Sub-0.1 degree phase locking of a single-photon interferometer

TL;DR

This paper demonstrates a highly stable single-photon Mach-Zehnder interferometer with sub-0.1 degree phase locking over extended periods, enhancing precision in quantum communication and metrology.

Contribution

It introduces a novel phase locking technique using auxiliary light at a different wavelength, achieving continuous, low-crosstalk stabilization independent of signal fluctuations.

Findings

Phase stability of 0.05 degrees over 15 hours

Continuous phase locking with negligible crosstalk

Method applicable to various quantum interferometric setups

Abstract

We report a single-photon Mach-Zehnder interferometer stabilized to a phase precision of 0.05 degrees over 15 hours. To lock the phase, we employ an auxiliary reference light at a different wavelength than the quantum signal. The developed phase locking operates continuously, with negligible crosstalk, and for an arbitrary phase of the quantum signal. Moreover, its performance is independent of intensity fluctuations of the reference. Since the presented method can be used in a vast majority of quantum interferometric networks it can significantly improve phase-sensitive applications in quantum communication and quantum metrology.