Towards cavity quantum circuit electromechanics with millimiter-sized silicon nitride membranes

Due to their extremely high mechanical quality factors, silicon nitride membranes are commonplace in optomechanical experiments conducted with light fields. However, to strongly couple optical radiation to the vibratory motion of such membranes down in the quantum regime is still a sought-after target in these experiments.
We use here an original assembly to couple instead microwave radiation to a vibrating membrane of submillimiter dimensions, obtaining interaction strengths approaching state of the art values achieved in the optical realm.
The assembly is based on a mechanically adjustable pressing frame through spring screws, that holds a chip with an integrated lumped element resonator antenna facing another chip hosting the membrane. The membrane is coated with a layer of metal so that the two chips couple capacitively to form a resonant circuit, the capacitance of which, and thus its resonance frequency, is modulated by the membrane vibrations.
Besides its potential to challenge the foundations of quantum mechanics at unconventional mass and length scales, our electromechanical device may be well suited to study nonlinear phenomena in the framework of classical mechanics such as the emergence of chaotic dynamics in the weak damping limit.