Use of a Local Local Oscillator for the Satellite-to-Earth Channel

TL;DR

This paper models the noise in a local local oscillator scheme for satellite-to-Earth continuous variable quantum key distribution, analyzing its impact on secure key rates considering atmospheric turbulence and practical satellite technology.

Contribution

It introduces a detailed noise model for LLO schemes in satellite-to-Earth CV-QKD, incorporating atmospheric turbulence effects and finite-size security analysis.

Findings

The noise model accurately predicts phase aberrations due to atmospheric turbulence.

Secure key rates are achievable with the proposed LLO scheme in satellite channels.

The model informs design considerations for quantum-enabled satellite systems.

Abstract

Continuous variable quantum key distribution (CV-QKD) offers information-theoretic secure key sharing between two parties. The sharing of a phase reference frame is an essential requirement for coherent detection in CV-QKD. Due to the potential attacks related to transmitting the local oscillator (LO) alongside quantum signals, there has been a focus on using local LOs (LLOs) to establish a shared phase reference. In this work, we develop a new noise model of a current state-of-the-art LLO scheme in the context of the satellite-to-Earth channel. In doing this, we encapsulate detailed phase-screen calculations that determine the coherent efficiency - a critical parameter in free-space CV-QKD that characterizes the wavefront aberrations caused by atmospheric turbulence. Using our new noise model we then determine the CV-QKD key rates for the satellite-to-Earth channel, secure under general attacks in the finite-size regime of the LLO scheme. Our results are of practical importance for next-generation quantum-enabled satellites that utilize multi-photon technology as opposed to single-photon technology.