Optimal Multiparameter Quantum Estimation of Magnonic Couplings in a Magnomechanical Cavity

TL;DR

This paper proposes a practical scheme for highly precise simultaneous estimation of magnonic couplings in a cavity system, demonstrating the advantages of heterodyne detection and quantum Fisher information analysis.

Contribution

It introduces an experimentally feasible method to enhance multiparameter quantum estimation in a magomechanical cavity, comparing estimation strategies and optimizing measurement techniques.

Findings

Simultaneous estimation outperforms individual strategies.

RLD-based QCRB provides lower bounds than SLD.

Heterodyne detection approaches the quantum limit under certain conditions.

Abstract

In this work, we introduce an experimentally viable scheme to enhance the simultaneous estimation precision of the couplings $G_{mc}$ and $G_{mb}$, with a particular focus on the performance of heterodyne detection. By comparing simultaneous and individual estimation strategies, we demonstrate that the simultaneous approach offers a notable advantage in our system. To support this, we compute the quantum Fisher information matrices (QFIMs) based on the symmetric logarithmic derivative (SLD) and the right logarithmic derivative (RLD). Our results show that the quantum Cram\'er Rao bound (QCRB) associated with the RLD is consistently lower than that of the SLD, indicating superior estimation precision. From a physical standpoint, this improvement reflects the system's enhanced capacity to encode, transfer, and extract quantum information while allowing optimal control of fundamental interactions. We show that increasing the Rabi frequency, cavity loss rate, and the average number of photons and phonons, combined with reduced mechanical damping and temperature, enhances the system's sensitivity to the coupling parameters. These mechanisms act on the available quantum resources, such as entanglement, squeezing, and state purity, leading to more precise estimations. Furthermore, our analysis reveals that under certain conditions, heterodyne detection can closely approach the ultimate precision set by the QFIM. This suggests that a measurement strategy based on heterodyne detection can offer an efficient and practical route for estimating the couplings $G_{mc}$ and $G_{mb}$, paving the way for high precision hybrid quantum sensors.