0410050v5

related topics
{state, states, entangled}
{entanglement, phys, rev}
{energy, gaussian, time}
{state, states, coherent}
{bell, inequality, local}
{information, entropy, channel}

Continuous variable tangle, monogamy inequality, and entanglement sharing in Gaussian states of continuous variable systems

Gerardo Adesso, Fabrizio Illuminati

abstract: For continuous-variable systems, we introduce a measure of entanglement, the continuous variable tangle ({\em contangle}), with the purpose of quantifying the distributed (shared) entanglement in multimode, multipartite Gaussian states. This is achieved by a proper convex roof extension of the squared logarithmic negativity. We prove that the contangle satisfies the Coffman-Kundu-Wootters monogamy inequality in all three--mode Gaussian states, and in all fully symmetric $N$--mode Gaussian states, for arbitrary $N$. For three--mode pure states we prove that the residual entanglement is a genuine tripartite entanglement monotone under Gaussian local operations and classical communication. We show that pure, symmetric three--mode Gaussian states allow a promiscuous entanglement sharing, having both maximum tripartite residual entanglement and maximum couplewise entanglement between any pair of modes. These states are thus simultaneous continuous-variable analogs of both the GHZ and the $W$ states of three qubits: in continuous-variable systems monogamy does not prevent promiscuity, and the inequivalence between different classes of maximally entangled states, holding for systems of three or more qubits, is removed.

oai_identifier:
oai:arXiv.org:quant-ph/0410050
categories:
quant-ph cond-mat.other math-ph math.MP physics.optics
comments:
13 pages, 1 figure. Replaced with published version
doi:
10.1088/1367-2630/8/1/015
arxiv_id:
quant-ph/0410050
journal_ref:
New J. Phys. 8, 15 (2006)
created:
2004-10-06
updated:
2006-02-02

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