Simple and loss-tolerant free-space QKD using a squeezed laser

TL;DR

This paper proposes a simplified, loss-tolerant free-space CV QKD protocol using a squeezed laser and self-homodyne detection, which is highly robust and suitable for satellite communication.

Contribution

It introduces a new CV QKD protocol that is simpler, more robust, and loss-tolerant, eliminating the need for eavesdropper estimation under certain conditions.

Findings

Proper modulation at shot-noise level eliminates eavesdropper information leakage.

The protocol is highly tolerant to channel loss and turbulence-induced noise.

It is suitable for satellite-based quantum communication.

Abstract

We consider a continuous-variable (CV) quantum key distribution (QKD) protocol over free-space channels, which is simpler and more robust than typical CV QKD protocols. It uses a bright laser, squeezed and modulated in the amplitude quadrature, and self-homodyne detection. We consider a scenario, where the line of sight is classically monitored to detect active eavesdroppers, so that we can assume a passive eavesdropper. Under this assumption, we analyse security of the QKD protocol in the composable finite-size regime. Proper modulation of the squeezed laser to the shot-noise level can completely eliminate information leakage to the eavesdropper and also eliminate the turbulence-induced noise of the channel in the amplitude quadrature. Under these conditions, estimation of the eavesdropper's information is no longer required. The protocol is extremely robust to modulation noise and highly loss-tolerant, which makes it a promising candidate for satellite-based continuous-variable quantum communication.