With the emergence of the Quantum Internet, the need for advanced quantum networking techniques has significantly risen. Various models of quantum repeaters have been presented, each delineating a unique strategy to ensure quantum communication over long distances. We focus on repeaters that employ entanglement generation and swapping. This revolves around establishing remote end-to-end entanglement through repeaters, a concept we denote as the "quantum-native" repeaters (also called "first-generation" repeaters in some literature). The challenges in routing with quantum-native repeaters arise from probabilistic entanglement generation and restricted coherence time. Current approaches use synchronized time slots to search for entanglement-swapping paths, resulting in inefficiencies. Here, we propose a new set of asynchronous routing protocols for quantum networks by incorporating the idea of maintaining a dynamic topology in a distributed manner, which has been extensively studied in classical routing for lossy networks, such as using a destination-oriented directed acyclic graph (DODAG) or a spanning tree. The protocols update the entanglement-link topology asynchronously, identify optimal entanglement-swapping paths, and preserve unused direct-link entanglements. Our results indicate that asynchronous protocols achieve a larger upper bound with an appropriate setting and significantly higher entanglement rate than existing synchronous approaches, and the rate increases with coherence time, suggesting that it will have a much more profound impact on quantum networks as technology advances.

翻译：随着量子互联网的兴起，先进量子组网技术的需求显著增长。不同类型的量子中继器模型已被提出，每种模型都阐述了确保长距离量子通信的独特策略。我们重点关注采用纠缠生成与交换技术的中继器。这类技术通过中继器建立远程端到端纠缠，我们将其定义为"量子原生"中继器（部分文献中也称为"第一代"中继器）。量子原生中继器路由面临的挑战源于概率性纠缠生成和有限的相干时间。现有方案采用同步时隙搜索纠缠交换路径，导致效率低下。本文提出一套新型异步路由协议，通过引入分布式动态拓扑维护机制（该机制已广泛应用于有损网络的传统路由中，例如采用面向目的地的有向无环图或生成树），为量子网络提供解决方案。该协议异步更新纠缠链路拓扑，识别最优纠缠交换路径，并保留未使用的直接链路纠缠。研究结果表明，在适当参数配置下，异步协议可实现更高的性能上界，其纠缠速率显著优于现有同步方案，且该速率随相干时间增长而提升，这表明随着技术进步，该方案将对量子网络产生更深远的影响。