Quantum key distribution is a cornerstone of quantum technology, offering information-theoretical secure keys for remote parties. With many quantum communication networks established globally, the mode-pairing protocol stands out for its efficacy over inter-city distances using simple setups, emerging as a promising solution. In this study, we employ the mode-pairing scheme into existing inter-city fiber links, conducting field tests across distances ranging from tens to about a hundred kilometers. Our system achieves a key rate of 1.217 kbit/s in a 195.85 km symmetric link and 3.089 kbit/s in a 127.92 km asymmetric link without global phase locking. The results demonstrate that the mode-pairing protocol can achieve key rates comparable to those of a single quantum link between two trusted nodes on the Beijing-Shanghai backbone line, effectively reducing the need for half of the trusted nodes. These field tests confirm the mode-pairing scheme’s adaptability, efficiency, and practicality, positioning it as a highly suitable protocol for quantum networks.

中文翻译：

---

模式配对量子密钥分发现场测试


量子密钥分发是量子技术的基石，为远程各方提供信息论安全密钥。随着全球范围内建立了许多量子通信网络，模式配对协议因其使用简单设置在城际距离上的功效而脱颖而出，成为一种有前景的解决方案。在这项研究中，我们将模式配对方案应用到现有的城际光纤链路中，在数十到大约一百公里的距离内进行现场测试。我们的系统在没有全局锁相的情况下，在 195.85 km 对称链路中实现了 1.217 kbit/s 的关键速率，在 127.92 km 非对称链路中实现了 3.089 kbit/s 的关键速率。结果表明，模式配对协议可以实现与京沪骨干线上两个可信节点之间的单量子链路相当的关键速率，有效减少对一半可信节点的需求。这些现场测试证实了模式配对方案的适应性、效率和实用性，将其定位为非常适合量子网络的协议。