Large electromechanical coupling in inductively coupled electromechanics*

Light-matter interaction in optomechanical systems is the foundation for ultra-sensitive detection schemes measuring displacements, accelerations, and forces. In addition, this interaction enables the generation of mechanical quantum states and entangled states of photons and phonons. Electromechanical systems implement the field of optomechanics using microwave circuits. Most implementations realize the coupling using a mechanically compliant capacitance, demonstrating a maximum interaction rate of 280 Hz [1]. However, it was realized early on that inductive coupling schemes promise much higher interaction strengths even with the potential to reach the strong vacuum coupling regime.
Here, we demonstrate electromechanical coupling based on a partly suspended SQUID combined with a coplanar microwave resonator exceeding a coupling rate of 1 kHz. This coupling enables force sensitivities on a sub-attonewton level using an single-photon ultra-low power readout. We discuss the performance of the concept including the tunability of this coupling with magnetic field.
[1] Reed et al., Nature Physics 13, 1163 (2017)