Coherent Communication of Classical Messages

TL;DR

This work defines coherent communication in terms of a simple primitive, shows it is equivalent to the ability to send a classical message with a unitary or isometric operation, and uses it to relate other resources in quantum information theory.

Abstract

We define "coherent communication" in terms of a simple primitive, show it is equivalent to the ability to send a classical message with a unitary or isometric operation, and use it to relate other resources in quantum information theory. Using coherent communication, we are able to generalize super-dense coding to prepare arbitrary quantum states instead of only classical messages. We also derive single-letter formulae for the classical and quantum capacities of a bipartite unitary gate assisted by an arbitrary fixed amount of entanglement per use.

Theorems & Definitions (5)

• Proposition 1
• Lemma 2: coherent HSW
• Corollary 3: RSP capacity of unitary gates
• Corollary 4
• Proposition 5