Twin-field (TF) quantum key distribution (QKD) can overcome fundamental secret-key-rate bounds on point-to-point QKD links, allowing us to reach longer distances than ever before. Since its introduction, several TFQKD variants have been proposed, and some of them have already been implemented experimentally. Most of them assume that the users can emit weak coherent pulses with a continuous random phase. In practice, this assumption is often not satisfied, which could open up security loopholes in their implementations. To close this loophole, we propose and prove the security of a TFQKD variant that relies exclusively on discrete phase randomization. Remarkably, our results show that it can also provide higher secret-key rates than an equivalent continuous-phase-randomized protocol.

中文翻译：

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具有完全离散相位随机化的双场量子密钥分配

双场（TF）量子密钥分发（QKD）可以克服点对点QKD链接上的基本密钥率限制，从而使我们能够比以前更长的距离。自从引入以来，已经提出了几种TFQKD变体，其中一些已经通过实验实现。他们中的大多数人假设用户可以发射具有连续随机相位的微弱相干脉冲。在实践中，通常无法满足该假设，这可能会在其实现中打开安全漏洞。为了解决这个漏洞，我们提出并证明了完全依赖离散相位随机化的TFQKD变体的安全性。值得注意的是，我们的结果表明，与等效的连续阶段随机协议相比，它还可以提供更高的密钥率。