The Gottesman-Kitaev-Preskill (GKP) code, being information theoretically near optimal for quantum communication over Gaussian thermal-loss optical channels, is likely to be the encoding of choice for advanced quantum networks of the future. Quantum repeaters based on GKP-encoded light have been shown to support high end-to-end entanglement rates across large distances despite realistic finite squeezing in GKP code preparation and homodyne detection inefficiencies. Here, we introduce a quantum switch for GKP-qubit-based quantum networks, whose architecture involves multiplexed GKP-qubit-based entanglement link generation with clients, and their all-photonic storage, together enabled by GKP-qubit graph state resources. For bipartite entanglement distribution between clients via entanglement swapping, the switch uses a multi-client generalization of a recently introduced $\textit{entanglement-ranking-based link matching}$ protocol heuristic. Since generating the GKP-qubit graph state resource is hardware intensive, given a total resource budget and an arbitrary layout of clients, we address the question of their optimal allocation towards the different client-pair connections served by the switch such that the sum throughput of the switch is maximized while also being fair in terms of the individual entanglement rates. We illustrate our results for an exemplary data center network, where the data center is a client of a switch and all of its other clients aim to connect to the data center alone -- a scenario that also captures the general case of a gateway router connecting a local area network to a global network. Together with compatible quantum repeaters, our quantum switch provides a way to realize quantum networks of arbitrary topology.

翻译：Gottesman-Kitaev-Preskill(GKP)码在信息论意义上近乎最优地适用于高斯热损耗光学信道上的量子通信，因此很可能成为未来高级量子网络的编码选择。基于GKP编码光的量子中继器已被证明即使在GKP码制备中存在实际有限压缩以及零差探测效率不足的情况下，仍能支持跨越长距离的高端到端纠缠速率。本文介绍了一种面向GKP量子比特量子网络的量子交换机，其架构包含与客户端进行复用的GKP量子比特纠缠链路生成以及全光子存储，这些均由GKP量子比特图态资源实现。为通过纠缠交换在客户端间进行二分纠缠分发，该交换机采用了近期提出的基于纠缠排名的链路匹配协议启发式算法的多客户端推广版本。由于生成GKP量子比特图态资源需要大量硬件投入，在给定总资源预算和任意客户端布局的条件下，我们探讨了如何在交换机服务的不同客户端连接中优化分配资源，以最大化交换机总吞吐量，同时确保各客户端缠绕速率的公平性。我们以典型数据中心网络为例说明结果，其中数据中心作为交换机的一个客户端，其他所有客户端均旨在单独连接数据中心——这一场景也涵盖了将局域网连接至全球网络的网关路由器的通用情形。结合兼容的量子中继器，我们的量子交换机为实现任意拓扑的量子网络提供了可行途径。