1,273 research outputs found
Ergodic Classical-Quantum Channels: Structure and Coding Theorems
We consider ergodic causal classical-quantum channels (cq-channels) which
additionally have a decaying input memory. In the first part we develop some
structural properties of ergodic cq-channels and provide equivalent conditions
for ergodicity. In the second part we prove the coding theorem with weak
converse for causal ergodic cq-channels with decaying input memory. Our proof
is based on the possibility to introduce joint input-output state for the
cq-channels and an application of the Shannon-McMillan theorem for ergodic
quantum states. In the last part of the paper it is shown how this result
implies coding theorem for the classical capacity of a class of causal ergodic
quantum channels.Comment: 19 pages, no figures. Final versio
Structure of Optimal Input Covariance Matrices for MIMO Systems with Covariance Feedback under General Correlated Fading
We describe the structure of optimal Input covariance matrices for single
user multiple-input/multiple-output (MIMO) communication system with covariance
feedback and for general correlated fading. Our approach is based on the novel
concept of right commutant and recovers previously derived results for the
Kronecker product models. Conditions are derived which allow a significant
simplification of the optimization problem.Comment: 5 pages, corrected typo
An Ergodic Theorem for the Quantum Relative Entropy
We prove the ergodic version of the quantum Stein's lemma which was
conjectured by Hiai and Petz. The result provides an operational and
statistical interpretation of the quantum relative entropy as a statistical
measure of distinguishability, and contains as a special case the quantum
version of the Shannon-McMillan theorem for ergodic states. A version of the
quantum relative Asymptotic Equipartition Property (AEP) is given.Comment: 19 pages, no figure
MAC Resolvability: First And Second Order Results
Building upon previous work on the relation between secrecy and channel
resolvability, we revisit a secrecy proof for the multiple-access channel from
the perspective of resolvability. We then refine the approach in order to
obtain some novel results on the second-order achievable rates.Comment: Slightly extended version of the paper accepted at the 4th Workshop
on Physical-Layer Methods for Wireless Security during IEEE CNS 2017. v2:
Fixed typos and extended literature section in accordance with reviewers'
recommendation
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