Digital synchronization for continuous-variable quantum key distribution

TL;DR

This paper introduces a digital synchronization method for continuous-variable quantum key distribution systems, enabling cost-effective and adaptable secure communication over optical fibers without hardware changes.

Contribution

It proposes a modulation format independent digital synchronization procedure for CV-QKD systems with experimental validation over fiber links.

Findings

Effective synchronization over 10-20 km fiber spans

No hardware modifications needed for implementation

Compatible with various modulation formats

Abstract

Continuous variable quantum key distribution (CV-QKD) is a promising emerging technology for the distribution of secure keys for symmetric encryption. It can be readily implemented using commercial off-the-shelf optical telecommunications components. A key requirement of the CV-QKD receiver is the ability to measure the quantum states at the correct time instance and rate using the correct orthogonal observables, referred to as synchronization. We propose a digital synchronization procedure for a modern CV-QKD system with locally generated local oscillator for coherent reception. Our proposed method is modulation format independent allowing it to be used in a variety of CV-QKD systems. We experimentally investigate its performance with a Gaussian modulated CV-QKD system operating over a 10-20 km span of standard single mode fibre. Since the procedure does not require hardware modifications it paves the way for cost-effective QKD solutions that can adapt rapidly to changing environmental conditions.