Cavity-mediated coupling of mechanical oscillators limited by quantum backaction

TL;DR

This paper demonstrates phase-coherent coupling of two mechanical oscillators via an optical cavity, highlighting the effects of quantum backaction and its implications for quantum information transfer and entanglement.

Contribution

It reports the first realization of phase-coherent coupling between spatially separated mechanical oscillators mediated by an optical cavity, including the observation of quantum backaction effects.

Findings

Achieved phase-coherent coupling of mechanical oscillators

Observed noise and correlations due to optical coupling

Operated in the quantum backaction dominated regime

Abstract

A complex quantum system can be constructed by coupling simple quantum elements to one another. For example, trapped-ion or superconducting quantum bits may be coupled by Coulomb interactions, mediated by the exchange of virtual photons. Alternatively quantum objects can be coupled by the exchange of real photons, particularly when driven within resonators that amplify interactions with a single electro-magnetic mode. However, in such an open system, the capacity of a coupling channel to convey quantum information or generate entanglement may be compromised. Here, we realize phase-coherent interactions between two spatially separated, near-ground-state mechanical oscillators within a driven optical cavity. We observe also the noise imparted by the optical coupling, which results in correlated mechanical fluctuations of the two oscillators. Achieving the quantum backaction dominated regime opens the door to numerous applications of cavity optomechanics with a complex mechanical system. Our results thereby illustrate the potential, and also the challenge, of coupling quantum objects with light.