Phonon Quantum Nondemolition Measurements in Nonlinearly Coupled Optomechanical Cavities

TL;DR

This paper explores quantum nondemolition measurements of phonon number in optomechanical cavities with quadratic coupling, enabling the study of quantum states of mechanical resonators and testing decoherence theories.

Contribution

It establishes a relaxed condition on linear coupling for QND phonon measurements in systems with quadratic optomechanical coupling.

Findings

Relaxed limits on linear coupling enable QND measurements.

QND measurements can probe decoherence of mechanical Fock states.

Provides a platform for testing quantum collapse theories.

Abstract

In the field of cavity optomechanics, proposals for quantum nondemolition (QND) measurements of phonon number provide a promising avenue by which one can study the quantum nature of nanoscale mechanical resonators. Here, we investigate these QND measurements for an optomechanical system whereby quadratic coupling arises due to shared symmetries between a single optical resonance and a mechanical mode. We establish a relaxed limit on the amount of linear coupling that can exist in this type of system while still allowing for a QND measurement of Fock states. This new condition enables optomechanical QND measurements, which can be used to probe the decoherence of mesoscopic mechanical Fock states, providing an experimental testbed for quantum collapse theories.