Classical capacity and entropy inequalities for generalized amplitude damping
We determine the unassisted classical capacity of every qubit generalized amplitude-damping channel, for all damping strengths and thermal occupations. It equals the one-shot Holevo capacity and is given by a one-variable maximum. A binary pure-state ensemble attains the one-use optimum, and its independent products attain the optimum at every block length. We also prove that one-shot Holevo capacity, minimum output entropy, and regularized unassisted classical capacity are additive under tensor product with every finite-dimensional completely positive trace-preserving partner channel.
Cite
@misc{OAI:Classical-capacity-and-entropy-inequalities-for-generalized-amplitude-damping-September-24-2026,
author = {{OpenAI}},
title = {{Classical capacity and entropy inequalities for generalized amplitude damping}},
howpublished = {OpenAI Math Release preprint
\href{https://github.com/openai/math/blob/main/preprints/Classical-capacity-and-entropy-inequalities-for-generalized-amplitude-damping-September-24-2026/paper.pdf}{OAI:Classical-capacity-and-entropy-inequalities-for-generalized-amplitude-damping-September-24-2026}},
year = {2026}
}