The security of real-world quantum key distribution (QKD) critically depends on the number of data points the system can collect in a finite time interval. To date, state-of-the-art finite-key security analyses require block lengths in the order of ${10}^4\mathrm{bits}$ to obtain positive secret keys. This requirement, however, can be very difficult to achieve in practice, especially in the case of entanglement-based satellite QKD, where the overall channel loss can go up to 70 dB or more. Here, we provide an improved finite-key security analysis which reduces the block length requirement by 14% to 17% for standard channel and protocol settings. In practical terms, this reduction could save entanglement-based satellite QKD weeks of measurement time and resources, thereby bringing space-based QKD technology closer to reality. As an application, we use the improved analysis to show that the recently reported Micius QKD satellite is capable of generating positive secret keys with a ${10}^{-5}$ security level.

中文翻译：

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小块长度的量子密钥分配的安全性分析及其在量子空间通信中的应用

现实世界中的量子密钥分发（QKD）的安全性严重取决于系统可以在有限的时间间隔内收集的数据点的数量。迄今为止，最新的有限键安全性分析要求的块长度为${10}^4位$获得肯定的秘密密钥。但是，实际上很难达到这一要求，尤其是在基于纠缠的卫星QKD的情况下，其中总信道损耗可能高达70 dB或更高。在这里，我们提供了一种改进的有限键安全性分析，对于标准通道和协议设置，该分析将块长度要求降低了14％到17％。实际上，这种减少可以节省基于纠缠的卫星QKD几周的测量时间和资源，从而使基于空间的QKD技术更接近现实。作为一个应用程序，我们使用改进的分析结果表明，最近报道的Micius QKD卫星能够生成具有以下特征的正密钥：${10}^{-5}$ 安全级别。