Sensitivity Bounds for Multiparameter Quantum Metrology

TLDR

Quantum multiparameter sensitivity can be enhanced by entanglement among particles, modes, or both, with particle‑separable states setting a shot‑noise limit that can be surpassed even without mode entanglement. The study determines precision limits for simultaneous estimation of multiple parameters in multimode interferometers, showing that adding mode entanglement can reach the Heisenberg limit. The authors provide optimal strategies that saturate these precision bounds.

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 that saturate the precision bounds are provided.