Disorder overtakes Order in Information Concentration over Quantum Networks

Physical Review A (Impact Factor: 2.99). 06/2011; 84(4). DOI: 10.1103/PhysRevA.84.042334
Source: arXiv

ABSTRACT We consider different classes of quenched disordered quantum XY spin chains,
including quantum XY spin glass and quantum XY model with a random transverse
field, and investigate the behavior of genuine multiparty entanglement in the
ground states of these models. We find that there are distinct ranges of the
disorder parameter that gives rise to a higher genuine multiparty entanglement
than in the corresponding systems without disorder -- an order-from-disorder in
genuine multiparty entanglement. Moreover, we show that such a disorder-induced
advantage in the genuine multiparty entanglement is useful -- it is almost
certainly accompanied by a order-from-disorder for a multiport quantum dense
coding capacity with the same ground state used as a multiport quantum network.

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    ABSTRACT: There are two important paradigms for defining quantum correlations in quantum information theory, viz. the information-theoretic and the entanglement-separability ones. We find an analytical relation between two measures of quantum correlations, one in each paradigm, and show that only a certain cone-like region on the two-dimensional space spanned by these measures is accessible to pure three-qubit states. The information-theoretic multiparty quantum correlation measure is related to the monogamy considerations of a bipartite information-theoretic quantum correlation measure, while the entanglement-separability multiparty measure is the generalized geometric measure, a genuine multiparty entanglement measure. We also find an analytical relation between two multiparty entanglement measures, and again obtain a cone-like accessible region in this case. One of the multisite measures in this case is related to the monogamy of a bipartite entanglement measure, while the other is again the generalized geometric measure.
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    ABSTRACT: We investigate the behavior of genuine multipartite entanglement of paradigmatic frustrated quantum spin systems. We consider six different spin models, whose frustration ranges from being very high to very low. We find that the highly frustrated quantum spin systems are near-maximally genuine multipartite entangled, while those with low frustration do not possess a similar definite behavior with regard to their genuine multipartite entanglement.
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    ABSTRACT: We investigate the behavior of a genuine multiparticle entanglement, viz. the generalized geometric measure, in gapless-to-gapped quantum transitions of one-dimensional and two-dimensional spin models.The investigations are performed in the exactly solvable one-dimensional XY models, as well as two-dimensional frustrated J1-J2 models, including the Shastry-Sutherland model. In particular, we find that multiparty entanglement acts as a better tool than the bipartite one in detecting such transitions in the frustrated quantum systems.

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