Self-healing high-dimensional quantum key distribution using hybrid spin-orbit Bessel states

TL;DR

This paper demonstrates a novel high-dimensional quantum key distribution method using hybrid spin-orbit Bessel states that can self-reconstruct and maintain security even with physical obstacles in free-space channels.

Contribution

It introduces a new approach to QKD with radial mode control using Bessel-Gaussian states, enabling secure transmission through obstacles with improved error rates.

Findings

Higher quantum state self-reconstruction with BG modes

QBER up to 3 times lower for BG modes

Secure transmission through partially obstructed links

Abstract

Using spatial modes for quantum key distribution (QKD) has become highly topical due to their infinite dimensionality, promising high information capacity per photon. However, spatial distortions reduce the feasible secret key rates and compromise the security of a quantum channel. In an extreme form such a distortion might be a physical obstacle, impeding line-of-sight for free-space channels. Here, by controlling the radial degree of freedom of a photon's spatial mode, we are able to demonstrate hybrid high-dimensional QKD through obstacles with self-reconstructing single photons. We construct high-dimensional mutually unbiased bases using spin-orbit hybrid states that are radially modulated with a non-diffracting Bessel-Gaussian (BG) profile, and show secure transmission through partially obstructed quantum links. Using a prepare-measure protocol we report higher quantum state self-reconstruction and information retention for the non-diffracting BG modes as compared to Laguerre-Gaussian modes, obtaining a quantum bit error rate (QBER) that is up to 3 times lower. This work highlights the importance of controlling the radial mode of single photons in quantum information processing and communication as well as the advantages of QKD with hybrid states.