Polarisation drift compensation in an 8 km long Mach-Zehnder fibre-optical interferometer for quantum communication

TL;DR

This paper presents an experimental method to stabilize polarization drift and phase fluctuations in an 8 km fibre-optical Mach-Zehnder interferometer, enhancing quantum communication stability.

Contribution

The work introduces a combined polarization and phase stabilization technique using wavelength-multiplexed classical channels for long-term quantum communication.

Findings

Successful long-term stabilization of single-photon visibility.

Effective polarization control in a long-distance fibre interferometer.

Integration of classical channels for feedback control.

Abstract

We experimentally stabilise the polarisation drift between the arms of an 8 km-long fibre-optical Mach-Zehnder interferometer, while simultaneously compensating the phase fluctuations. The single photons are wavelength-multiplexed with three classical channels, which are used as feedback for the control systems. Two of these channels are used for the active polarisation control systems, while the other is used to phase-lock the interferometer. We demonstrate long-term stabilisation of the single-photon visibility when polarisation control is used.