Optimized phase sensing in a truncated SU(1,1) interferometer

TL;DR

This paper extends the analysis of a truncated SU(1,1) interferometer by including loss effects, optimizing homodyne detection for phase measurement, and experimentally demonstrating improved phase sensitivity and quantum limit beating.

Contribution

It introduces an optimized homodyne detection scheme accounting for loss and experimentally validates enhanced phase sensitivity in a truncated SU(1,1) interferometer.

Findings

Optimized homodyne detection reduces noise and enhances phase sensitivity.

Experimental results show beating the standard quantum limit.

Loss considerations are incorporated into the phase measurement optimization.

Abstract

Homodyne detection is often used for interferometers based on nonlinear optical gain media. For the configuration of a seeded, 'truncated SU(1,1)' interferometer Anderson et al. (Phys. Rev. A 95, 063843 (2017)) showed how to optimize the homodyne detection scheme and demonstrated theoretically that it can saturate the quantum Cramer-Rao bound for phase estimation. In this work we extend those results by taking into account loss in the truncated SU(1,1) interferometer and determining the optimized homodyne detection scheme for phase measurement. Further, we build a truncated SU(1,1) interferometer and experimentally demonstrate that this optimized scheme achieves a reduction in noise level, corresponding to an enhanced potential phase sensitivity, compared to a typical homodyne detection scheme for a two-mode squeezed state. In doing so, we also demonstrate an improvement in the degree to which we can beat the standard quantum limit with this device.