Enhanced phase sensitivity in a Mach-Zehnder interferometer via photon recycling

TL;DR

This paper introduces a photon recycling scheme in a Mach-Zehnder interferometer that significantly enhances phase sensitivity beyond traditional methods, even with photon loss, by leveraging quantum Cramer-Rao bounds and underlying mechanisms.

Contribution

The paper presents a novel photon recycling approach in a Mach-Zehnder interferometer that surpasses traditional phase sensitivity limits using coherent states and homodyne detection.

Findings

Achieves an enhancement factor of 9.32 in phase sensitivity

Lower quantum Cramer-Rao bound than traditional schemes

QCRB depends on phase shift, unlike traditional schemes

Abstract

We propose an alternative scheme for phase estimation in a Mach-Zehnder interferometer (MZI) with photon recycling. It is demonstrated that with the same coherent-state input and homodyne detection, our proposal possesses a phase sensitivity beyond the traditional MZI. For instance, it can achieve an enhancement factor of 9.32 in the phase sensitivity compared with the conventional scheme even with a photon loss of 10% on the photon-recycled arm. From another point of view, the quantum Cramer-Rao bound (QCRB) is also investigated. It is found that our scheme is able to achieve a lower QCRB than the traditional one. Intriguingly, the QCRB of our scheme is dependent of the phase shift phi while the traditional scheme has a constant QCRB regardless of the phase shift. Finally, we present the underlying mechanisms behind the enhanced phase sensitivity. We believe that our results provide another angle from which to enhance the phase sensitivity in a MZI via photon recycling.