Twin-field quantum key distribution (TFQKD) overcomes the linear rate-loss limit, which promises a boost of secure key rate over long distance. However, the complexity of eliminating the frequency differences between the independent laser sources hinders its practical application. We analyzed and determined the frequency stability requirements for implementing TFQKD using frequency-stabilized lasers. Based on this analysis, we proposed and demonstrated a simple and practical approach that utilizes the saturated absorption spectroscopy of acetylene as an absolute reference, eliminating the need for fast frequency locking to achieve TFQKD. Adopting the 4-intensity sending-or-not-sending TFQKD protocol, we experimentally demonstrated the TFQKD over 502, 301, and 201 km ultralow-loss optical fiber, respectively. We expect this high-performance scheme will find widespread usage in future intercity and free-space quantum communication networks.

中文翻译：

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具有本地频率参考的双场量子密钥分配


双场量子密钥分发 (TFQKD) 克服了线性速率损失限制，有望提高长距离安全密钥速率。然而，消除独立激光源之间的频率差异的复杂性阻碍了其实际应用。我们分析并确定了使用稳频激光器实施 TFQKD 的频率稳定性要求。基于此分析，我们提出并演示了一种简单实用的方法，该方法利用乙炔的饱和吸收光谱作为绝对参考，无需快速锁频即可实现 TFQKD。采用 4 强度发送或不发送 TFQKD 协议，我们分别在 502、301 和 201 km 超低损耗光纤上进行了 TFQKD 实验演示。我们预计这种高性能方案将在未来城际和自由空间量子通信网络中得到广泛应用。