Quantum key distribution (QKD) offers a reliable solution to communication problems that require long-term data security. For its widespread use, however, the rate and reach of QKD systems must be improved. Twin-field (TF) QKD is a step forward toward this direction, with early demonstrations suggesting it can beat the current rate-versus-distance records. A recently introduced variant of TF-QKD is particularly suited for experimental implementation, and has been shown to offer a higher key rate than other variants in the asymptotic regime, where users exchange an infinite number of signals. Here, we extend the security of this protocol to the finite-key regime, showing that it can overcome the fundamental bounds on point-to-point QKD with ~10¹⁰ transmitted signals. In many practical regimes of interest, our analysis offers higher key rates than those of alternative variants. Moreover, some of the techniques we develop are applicable to the finite-key analysis of other QKD protocols.

量子密钥分发（QKD）为需要长期数据安全的通信问题提供了可靠的解决方案。然而，对于其广泛使用，必须提高QKD系统的速度和范围。双场（TF）QKD是朝着这个方向迈出的一步，早期的演示表明它可以击败当前的速度与距离记录。最近推出的TF-QKD变体特别适合于实验实现，并且已显示出比渐进体制中的其他变体（用户交换无限数量的信号）提供更高的密钥速率。在这里，我们将该协议的安全性扩展到有限键机制，这表明它可以克服点对点QKD的基本限制，大约需要10 ¹⁰传输信号。在许多实际感兴趣的机制中，我们的分析提供的密钥率高于其他变体。此外，我们开发的某些技术适用于其他QKD协议的有限键分析。