Finite key effects in satellite quantum key distribution

TL;DR

This paper analyzes finite key effects in satellite quantum key distribution, using empirical data to model system performance and guide future satellite QKD system design.

Contribution

It provides an empirically-derived model for finite key effects in SatQKD, informing system design and establishing performance benchmarks.

Findings

Finite key effects significantly impact secret key rates.

Link efficiency and background light are critical factors.

The model guides future satellite QKD mission planning.

Abstract

Global quantum communications will enable long-distance secure data transfer, networked distributed quantum information processing, and other entanglement-enabled technologies. Satellite quantum communication overcomes optical fibre range limitations, with the first realisations of satellite quantum key distribution (SatQKD) being rapidly developed. However, limited transmission times between satellite and ground station severely constrains the amount of secret key due to finite-block size effects. Here, we analyse these effects and the implications for system design and operation, utilising published results from the Micius satellite to construct an empirically-derived channel and system model for a trusted-node downlink employing efficient BB84 weak coherent pulse decoy states with optimised parameters. We quantify practical SatQKD performance limits and examine the effects of link efficiency, background light, source quality, and overpass geometries to estimate long-term key generation capacity. Our results may guide design and analysis of future missions, and establish performance benchmarks for both sources and detectors.