Quantum metrology with a squeezed Kerr oscillator

TL;DR

This paper investigates the use of a Kerr nonlinear oscillator for quantum metrology, demonstrating high sensitivity states despite non-Gaussian effects and proposing a measurement protocol to optimize displacement sensing.

Contribution

It introduces a measurement-after-interaction protocol that enhances displacement sensitivity in Kerr nonlinear oscillators, accounting for realistic imperfections.

Findings

States have high quantum Fisher information for sensing displacements.

Simple quadrature measurements are insufficient for amplitude estimation.

Proposed protocol significantly improves sensitivity in realistic conditions.

Abstract

We study the squeezing dynamics in a Kerr-nonlinear oscillator, and quantify the metrological usefulness of the resulting states. Even if the nonlinearity limits the attainable squeezing by making the evolution non-Gaussian, the states obtained still have a high quantum Fisher information for sensing displacements. However, contrary to the Gaussian case, the amplitude of the displacement cannot be estimated by simple quadrature measurements. Therefore, we propose the use of a measurement-after-interaction protocol where a linear quadrature measurement is preceded by an additional nonlinear evolution, and show the significant sensitivity enhancement that can be obtained. Our results are robust when considering realistic imperfections such as energy relaxation, and can be implemented in state-of-the-art experimental setups.