Nonadditivity of quantum and classical capacities for entanglement breaking multiple-access channels and butterfly network

TL;DR

This paper demonstrates that quantum and classical capacities can exhibit superadditivity in entanglement-breaking quantum networks, especially under high noise, revealing new insights into quantum network capabilities.

Contribution

It shows the first qualitative distinction between superadditivity in bipartite and multipartite quantum systems within entanglement-breaking networks.

Findings

Superadditivity of capacity regions in quantum multiple-access channels

Superadditivity in quantum butterfly networks

Effects are prominent at high noise levels

Abstract

We analyze quantum network primitives which are entanglement-breaking. We show superadditivity of quantum and classical capacity regions for quantum multiple-access channel and quantum butterfly network. Since the effects are especially visible at high noise they suggest that quantum information effects may be particularly helpful in the case of the networks with occasional high noise rates. To our knowledge the present effects provide the first qualitative borderline between superadditivities of bipartite and multipartite systems.