Channel capacities in quantum networks

Abstract

This thesis considers a quantum network scenario where multiple parties share entangled states and aims to establish network communication. We focus on entanglement-assisted network channels for two-sender and two-receiver interference channels and two-sender and one-receiver multiple access channels. We characterize types of noise that may occur in two-input and two-outcome nonlocal games. We show that network coding with nonlocal correlations can enhance channel capacities more than capacities with local resources. We then consider various network channels where noise appears with the Clauser-Horne-Shimony-Holt (CHSH) game and show a hierarchy in channel capacities according to resources exploited in network codings, such as non-signaling, quantum, and local resources. Optimal cooperation strategies with quantum resources are explicitly constructed. We also present a suboptimal cooperation strategy that circumvents optimization steps but contains a depolarization protocol to share isotropic correlations. Our results are readily applied to efficient network coding in a quantum network.