State redistribution as merging: introducing the coherent relay

TL;DR

This paper introduces a new protocol called the coherent relay, which simplifies quantum state redistribution by deriving it from coherent state-merging, enabling more efficient quantum communication with fewer resources.

Contribution

The paper presents a novel protocol that uses state merging to facilitate quantum state redistribution via a relay, unifying several quantum communication primitives.

Findings

Derived state redistribution from coherent state-merging.

Introduced the coherent relay protocol for efficient quantum state transfer.

Reduced classical communication in partial state-merging through ebit repackaging.

Abstract

State redistribution allows one party to optimally send part of her state to another party. Here we show that this can be derived simply from two applications of coherent state-merging. This provides a protocol whereby a middle party acts as a relay station to help another party more efficiently transfer quantum states. This also gives a protocol for state splitting and the reverse Shannon theorem (assisted or unassisted by side information), and allows one to use less classical communication for partial state-merging using a sub-protocol we call ebit repackaging. Thus state-merging generates the other primitives of quantum communication theory, reducing the hierarchy between members of the first family of quantum protocols.