Comparing One- and Two-way Quantum Repeater Architectures

TL;DR

This paper compares one-way and two-way quantum repeater architectures, demonstrating that two-way repeaters with multiplexing and distillation outperform one-way schemes in performance and resource efficiency.

Contribution

The authors introduce a recursive probabilistic framework for multiplexed two-way repeaters and show their advantages over one-way architectures in large-scale quantum networks.

Findings

Two-way repeaters outperform one-way schemes in key parameters.

The proposed two-way protocol requires lower technological overhead.

Multiplexed two-way architecture achieves higher fidelity and success probability.

Abstract

Quantum repeaters are an essential building block for realizing long-distance quantum communications. However, due to the fragile nature of quantum information, these repeaters suffer from loss and operational errors. Prior works have classified repeaters into three broad categories based on their use of probabilistic or near-deterministic methods to mitigate these errors. Besides differences in classical communication times, these approaches also vary in technological complexity, with near-deterministic methods requiring more advanced hardware. Recent increases in memory availability and advances in multiplexed entanglement generation motivate a fresh comparison of one-way and two-way repeater architectures. In this work, we present a two-way repeater protocol that combines multiplexing with application-aware distillation, designed for a setting where sufficient high-quality memory resources are available -- reflecting architectural assumptions expected in large-scale network deployments. We introduce a recursive formulation to track the full probability distribution of Bell pairs in multiplexed two-way repeater architectures, enabling the performance analysis of multiplexed repeater schemes which use probabilistic $n$-to-$k$ distillation. Using this framework, we compare the proposed two-way protocol with one-way schemes in parameter regimes previously believed to favour the latter, and find that the two-way architecture consistently outperforms one-way protocols while requiring lower technological and resource overheads.