Multimode circuit optomechanics near the quantum limit

TL;DR

This paper demonstrates tripartite optomechanical mixing in a hybrid system with a microwave cavity and two mechanical beams, achieving near-ground-state cooling and revealing a long-lived dark mode, advancing quantum entanglement prospects.

Contribution

It reports the first observation of tripartite optomechanical mixing and near-ground-state cooling in a three-degree-of-freedom hybrid system, a significant step forward in quantum optomechanics.

Findings

First evidence of tripartite optomechanical mixing.

Identification of a long-lived asymmetric dark mode.

Mechanical modes cooled close to the quantum ground state.

Abstract

The coupling of distinct systems underlies nearly all physical phenomena and their applications. A basic instance is that of interacting harmonic oscillators, which gives rise to, for example, the phonon eigenmodes in a crystal lattice. Particularly important are the interactions in hybrid quantum systems consisting of different kinds of degrees of freedom. These assemblies can combine the benefits of each in future quantum technologies. Here, we investigate a hybrid optomechanical system having three degrees of freedom, consisting of a microwave cavity and two micromechanical beams with closely spaced frequencies around 32 MHz and no direct interaction. We record the first evidence of tripartite optomechanical mixing, implying that the eigenmodes are combinations of one photonic and two phononic modes. We identify an asymmetric dark mode having a long lifetime. Simultaneously, we operate the nearly macroscopic mechanical modes close to the motional quantum ground state, down to 1.8 thermal quanta, achieved by back-action cooling. These results constitute an important advance towards engineering entangled motional states.