Strategy of satellite QKD with passive high brightness entangled photon pair source

TL;DR

This paper proposes a passive high-brightness entangled photon source for satellite QKD, providing an analytical model to optimize performance and reduce errors caused by multi-photon effects in high-brightness sources.

Contribution

It introduces a passive-intensity HBEPP source and an analytical model to optimize satellite QKD performance considering system losses and multi-photon effects.

Findings

Achieves 99.7% performance with fixed mean photon number

Provides an analytical model for measurement probabilities in asymmetric loss channels

Optimizes source brightness for satellite QKD systems

Abstract

A high-brightness entangled photon pair (HBEPP) source is essential for conducting entanglement-based quantum key distribution (QKD) between a satellite and a ground station. While an ultrabright source can overcome significant losses in satellite-based QKD (SQKD) and increase the sifted key rate, it also induces the multi-photon effect, raising the system's error rate. To accurately estimate system performance, we first present an analytical model for calculating the measurement probabilities of HBEPP distribution through an asymmetric loss channel. Based on this model, we propose the use of a passive-intensity HBEPP source for SQKD systems, assuming a polarization-independent channel and threshold detectors for measurement. We confirm that fixing the mean photon number at $\bar{\mu}=0.1$ achieves a performance of $99.7\%$ compared to the ideal one-way communication entanglement-based SQKD protocol, which is effectively optimizing the HBEPP source brightness in accordance with system losses.