Developing quantum key distribution (QKD) has been recently directed toward distance extension and network expansion for real-world secure communications. Considering a recent report on a quantum communication network over 4,600 km, it seems that QKD networks using conventional protocols have been sufficiently studied. However, although the twin-field QKD (TF-QKD) proposed for long-distance QKD has been studied deeply enough to succeed the demonstrations over 428- and 511-km deployed fibers, TF-QKD networks have been verified only for a ring network. In this work, we propose a star topological 2 × N TF-QKD network scheme, where the coherence maintenance issue, being the primary obstacle to implementing TF-QKD, can be minimized by the automatic mode-matching feature of the Sagnac-based plug-and-play architecture. A lower number of active controllers is required for our scheme in comparison with one-way TF-QKD networks. Moreover, our scheme adopts a cost-effective configuration that requires only a single pair of single-photon detectors for the entire network system. We conducted a proof-of-concept experiment over a 50-km fiber successfully, achieving an average secret key rate of 1.31 × 10⁻⁴bit per pulse (1.52 bit per second) with the finite-size effect.

开发量子密钥分发 (QKD) 最近已针对现实世界安全通信的距离扩展和网络扩展。考虑到最近关于超过 4,600 公里的量子通信网络的报告，似乎已经对使用传统协议的 QKD 网络进行了充分研究。然而，尽管针对长距离 QKD 提出的双场 QKD (TF-QKD) 已经进行了足够深入的研究，以成功在 428 公里和 511 公里部署的光纤上进行演示，但 TF-QKD 网络仅针对环形网络得到了验证. 在这项工作中，我们提出了星形拓扑 2 ×  NTF-QKD 网络方案中，一致性维护问题是实现 TF-QKD 的主要障碍，可以通过基于 Sagnac 的即插即用架构的自动模式匹配功能来最小化。与单向 TF-QKD 网络相比，我们的方案需要较少数量的活动控制器。此外，我们的方案采用了一种经济高效的配置，整个网络系统只需要一对单光子探测器。^{我们成功地在 50 公里光纤上进行了概念验证实验，在有限尺寸效应下实现了每脉冲 1.31 × 10 -4}比特（每秒 1.52 比特）的平均密钥速率。