The security of quantum key distribution (QKD) is severely threatened by discrepancies between realistic devices and theoretical assumptions. Recently, a significant framework called the reference technique was proposed to provide security against arbitrary source flaws under current technology such as state preparation flaws, side channels caused by mode dependencies, the Trojan horse atttacks and pulse correlations. Here, we adopt the reference technique to prove security of an efficient four-phase measurement-device-independent QKD using laser pulses against potential source imperfections. We present a characterization of source flaws and connect them to experiments, together with a finite-key analysis against coherent attacks. In addition, we demonstrate the feasibility of our protocol through a proof-of-principle experimental implementation and achieve a secure key rate of 253 bps with a 20 dB channel loss. Compared with previous QKD protocols with imperfect devices, our study considerably improves both the secure key rate and the transmission distance, and shows application potential in the practical deployment of secure QKD with device imperfections.

翻译：量子密钥分发（QKD）的安全性受到实际器件与理论假设之间存在差异的严重威胁。最近，一种名为参考技术的重要框架被提出，可在当前技术条件下（如态制备缺陷、由模式依赖性导致的侧信道、特洛伊木马攻击以及脉冲关联等）针对任意光源缺陷提供安全性保障。本文采用参考技术，证明了使用激光脉冲的高效四相测量设备无关QKD在应对潜在光源不完美时的安全性。我们给出了光源缺陷的表征方法，并将其与实验相关联，同时针对相干攻击进行了有限密钥分析。此外，我们通过原理验证实验证明了所提协议的可行性，并在20 dB信道损耗下实现了253 bps的安全密钥速率。与先前采用不完美器件的QKD协议相比，我们的研究在安全密钥速率和传输距离两方面均有显著提升，展示了在器件不完美条件下安全QKD实际部署中的应用潜力。