Sensitivity of quantum-enhanced interferometers

TL;DR

This paper analyzes different configurations of quantum-enhanced interferometers, demonstrating that their sensitivity limits are governed by the same fundamental equations regardless of their linear or non-linear nature.

Contribution

It provides a unified framework using the Quantum Cramer-Rao bound to compare the sensitivity limits of various quantum interferometer schemes.

Findings

Sensitivity limits are consistent across different interferometer types.

Unified equations describe the practical sensitivity bounds.

Results build on and extend Caves' foundational work.

Abstract

We consider various configuration of quantum-enhanced interferometers, both linear (SU(2)) and non-linear (SU(1,1)) ones, as well as hybrid SU(2)/SU(1,1) schemes. Using the unified modular approach, based on the Quantum Cramer-Rao bound, we show that in all practical cases, their sensitivity is limited by the same equations (95) or (97) which first appeared in the pioneering work by C.Caves [Phys.Rev.D 23, 1693 (1981)].