210 research outputs found
The asymptotic entanglement cost of preparing a quantum state
We give a detailed proof of the conjecture that the asymptotic entanglement
cost of preparing a bipartite state \rho is equal to the regularized
entanglement of formation of \rho.Comment: 7 pages, no figure
"Pretty strong" converse for the private capacity of degraded quantum wiretap channels
In the vein of the recent "pretty strong" converse for the quantum and
private capacity of degradable quantum channels [Morgan/Winter, IEEE Trans.
Inf. Theory 60(1):317-333, 2014], we use the same techniques, in particular the
calculus of min-entropies, to show a pretty strong converse for the private
capacity of degraded classical-quantum-quantum (cqq-)wiretap channels, which
generalize Wyner's model of the degraded classical wiretap channel.
While the result is not completely tight, leaving some gap between the region
of error and privacy parameters for which the converse bound holds, and a
larger no-go region, it represents a further step towards an understanding of
strong converses of wiretap channels [cf. Hayashi/Tyagi/Watanabe,
arXiv:1410.0443 for the classical case].Comment: 5 pages, 1 figure, IEEEtran.cls. V2 final (conference) version,
accepted for ISIT 2016 (Barcelona, 10-15 July 2016
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