Probing of nonlinear hybrid optomechanical systems via partial accessibility

TL;DR

This paper investigates how to optimally probe atom-light-mechanics couplings in hybrid optomechanical systems using partial measurements, revealing that the light subsystem often provides the most information, especially with homodyne detection.

Contribution

It identifies the optimal subsystems for probing couplings in hybrid systems and analyzes the effectiveness of homodyne detection in extracting information.

Findings

Light is often the optimal subsystem for probing couplings.

Homodyne detection can extract significant information about the couplings.

The choice of subsystem depends on known or irrelevant couplings.

Abstract

Hybrid optomechanical systems are emerging as a fruitful architecture for quantum technologies. Hence, determining the relevant atom-light and light-mechanics couplings is an essential task in such systems. The fingerprint of these couplings is left in the global state of the system during non-equilibrium dynamics. However, in practice, performing measurements on the entire system is not feasible, and thus, one has to rely on partial access to one of the subsystems, namely the atom, the light, or the mechanics. Here, we perform a comprehensive analysis to determine the optimal subsystem for probing the couplings. We find that if the light-mechanics coupling is known or irrelevant, depending on the range of the qubit-light coupling, then the optimal subsystem can be either light or the qubit. In other scenarios, e.g., simultaneous estimation of the couplings, the light is usually the optimal subsystem. This can be explained as light is the mediator between the other two subsystems. Finally, we show that the widely used homodyne detection can extract a fair fraction of the information about the couplings from the light degrees of freedom.