Quantum-enhanced phase sensitivity in an all-fiber Mach-Zehnder interferometer

TL;DR

This paper demonstrates a fiber-based quantum interferometer that achieves a 10% quantum advantage in phase sensitivity, showcasing practical, alignment-free quantum sensing at telecom wavelengths.

Contribution

It introduces a fully fibered Mach-Zehnder interferometer converting polarization-entangled photons into energy-time entanglement for enhanced phase sensitivity.

Findings

Achieved 10% quantum advantage in phase sensitivity.

Operates at telecom wavelengths without post-selection.

Accounts for system imperfections in Fisher information analysis.

Abstract

Recent advances in quantum photonics have enabled increasingly robust protocols in optical phase estimation, achieving precisions beyond the standard quantum limit and approaching the Heisenberg limit. While intrinsic losses hinder the realization of unconditional super-sensitivity, reaching quantum advantage, defined as sensitivity surpassing that of any classical counterpart with identical resources, remains achievable. Here we experimentally demonstrate such an advantage using a fully fibered Mach-Zehnder-type interferometer operating at telecom wavelengths, free of post-selection. The scheme relies on the conversion of polarization-entangled photon pairs, a degree of freedom commonly favored for experimental convenience, into energy-time entanglement, which is particularly well suited for scalable fiber-based sensors. All system imperfections, including asymmetric losses and detector inefficiencies, are accounted for in the Fisher information analysis, yielding a measured quantum advantage of 10%. This result highlights the practicality of compact, alignment-free quantum interferometers for real-world sensing applications.