High-dimensional quantum key distribution using a multi-plane light converter

TL;DR

This paper demonstrates high-dimensional quantum key distribution using a multi-plane light converter, achieving 5D and 25D QKD, and introduces a robust basis construction scalable to higher dimensions.

Contribution

The authors implement a large-scale MPLC as a high-dimensional mode sorter and propose a new basis construction robust to errors with scalable measurement complexity.

Findings

Demonstrated 5D QKD with six mutually unbiased bases.

Achieved 25D QKD with two mutually unbiased bases.

Proposed a basis construction scalable to higher dimensions.

Abstract

High-dimensional quantum key distribution (QKD) offers higher information capacity and stronger resilience to noise compared to its binary counterpart. However, these advantages are often hindered by the difficulty of realizing the required high-dimensional measurements and transformations. Here, we implement a large-scale multi-plane light converter (MPLC) and program it as a high-dimensional mode sorter of spatial modes for QKD. Using the MPLC, we demonstrate five-dimensional QKD with six mutually unbiased bases and 25-dimensional QKD with two mutually unbiased bases in the same experimental setup. Furthermore, we propose a construction of pairs of mutually unbiased bases that are robust to experimental errors, with measurement complexity scaling only with the square root of the encoded dimension. This approach paves the way for QKD implementations in higher dimensions.