327 research outputs found
Quantum wiretap channel with non-uniform random number and its exponent and equivocation rate of leaked information
A usual code for quantum wiretap channel requires an auxiliary random
variable subject to the perfect uniform distribution. However, it is difficult
to prepare such an auxiliary random variable. We propose a code that requires
only an auxiliary random variable subject to a non-uniform distribution instead
of the perfect uniform distribution. Further, we evaluate the exponential
decreasing rate of leaked information and derive its equivocation rate. For
practical constructions, we also discuss the security when our code consists of
a linear error correcting code
"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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