Satellite-to-Ground Continuous Variable Quantum Key Distribution: The Gaussian and Discrete Modulated Protocols in Low Earth Orbit

TL;DR

This paper compares Gaussian and discrete modulated continuous variable quantum key distribution protocols over satellite-to-ground links, demonstrating that Gaussian modulation with multidimensional reconciliation achieves better performance in low SNR conditions.

Contribution

It provides a comprehensive analysis of GM-CVQKD and DM-CVQKD protocols in satellite links, incorporating realistic atmospheric effects and advanced reconciliation methods.

Findings

GM-CVQKD outperforms DM-CVQKD in key rate and distance.

MD reconciliation enhances GM-CVQKD performance.

Positive secret key rates are achievable at larger distances with GM-CVQKD.

Abstract

The Gaussian modulated continuous variable quantum key distribution (GM-CVQKD) protocol is known to maximise the mutual information between two parties during quantum key distribution (QKD). An alternative modulation scheme is the discrete modulated CVQKD (DM-CVQKD) protocol. In this paper, we study the Phase Shift Keying (M-PSK) and Quadrature Amplitude Modulation (M QAM) DM-CVQKD protocols along with the GM-CVQKD protocol over a satellite-to-ground link in the low SNR regime. We use a satellite-to-ground link model which takes into account geometric losses, scintillation, and scattering losses from the link distance, atmospheric turbulence, and atmospheric aerosols, respectively. In addition, recent multidimensional (MD) and multilevel coding and multistage decoding (MLC-MSD) reconciliation method models in combination with multiedge-type low-density parity-check (MET-LDPC) code models have been used to determine the reconciliation efficiency. The results show that GM-CVQKD outperforms DM-CVQKD. In addition, GM-CVQKD with MD reconciliation outperforms GM-CVQKD with MLC-MSD reconciliation in the finite size limit by producing positive secret key rates at larger link distances and lower elevation angles.