Passive polarization and phase stabilization scheme for Twin-Field QKD

TL;DR

This paper presents a passive stabilization scheme for Twin-Field QKD that maintains high interferometric visibility over extended periods, simplifying implementation in fiber-optic networks.

Contribution

It introduces a novel experimental setup combining a Sagnac-like interferometer with a Plug-and-Play configuration for passive phase and polarization stabilization in TF-QKD.

Findings

Achieved 95.3% interferometric visibility over 72 hours

Maintained low standard deviation of 0.47% in visibility

Setup adaptable to multi-user quantum networks

Abstract

Twin-Field Quantum Key Distribution requires first-order interference between coherent states sent by Alice and Bob in a mid-station Charlie. In order to obtain stable operation and maximum interferometric visibility, not only phase stabilization but also polarization control is required, especially in optical-fiber setups. In this paper, we propose an experimental setup that simultaneously provides passive stabilization of phase and polarization fluctuations by combining a Sagnac-like interferometer with a "Plug-and-Play" configuration employing Faraday mirrors. Experimental results show a net interferometric visibility maintained around 95.3% during 72 hours of continuous operation, with a standard deviation of 0.47%. The setup can be straightforwardly adapted to a multi-user scenario employing either a star network, a bus topology, or a combination of both.