In-field entanglement distribution over a 96 km-long submarine optical fibre

TL;DR

This paper demonstrates the successful distribution of entanglement over a 96 km submarine optical fibre, showing the potential for quantum communication using existing telecommunications infrastructure.

Contribution

It is the first to experimentally distribute entanglement over a long-distance submarine optical fibre, validating its use as a quantum channel.

Findings

257 photon pairs per second detected

Polarisation visibility above 90%

Feasibility of using submarine fibres for quantum communication

Abstract

Techniques for the distribution of quantum-secured cryptographic keys have reached a level of maturity allowing them to be implemented in all kinds of environments, away from any form of laboratory infrastructure. Here, we detail the distribution of entanglement between Malta and Sicily over a 96 km-long submarine telecommunications optical fibre cable. We used this standard telecommunications fibre as a quantum channel to distribute polarisation-entangled photons and were able to observe around 257 photon pairs per second, with a polarisation visibility above 90%. Our experiment demonstrates the feasibility of using deployed submarine telecommunications optical fibres as long-distance quantum channels for polarisation-entangled photons. This opens up a plethora of possibilities for future experiments and technological applications using existing infrastructure.