Characterization and stability measurement of deployed multicore fibers for quantum applications

TL;DR

This paper characterizes the phase stability of 25 km underground multicore fibers for quantum communication, demonstrating their potential for long-distance quantum applications beyond laboratory conditions.

Contribution

First to analyze phase stability of long-distance underground multicore fibers for quantum communication, showing their suitability for real-world quantum applications.

Findings

Multicore fibers exhibit stable phase properties over 25 km underground.

Underground installation maintains fiber stability suitable for quantum protocols.

Potential for implementing high-dimensional quantum key distribution over long distances.

Abstract

Multicore fibers are expected to be a game-changer in the coming decades thanks to their intrinsic properties, allowing a larger transmission bandwidth and a lower footprint in optical communications. In addition, multicore fibers have recently been explored for quantum communication, attesting their uniqueness in transporting high-dimensional quantum states. However, investigations and experiments reported in literature have been carried out in research laboratories, typically making use of short fiber links in controlled environments. Thus, the possibility of using long distance multicore fibers for quantum applications is still to be proven. We here characterize for the first time, in terms of phase stability, multiple strands of a 4-core multicore fiber installed underground in the city of L'Aquila, with an overall fiber length up to about 25 km. In this preliminary study, we investigate the possibility of using such an infrastructure to implement quantum-enhanced schemes, such as high-dimensional quantum key distribution, quantum-based environmental sensors, and more in general quantum communication protocols.