All-optical turbulence mitigation for free-space quantum key distribution using stimulated parametric down-conversion

TL;DR

This paper introduces an all-optical method using stimulated parametric down-conversion to dynamically correct atmospheric turbulence effects in free-space quantum key distribution, significantly improving security and reliability.

Contribution

It presents a novel turbulence mitigation scheme based on phase conjugation, with theoretical modeling and experimental validation for robust quantum communication.

Findings

Reduces quantum error rates below security thresholds under strong turbulence

Demonstrates improved secure key rates in high-dimensional QKD

Provides guidelines for optimal basis and spatial property selection

Abstract

In this work, we propose and demonstrate a turbulence-resilient scheme for free-space quantum communication. By leveraging the phase conjugation property of stimulated parametric down-conversion, our scheme enables all-optical dynamic correction of spatial-mode distortion induced by atmospheric turbulence, thereby enhancing the secure key rate in high-dimensional quantum key distribution. We develop a theoretical model that provides detailed guidelines for selecting the optimal basis and spatial properties needed to maximize the efficiency of the proposed scheme. Both numerical simulations and experimental results show that, even under strong turbulence, our scheme can reduce the quantum error rates well below the security threshold. These results highlight the potential of nonlinear optical approaches as powerful tools for robust quantum communication in realistic free-space environments. Our work could have important implications for the practical implementation of secure quantum channels over long free-space distances.