Estimation theory of photon-magnon coupling strength in a driven-dissipative double-cavity-magnon system

TL;DR

This paper develops a quantum estimation framework for accurately determining photon-magnon coupling strength in a driven-dissipative double-cavity system, highlighting optimal measurement strategies and physical factors affecting precision.

Contribution

It introduces a quantum estimation approach for photon-magnon coupling in a complex system, identifying optimal measurements and analyzing physical influences on estimation accuracy.

Findings

Optimal Gaussian measurement nearly saturates quantum Fisher information bound.

Physical factors significantly influence estimation precision.

Identified the best subsystem for practical measurement.

Abstract

Cavity-magnon systems are emerging as a fruitful architecture for the integration of quantum technologies and spintronic technologies, where magnons are coupled to microwave photons via the magnetic-dipole interaction. Controllable the photon-magnon (P-M) couplings provide a powerful means of accessing and manipulating quantum states in such hybrid systems. Thus determining the relevant P-M couplings is a fundamental task. Here we address the quantum estimation problem for the P-M coupling strength in a double-cavity-magnon system with drive and dissipation. The effects of various physical factors on the estimation precision are investigated and the underlying physical mechanisms are discussed in detail. Considering that in practical experiments it is almost infeasible to perform measurements on the global quantum state of this composite system, we identify the optimal subsystem for performing measurements and estimations. Further, we evaluate the performance of different Gaussian measurements, indicating that optimal Gaussian measurement almost saturates the ultimate theoretical bound on the estimation precision given by the quantum Fisher information.