Quantum key distribution (QKD) aims to generate secure private keys shared by two remote parties. With its security being protected by principles of quantum mechanics, some technology challenges remain towards practical application of QKD. The major one is the distance limit, which is caused by the fact that a quantum signal cannot be amplified while the channel loss is exponential with the distance for photon transmission in optical fiber. Here using the 3-intensity sending-or-not-sending protocol with the actively-odd-parity-pairing method, we demonstrate a fiber-based twin-field QKD over 1002 km. In our experiment, we developed a dual-band phase estimation and ultra-low noise superconducting nanowire single-photon detectors to suppress the system noise to around 0.02 Hz. The secure key rate is $9.53\times10^{-12}$ per pulse through 1002 km fiber in the asymptotic regime, and $8.75\times10^{-12}$ per pulse at 952 km considering the finite size effect. Our work constitutes a critical step towards the future large-scale quantum network.

中文翻译：

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超过 1000 公里光纤距离的实验性双场量子密钥分发

量子密钥分发 (QKD) 旨在生成由两个远程方共享的安全私钥。由于其安全性受到量子力学原理的保护，QKD 的实际应用仍然存在一些技术挑战。主要的一个是距离限制，这是由于量子信号无法放大而信道损耗与光子在光纤中传输的距离呈指数关系而引起的。在这里使用 3 强度发送或不发送协议和主动奇偶校验配对方法，我们展示了超过 1002 公里的基于光纤的双场 QKD。在我们的实验中，我们开发了双波段相位估计和超低噪声超导纳米线单光子探测器，以将系统噪声抑制到 0.02 Hz 左右。安全密钥费率为 9 美元。考虑到有限尺寸效应，在渐近状态下通过 1002 公里光纤每脉冲 53 \times10^{-12}$，在 952 公里处每脉冲 8.75\times10^{-12}$。我们的工作是迈向未来大规模量子网络的关键一步。