A quantum channel with additive minimum output entropy

Abstract

We give a direct proof of the additivity of the minimum output entropy of a particular quantum channel which breaks the multiplicativity conjecture. This yields additivity of the classical capacity of this channel, a result obtained by a different method by Matsumoto and Yura [quant-ph/0306009]. Our proof relies heavily upon certain concavity properties of the output entropy which are of independent interest.

15 pages, 2 figures

Cited by in corpus (2)

• Additivity of minimal entropy output for a class of covariant channels
• Qubit Channels Which Require Four Inputs to Achieve Capacity: Implications for Additivity Conjectures