Analysis of untrusted-node quantum key distribution from a geostationary satellite

TL;DR

This paper evaluates the performance of twin-field and mode-pairing quantum key distribution protocols via satellite, demonstrating feasible secret key rates with moderate ground telescope sizes for global quantum communication.

Contribution

It provides a detailed simulation-based analysis of untrusted-node QKD using geostationary satellites, highlighting the protocols' high resilience to loss and scalability potential.

Findings

Secret key rates of a few hundred bits/sec are achievable with realistic detectors.

Feasibility of secret key generation with ground telescopes as small as 20 cm.

High scalability potential for satellite-based untrusted-node QKD.

Abstract

In pursuit of a global quantum key distribution (QKD) network, a service based on untrusted nodes on geostationary satellites could offer wide coverage, continuous operation, and enhanced security compared to the trusted node alternative. Although this scenario has been studied for entanglement-based protocols, such an approach would require large-area telescopes both on the ground and in space. In this work, we analyze the performance of two QKD protocols well adapted to this scenario, namely twin-field (TF) and mode-pairing (MP) QKD, which exhibit high resilience to high-loss channels. Leveraging an in-depth simulation of communication channels corrected with adaptive optics, we assess the expected secret key rates for both protocols in a configuration involving two 50 cm telescopes on board the satellite and ground-based telescopes ranging from 20 cm to 1 m in aperture. Our results show that, in the best case and considering realistic detectors, it is possible to achieve secret key rates on the order of a few hundred bit/s for both TF and MP-QKD. We show, notably, that secret key generation is potentially feasible even with 20 cm ground telescopes, highlighting the high scalability potential of such a configuration.