Quantum metrology with a non-linear kicked Mach-Zehnder interferometer

TL;DR

This paper investigates a non-linear kicked Mach-Zehnder interferometer's sensitivity, revealing conditions under which it can achieve Heisenberg-limited scaling and how non-linear kicks enhance sensitivity under damping.

Contribution

It introduces a non-linear kicked version of the Mach-Zehnder interferometer and analyzes its sensitivity, highlighting the role of squeezing and non-linear kicks in quantum metrology.

Findings

Heisenberg-limited scaling occurs with dominant squeezing and no damping.

Non-linear kicks can significantly boost sensitivity at moderate damping.

Sensitivity depends on phase shift, kicking strength, photon number, and damping.

Abstract

We study the sensitivity of a Mach-Zehnder interferometer that contains in addition to the phase shifter a non-linear element. By including both elements in a cavity or a loop that the light transverses many times, a non-linear kicked version of the interferometer arises. We study its sensitivity as function of the phase shift, the kicking strength, the maximally reached average number of photons, and damping due to photon loss for an initial coherent state. We find that for vanishing damping Heisenberg-limited scaling of the sensitivity arises if squeezing dominates the total photon number. For small to moderate damping rates the non-linear kicks can considerably increase the sensitivity as measured by the quantum Fisher information per unit time.