Universal superposition codes: capacity regions of compound quantum broadcast channel with confidential messages

TL;DR

This paper develops universal superposition codes for compound quantum broadcast channels, enabling reliable transmission of broadcast and confidential messages despite channel uncertainties, and characterizes their capacity regions.

Contribution

It introduces a universal superposition coding scheme for compound quantum broadcast channels, extending random coding techniques to handle channel uncertainties.

Findings

Derived universal codes robust to channel variations.

Provided a multi-letter capacity region characterization.

Applicable to transmitting both public and confidential messages.

Abstract

We derive universal codes for transmission of broadcast and confidential messages over classical-quantum-quantum and fully quantum channels. These codes are robust to channel uncertainties considered in the compound model. To construct these codes we generalize random codes for transmission of public messages, to derive a universal superposition coding for the compound quantum broadcast channel. As an application, we give a multi-letter characterization of regions corresponding to the capacity of the compound quantum broadcast channel for transmitting broadcast and confidential messages simultaneously. This is done for two types of broadcast messages, one called public and the other common.