Strong coupling in multimode quantum electromechanics

TL;DR

This paper demonstrates strong, tunable coupling between multiple mechanical modes in a superconducting microwave cavity system, enabling quantum entanglement and advancing multimode quantum electromechanics.

Contribution

It develops a multi-mode electromechanical system with strong coupling between mechanical modes mediated by a virtual photon in a superconducting cavity.

Findings

Strong coupling achieved between two mechanical modes.

Tunable inter-mechanical-mode coupling demonstrated.

Potential for generating mechanical entanglement.

Abstract

Cavity electro-(opto-)mechanics allows us to access not only single isolated but also multiple mechanical modes in a massive object. Here we develop a multi-mode electromechanical system in which a several membrane vibrational modes are coupled to a three-dimensional loop-gap superconducting microwave cavity. The tight confinement of the electric field across a mechanically-compliant narrow-gap capacitor brings the system into the quantum strong coupling regime under a red-sideband pump field. We demonstrate strong coupling between two mechanical modes, which is induced by two-tone parametric drives and mediated by a virtual photon in the cavity. The tunable inter-mechanical-mode coupling can be used to generate entanglement between the mechanical modes.