Stable Polarization Entanglement based Quantum Key Distribution over Metropolitan Fibre Network

TL;DR

This paper demonstrates a stable quantum key distribution system over metropolitan fiber networks using polarization-entangled photons, achieving continuous operation with low error rates and practical key rates.

Contribution

The work introduces a method for stable polarization-entangled QKD over deployed fibers with active polarization compensation, enabling real-world quantum communication.

Findings

Average QBER of 6.4% achieved

Final key rate of 109 bits per second

Stable operation over 10 km of deployed fiber

Abstract

We demonstrate a quantum key distribution implementation over deployed dark telecom fibers with polarisation-entangled photons generated at the O-band. One of the photons in the pairs are propagated through 10km of deployed fiber while the others are detected locally. Polarisation drifts experienced by the photons propagating through the fibers are compensated with liquid crystal variable retarders. This ensures continuous and stable QKD operation with an average QBER of 6.4% and a final key rate of 109 bits/s.