Useful Multiparticle Entanglement and Sub-Shot-Noise Sensitivity in Experimental Phase Estimation

TL;DR

This paper experimentally demonstrates how multiparticle entanglement can be used to surpass shot-noise limit in phase estimation, providing a general criterion and comparing different estimation protocols.

Contribution

It introduces a general criterion for identifying useful entangled states for enhanced phase estimation and experimentally demonstrates sub-shot-noise sensitivity using four-photon entangled states.

Findings

Achieved phase sensitivity beyond shot-noise limit with four-photon entangled states

Established a connection between multiparticle entanglement and sub-shot-noise uncertainty

Compared maximum likelihood and Bayesian phase estimation protocols

Abstract

We experimentally demonstrate a general criterion to identify entangled states useful for the estimation of an unknown phase shift with a sensitivity higher than the shot-noise limit. We show how to exploit this entanglement on the examples of a maximum likelihood as well as of a Bayesian phase estimation protocol. Using an entangled four-photon state we achieve a phase sensitivity clearly beyond the shot-noise limit. Our detailed comparison of methods and quantum states for entanglement enhanced metrology reveals the connection between multiparticle entanglement and sub-shot-noise uncertainty, both in a frequentist and in a Bayesian phase estimation setting.