Nonlinear phase estimation enhanced by an actively correlated Mach-Zehnder interferometer

TL;DR

This paper proposes a nonlinear phase estimation scheme using a Mach-Zehnder interferometer with quantum states, achieving enhanced sensitivity beyond the standard quantum limit by active correlation readout.

Contribution

It introduces a novel scheme combining coherent and squeezed-vacuum states with active correlation detection to surpass classical phase sensitivity limits.

Findings

Phase sensitivity beats the standard quantum limit.

Approaches the quantum Cramér-Rao bound.

Discusses effects of photon loss on sensitivity.

Abstract

A nonlinear phase shift is introduced to a Mach-Zehnder interferometer (MZI), and we present a scheme for enhancing the phase sensitivity. In our scheme, one input port of a standard MZI is injected with a coherent state and the other input port is injected with one mode of a two-mode squeezed-vacuum state. The final interference output of the MZI is detected with the method of active correlation output readout. Based on the optimal splitting ratio of beam splitters, the phase sensitivity can beat the standard quantum limit and approach the quantum Cram\'{e}r-Rao bound. The effects of photon loss on phase sensitivity are discussed. Our scheme can also provide some estimates for units of $\chi^{(3)}$, due to the relation between the nonlinear phase shift and the susceptibility $\chi^{(3)}$ of the Kerr medium.