Strong backaction on a mechanical resonator by a few photons

Tanmoy bera, Vibhor Singh

Published 2023-09-13Version 1

Cavity electromechanical systems, consisting of a mechanical resonator coupled to an electromagnetic mode, are extensively used for sensing of various forces and controlling the vibrations of a mechanical mode down to their quantum limit. In the microwave domain, such devices based on magnetic-flux coupling have emerged as a promising platform with the potential to reach a single-photon strong coupling regime. Here, we demonstrate a flux-coupled electromechanical device using a frequency tunable superconducting transmon qubit, and a microwave cavity. By tuning the qubit in resonance with the cavity, the hybridized state (dressed mode) of the qubit and the cavity mode is used to achieve a magnetic field-dependent electromechanical coupling. It is established by performing an electromagnetically-induced transparency (EIT)-like experiment. At the largest applied field, we estimate the single-photon coupling rate of 60 kHz. Further, in the presence of the pump signal, we observe backaction, showing both cooling and heating of the mechanical mode. With a stronger pump, the dressed mode shows the signature of "super-splitting", and a strong backaction on the mechanical resonator, reflected in the broadening of the mechanical linewidth by a factor of 42 while using less than 1 photon in the dressed mode.