Security analysis of quantum key distribution with small block length and its application to quantum space communications

TL;DR

This paper presents an improved finite-key security analysis for quantum key distribution that reduces data requirements, making satellite-based QKD more feasible and demonstrating its application to the Micius satellite.

Contribution

The authors develop a finite-key security analysis that decreases block length requirements by 14-17%, enhancing practical satellite QKD implementation.

Findings

Reduced block length requirement by 14-17%.

Application to Micius satellite shows positive secret key generation.

Potential to save weeks of measurement time in satellite QKD.

Abstract

The security of real-world quantum key distribution (QKD) critically depends on the number of data points the system can collect in a fixed time interval. To date, state-of-the-art finite-key security analyses require block lengths in the order of 1E4 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 systems, where the overall channel loss can go up to 70 dB or more. Here, we provide an improved finite-key security analysis which can reduce 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 $1E-5$ security level.