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Quantum Channels Communication Theory

A Mirror-Descent Algorithm for Computing the Petz-Rényi Capacity of Classical-Quantum Channels

arXiv
Authors: Yu-Hong Lai, Hao-Chung Cheng

Year

2026

Paper ID

3749

Status

Preprint

Abstract Read

~2 min

Abstract Words

90

Citations

N/A

Abstract

We study the computation of the α-Rényi capacity of a classical-quantum (c-q) channel for αin(0,1). We propose an exponentiated-gradient (mirror descent) iteration that generalizes the Blahut-Arimoto algorithm. Our analysis establishes relative smoothness with respect to the entropy geometry, guaranteeing a global sublinear convergence of the objective values. Furthermore, under a natural tangent-space nondegeneracy condition (and a mild spectral lower bound in one regime), we prove local linear (geometric) convergence in Kullback-Leibler divergence on a truncated probability simplex, with an explicit contraction factor once the local curvature constants are bounded.

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  • This paper contributes to the Quantum Channels & Communication Theory research area in the Quantum Articles archive.
  • It adds a 2026 reference point for readers tracking recent quantum research.
  • We study the computation of the α-Rényi capacity of a classical-quantum (c-q) channel for αin(0,1).

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