Phase matching condition for enhancement of phase sensitivity in quantum metrology

TL;DR

This paper derives a phase matching condition that maximizes phase sensitivity in a Mach-Zehnder interferometer, applicable to various input states and robust against photon losses, enhancing quantum metrology precision.

Contribution

It introduces a universal phase matching condition for optimizing phase sensitivity in quantum interferometry with arbitrary input states.

Findings

Maximal Fisher information at the phase matching condition.

Enhanced phase sensitivity under the condition.

Robustness of the condition with photon losses.

Abstract

We find a phase matching condition for enhancement of sensitivity in a Mach-Zehnder interferometer illuminated by an arbitrary state in one input port and an odd(even) state in the other port. Under this condition, the Fisher information becomes maximal with respect to the relative phase of two modes and the phase sensitivity is enhanced. For the case with photon losses, we further find that the phase matching condition keeps unchanged with a coherent state and a coherent superposition state as the input states.