Round-Robin Differential Phase-Shift Quantum Key Distribution with Twisted Photons

TL;DR

This paper presents an experimental implementation of the round-robin differential phase-shift quantum key distribution protocol using twisted photons' orbital angular momentum, simplifying the setup and enhancing security in free-space quantum communication.

Contribution

It introduces a novel, simplified photonic implementation of the RRDPS protocol using orbital angular momentum, reducing complexity and improving practicality.

Findings

Successful experimental demonstration of RRDPS with twisted photons

Simplified setup with single phase elements for generation and detection

Potential for improved security in free-space quantum key distribution

Abstract

Quantum key distribution (QKD) offers the possibility for two individuals to communicate a securely encrypted message. From the time of its inception in 1984 by Bennett and Brassard, QKD has been the result of intense research. One technical challenge is the monitoring of signal disturbance in a QKD system to bound the information leakage towards an unwanted eavesdropper. Recently, the round-robin differential phase-shift (RRDPS) protocol, which encodes bits of information in a high-dimensional state space, was proposed to solve this exact problem. Since its introduction, many realizations of the RRDPS protocol were demonstrated using trains of coherent pulses. Here, we propose and experimentally demonstrate an implementation of the RRDPS protocol using the photonic orbital angular momentum degree of freedom. In particular, we show that Alice's generation stage and Bob's detection stage can each be reduced to a single phase element, greatly simplifying its implementation. Our scheme offers a practical demonstration of the RRDPS protocol which will suppress the need for monitoring signal disturbance in free-space channels.