Finite key performance of satellite quantum key distribution under practical constraints

TL;DR

This paper analyzes how practical engineering constraints impact the finite key performance of satellite quantum key distribution (SatQKD) systems, providing benchmarks for future mission design.

Contribution

It introduces a detailed analysis of practical limitations on SatQKD performance, including resource constraints and finite key effects, which was previously underexplored.

Findings

Practical constraints significantly limit key generation capacity.

Finite key effects are critical in realistic SatQKD scenarios.

Performance benchmarks guide future satellite QKD system design.

Abstract

Global-scale quantum communication networks will require efficient long-distance distribution of quantum signals. Optical fibre communication channels have range constraints due to exponential losses in the absence of quantum memories and repeaters. Satellites enable intercontinental quantum communication by exploiting more benign inverse square free-space attenuation and long sight lines. However, the design and engineering of satellite quantum key distribution (QKD) systems are difficult and characteristic differences to terrestrial QKD networks and operations pose additional challenges. The typical approach to modelling satellite QKD (SatQKD) has been to estimate performances with a fully optimised protocol parameter space and with few payload and platform resource limitations. Here, we analyse how practical constraints affect the performance of SatQKD for the Bennett-Brassard 1984 (BB84) weak coherent pulse decoy state protocol with finite key size effects. We consider engineering limitations and trade-offs in mission design including limited in-orbit tunability, quantum random number generation rates and storage, and source intensity uncertainty. We quantify practical SatQKD performance limits to determine the long-term key generation capacity and provide important performance benchmarks to support the design of upcoming missions.