Presented by:
Felix Leditzky
Date:
Thursday 26th July 2018 - 11:45 to 12:30
Venue:
INI Seminar Room 1
Abstract:
The quantum
capacity of a quantum channel captures its capability for noiseless quantum
communication. It lies at the heart of quantum information theory.
Unfortunately, our poor understanding of nonadditivity of coherent information
makes it hard to understand the quantum capacity of all but very special
channels. In this paper, we consider the dephrasure channel, which is the
concatenation of a dephasing channel and an erasure channel. This very simple
channel displays remarkably rich and exotic properties: we find nonadditivity
of coherent information at the two-letter level, a substantial gap between the
threshold for zero quantum capacity and zero single-letter coherent
information, a big gap between single-letter coherent and private informations.
Its clean form simplifies the evaluation of coherent information substantially
and, as such, we hope that the dephrasure channel will provide a much-needed
laboratory for the testing of new ideas about nonadditivity.
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