Gaussian phase sensitivity of boson-sampling-inspired strategies

TL;DR

This paper analyzes the phase sensitivity of Gaussian-based interferometric schemes, revealing how measurement choices and imperfections influence precision, and introduces a new protocol surpassing previous non-classical state methods.

Contribution

It develops a Fisher information-based formalism for Gaussian interferometry, compares classical and non-classical states, and proposes a novel polychromatic protocol with enhanced sensitivity.

Findings

Coherent states and squeezing outperform non-classical states in phase estimation.

Homodyne detection is optimal for the proposed polychromatic protocol.

The formalism separates measurement, imperfections, and auxiliary system effects.

Abstract

In this work we study the phase sensitivity of generic linear interferometric schemes using Gaussian resources and measurements. Our formalism is based on the Fisher information. This allows us to separate the contributions of the measurement scheme, the experimental imperfections, and auxiliary systems. We demonstrate the strength of this formalism using a broad class of multimode Gaussian states that includes well-known results from single- and two-mode metrology scenarios. Using this, we prove that input coherent states or squeezing beat the non-classical states proposed in preceding boson-sampling-inspired phase-estimation schemes. We also develop a novel polychromatic interferometric protocol, demonstrating an enhanced sensitivity with respect to two-mode squeezed-vacuum states, for which the ideal homodyne detection is formally shown to be optimal.