Phase estimation via quantum interferometry for noisy detectors

TL;DR

This paper presents a practical quantum interferometry method using phase-sensitive amplification after phase sensing, enabling high-precision measurements with imperfect detectors without prior loss characterization.

Contribution

It introduces an experimentally feasible technique employing amplification post-sensing to achieve optimal phase estimation despite detector losses.

Findings

Demonstrated phase estimation reaching optimal regime with coherent states.

Method is robust against detector imperfections and does not require loss calibration.

Applicable to high-sensitivity interferometry in practical settings.

Abstract

The sensitivity in optical interferometry is strongly affected by losses during the signal propagation or at the detection stage. The optimal quantum states of the probing signals in the presence of loss were recently found. However, in many cases of practical interest, their associated accuracy is worse than the one obtainable without employing quantum resources (e.g. entanglement and squeezing) but neglecting the detector's loss. Here we detail an experiment that can reach the latter even in the presence of imperfect detectors: it employs a phase-sensitive amplification of the signals after the phase sensing, before the detection. We experimentally demonstrated the feasibility of a phase estimation experiment able to reach its optimal working regime. Since our method uses coherent states as input signals, it is a practical technique that can be used for high-sensitivity interferometry and, in contrast to the optimal strategies, does not require one to have an exact characterization of the loss beforehand.