibiting this phenomenon and bound its magnitude.

Additional Information

© 2004 The American Physical Society (Received 13 March 2003; published 12 February 2004) We thank I. Devetak and C. Bennett for extremely helpful discussions, W. Wootters for enlightening discussion on mutually unbiased bases, and D. Gottesman for a discussion on complete locking. Part of this work was completed while M.H. was visiting at the MSRI program on Quantum Computation. M.H. is supported by EC, Contract No. IST-2001-37559 (RESQ), IST-2001-38877 (QUPRODIS), and also by EQUIP. D.P.DV., J.A.S., and B.M.T. are supported in part by the NSA and the ARDA through ARO Contract No. DAAD19-01-C-0056. D.W. L. acknowledges support from the Tolman Endowment Fund and the NSF under Grant No. EIA-0086038.

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4509
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CaltechAUTHORS:DIVprl04

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2006-08-25
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