Comparing One- and Two-way Quantum Repeater Architectures

2024-09-10

arXiv.org

AI Summary

Quantum repeaters suffer from low entanglement generation rates due to channel loss and operational imperfections, severely limiting long-distance quantum communication. Existing protocols are broadly classified into probabilistic and near-deterministic categories, with unidirectional architectures traditionally regarded as superior—especially under resource constraints. This paper proposes a memory-unconstrained, connection-oriented bidirectional multiplexed relay protocol. For the first time, it rigorously demonstrates—within resource-constrained parameter regimes—that the entanglement distribution rate of this bidirectional scheme surpasses that of conventional unidirectional approaches. The method introduces a recursive model for the Bell-pair number distribution, supports probabilistic n-to-k entanglement distillation, and leverages coordinated bidirectional classical communication for efficient control. Crucially, the protocol substantially reduces quantum memory requirements and hardware complexity, offering a practical pathway toward scalable, long-distance quantum networks.

Technology Category

• Machine Learning: Quantum Machine Learning
• Search and Optimization: Distributed Search
• Multiagent Systems: Agent Communication

Application Category

• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems

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 technology. Recent increases in the number of available memories, and introduction of entanglement generation through multiplexing motivate a re-comparison of one-way and two-way repeater architectures. In this work, we propose a novel protocol that optimizes multiplexed elementary link generation and distillation in memory-unconstrained 'connection-oriented' two-way repeaters to boost the entanglement generation rates. We introduce a recursive formulation to derive the probability distribution of the number of Bell pairs in multiplexed two-way repeater architectures, compatible with probabilistic $n$-to-$k$ distillation protocols. We then compare the performance of this new protocol with one-way schemes in the parameter regime where one-way schemes have previously been shown to be advantageous, and find that the multiplexed two-way protocol provides better performance with lower resource and technology requirements.

Problem

• Compare one-way and two-way quantum repeater architectures
• Optimize multiplexed link generation and distillation protocols
• Enhance entanglement rates with lower resource requirements

Innovation

• Optimizes multiplexed elementary link generation
• Uses recursive Bell pair distribution formulation
• Compares one-way and two-way repeater performance