Metropolitan-scale Entanglement Distribution with Co-existing Quantum and Classical Signals in a single fiber

TL;DR

This paper demonstrates the successful distribution of high-fidelity polarization-entangled quantum signals alongside classical signals in a single fiber over 100 km, addressing key challenges for metropolitan-scale quantum networks.

Contribution

It introduces a method for co-propagating quantum and classical signals in the same fiber, enabling polarization entanglement distribution at metropolitan distances.

Findings

High-fidelity entanglement distribution over 100 km fiber

Successful co-propagation of quantum and classical signals

Feasibility of integrated quantum-classical metropolitan networks

Abstract

The development of prototype metropolitan-scale quantum networks is underway and entails transmitting quantum information via single photons through deployed optical fibers spanning several tens of kilometers. The major challenges in building metropolitan-scale quantum networks are compensation of polarization mode dispersion, high-precision clock synchronization, and compensation for cumulative transmission time fluctuations. One approach addressing these challenges is to co-propagate classical probe signals in the same fiber as the quantum signal. Thus, both signals experience the same conditions, and the changes of the fiber can therefore be monitored and compensated. Here, we demonstrate the distribution of polarization entangled quantum signals co-propagating with the White Rabbit Precision Time Protocol (WR-PTP) classical signals in the same single-core fiber strand at metropolitan-scale distances. Our results demonstrate the feasibility of this quantum-classical coexistence by achieving high-fidelity entanglement distribution between nodes separated by 100 km of optical fiber. This advancement is a significant step towards the practical implementation of robust and efficient metropolitan-scale quantum networks.