Resource theories of communication

TL;DR

This paper introduces a resource theory framework for quantum communication, clarifying debates about the advantages of superposing communication channels and showing that previous criticisms were based on unfair comparisons.

Contribution

It develops a general resource-theoretic framework for quantum communication devices, clarifying the operational distinctions among different superposition strategies.

Findings

Resource theory framework clarifies communication advantages

Superpositions of causal orders are uniquely advantageous

Criticisms based on unfair comparisons are addressed

Abstract

A series of recent works has shown that placing communication channels in a coherent superposition of alternative configurations can boost their ability to transmit information. Instances of this phenomenon are the advantages arising from the use of communication devices in a superposition of alternative causal orders, and those arising from the transmission of information along a superposition of alternative trajectories. The relation among these advantages has been the subject of recent debate, with some authors claiming that the advantages of the superposition of orders could be reproduced, and even surpassed, by other forms of superpositions. To shed light on this debate, we develop a general framework of resource theories of communication. In this framework, the resources are communication devices, and the allowed operations are (a) the placement of communication devices between the communicating parties, and (b) the connection of communication devices with local devices in the parties' laboratories. The allowed operations are required to satisfy the minimal condition that they do not enable communication independently of the devices representing the initial resources. The resource-theoretic analysis reveals that the aforementioned criticisms on the superposition of causal orders were based on an uneven comparison between different types of quantum superpositions, exhibiting different operational features.