Sensitivity Bounds for Multiparameter Quantum Metrology

TL;DR

This paper establishes fundamental precision bounds for estimating multiple parameters simultaneously in quantum interferometry, highlighting how entanglement enhances measurement sensitivity beyond classical limits.

Contribution

It derives the ultimate precision bounds for multiparameter quantum metrology and identifies optimal strategies to reach these bounds using entanglement.

Findings

Particle-separable states define the shot-noise limit.

Mode entanglement enables surpassing the shot-noise limit.

Adding mode entanglement can reach the Heisenberg limit.

Abstract

We identify precision limits for the simultaneous estimation of multiple parameters in multimode interferometers. Quantum strategies to enhance the multiparameter sensitivity are based on entanglement among particles, modes or combining both. The maximum attainable sensitivity of particle-separable states defines the multiparameter shot-noise limit, which can be surpassed without mode entanglement. Further enhancements up to the multiparameter Heisenberg limit are possible by adding mode entanglement. Optimal strategies which saturate the precision bounds are provided.