Performance Analysis of Satellite-Based QKD Protocols

TL;DR

This study evaluates the performance of four satellite-based quantum key distribution protocols over LEO links, analyzing factors like QBER and secure key rate under various conditions.

Contribution

It provides a comparative analysis of four protocols' performance in satellite QKD, considering realistic atmospheric and operational factors.

Findings

Downlink links have lower QBER and higher key rates than uplinks.

BB84 outperforms B92 among prepare-and-measure protocols.

BBM92 achieves higher key rates than E91 in entanglement-based schemes.

Abstract

Satellite-based free-space quantum key distribution (QKD) provides a practical framework for achieving secure global communication beyond the limitations of optical fibers. In this work, the quantum bit error rate (QBER) and secure key rate of four representative protocols-BB84, B92, BBM92, and E91 are investigated over low earth orbit (LEO) links in both uplink and downlink configurations. The optical link is modeled using a Gaussian beam formalism, incorporating the effects of diffraction, pointing errors, atmospheric turbulence, and background noise contributions. The protocols are examined under day and night-time operating conditions, and their dependence on the zenith angle is analyzed. The findings show that downlink links generally exhibit lower QBER and higher secure key rates than uplinks, and among prepare-and-measure schemes, BB84 consistently outperforms B92, while in entanglement-based approaches, BBM92 achieves higher key rates than E91.