A universal, plug-and-play synchronisation scheme for practical quantum networks

TL;DR

This paper introduces a universal, plug-and-play optical synchronization scheme for quantum networks, demonstrating high-visibility interference over 100 km, enabling practical long-distance quantum communication.

Contribution

It presents a novel, all-optical synchronization method using mature telecom technologies, compatible with various quantum network architectures, and free from jitter issues of previous solutions.

Findings

Achieved over 90% interference visibility at 100 km distance

Demonstrated compatibility with high network operation rates

Provided a simple, off-the-shelf component-based implementation

Abstract

We propose and experimentally demonstrate a plug-and-play, practical, and enabling method allowing to synchronize the building blocks of a quantum network in an all-optical way. Our scheme relies on mature and reliable classical telecommunication and non-linear optical technologies and can be implemented in a universal way with off-the-shelf components. Compared to already reported solutions, it allows achieving high-quality synchronization compatible with high network-operation rate and is free from opto-electronic jitters affecting servo-loop based configurations. We test our scheme with a genuine quantum optical method in terms of the interference between two photons coming from two remotely synchronized sources spaced by distances of up to 100 km. Measured visibilities well above 90% confirm the validity of our approach. Due its simplicity and high-quality performance, our scheme paves the way for the synchronization of long-distance quantum networks based on fibre, free-space, as well as hybrid solutions.