In-field demonstrations in real-world scenarios boost the development of a rising technology towards its integration in existing infrastructures. Although quantum key distribution (QKD) devices are already adopted outside the laboratories, current field implementations still suffer from high costs and low performances, preventing this emerging technology from a large-scale deployment in telecommunication networks. Here we present a simple, practical and efficient QKD scheme with finite-key analysis, performed over a 21 dB-losses fiber link installed in the metropolitan area of Florence (Italy). Coexistence of quantum and weak classical communication is also demonstrated by transmitting an optical synchronization signal through the same fiber link.

中文翻译：

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佛罗伦萨都会区三态量子密钥分配方案的现场试验

实际场景中的现场演示推动了一项新兴技术的发展，使其与现有基础架构相集成。尽管量子密钥分发（QKD）设备已在实验室外部采用，但当前的现场实施仍遭受高成本和低性能的困扰，从而阻止了这种新兴技术在电信网络中的大规模部署。在这里，我们介绍了一种简单，实用和有效的QKD方案，该方案具有有限键分析功能，该方案通过安装在佛罗伦萨（意大利）大都市区的21 dB损耗的光纤链路上执行。通过通过同一条光纤链路传输光同步信号，也可以证明量子通信与弱经典通信并存。