Designing open quantum systems for enabling quantum enhanced sensing through classical measurements

TL;DR

This paper demonstrates that quantum-enhanced sensing in open quantum systems can be achieved through simple classical measurements, simplifying practical implementation in experimental setups.

Contribution

It introduces a method to attain quantum enhancement via classical measurements in many-body open quantum systems, avoiding complex joint system-environment protocols.

Findings

Quantum enhancement achievable with photon counting and homodyne detection.

Application to open spin-boson models in trapped-ion or cavity QED.

Practical route for quantum metrology using classical measurement techniques.

Abstract

Quantum systems in nonequilibrium conditions, where coherent many-body interactions compete with dissipative effects, can feature rich phase diagrams and emergent critical behavior. Associated collective effects, together with the continuous observation of quanta dissipated into the environment -- typically photons -- allow to achieve quantum enhanced parameter estimation. However, protocols for tapping this enhancement typically involve intricate measurements on the combined system-environment state. Here we show that many-body quantum enhancement can in fact be obtained through classical measurements, such as photon counting and homodyne detection. We illustrate this in detail for a class of open spin-boson models which can be realized in trapped-ion or cavity QED setups. Our findings highlight a route towards the design of systems that enable a practical implementation of quantum enhanced metrology through continuous classical measurements.