Routing entanglement in the quantum internet

TL;DR

This paper introduces advanced protocols for quantum networks that enable high-rate, multi-user entanglement distribution, surpassing traditional linear repeater chains by exploiting network diversity and multiple paths.

Contribution

It develops novel quantum repeater protocols that significantly improve entanglement rates for multiple user pairs simultaneously in quantum networks.

Findings

Protocols enable high-rate entanglement between multiple user pairs.

Exploiting network path diversity yields large entanglement rate gains.

Quantum memories with short coherence times can still significantly impact network performance.

Abstract

Remote quantum entanglement can enable numerous applications including distributed quantum computation, secure communication, and precision sensing. In this paper, we consider how a quantum network-nodes equipped with limited quantum processing capabilities connected via lossy optical links-can distribute high-rate entanglement simultaneously between multiple pairs of users (multiple flows). We develop protocols for such quantum "repeater" nodes, which enable a pair of users to achieve large gains in entanglement rates over using a linear chain of quantum repeaters, by exploiting the diversity of multiple paths in the network. Additionally, we develop repeater protocols that enable multiple user pairs to generate entanglement simultaneously at rates that can far exceed what is possible with repeaters time sharing among assisting individual entanglement flows. Our results suggest that the early-stage development of quantum memories with short coherence times and implementations of probabilistic Bell-state measurements can have a much more profound impact on quantum networks than may be apparent from analyzing linear repeater chains. This framework should spur the development of a general quantum network theory, bringing together quantum memory physics, quantum information theory, and computer network theory.