Proof-of-principle experiment of reference-frame-independent quantum key distribution with phase coding

TL;DR

This paper demonstrates a proof-of-principle of reference-frame-independent quantum key distribution over 80 km, incorporating a new decoy state method and robust phase coding to counteract phase variations and polarization disturbances.

Contribution

It introduces a novel decoy state method for RFI-QKD with weak coherent sources and demonstrates robustness against phase and polarization disturbances.

Findings

Successful 80 km RFI-QKD experiment

Achieved secure key distribution over 50 km considering finite-key effects

Developed a robust system immune to phase and polarization disturbances

Abstract

We have demonstrated a proof-of-principle experiment of reference-frame-independent phase coding quantum key distribution (RFI-QKD) over an 80-km optical fiber. After considering the finite-key bound, we still achieve a distance of 50 km. In this scenario, the phases of the basis states are related by a slowly time-varying transformation. Furthermore, we developed and realized a new decoy state method for RFI-QKD systems with weak coherent sources to counteract the photon-number-splitting attack. With the help of a reference-frame-independent protocol and a Michelson interferometer with Faraday rotator mirrors, our system is rendered immune to the slow phase changes of the interferometer and the polarization disturbances of the channel, making the procedure very robust.