Low-loss electromechanical resonators with superconducting electrodes

Suppressing mechanical damping has been a major objective in the design of mechanical resonators. In mechanical quantum systems, high-Q resonances with long coherence time are critically required for achieving quantum state control and generating quantum entanglement. Micro- and nano-electromechanical systems typically utilize metal electrodes for actuation and detection, whose ohmic loss limits their Q-performance. Superconducting electrodes, with diminishing resistance below their transition temperatures, promise to reduce the electrode-induced losses. Here we develop electromechanical resonators with large-energy gap superconducting electrodes including NbN and Nb, targeting high Q resonances in the microwave and millimeter wave bands. These high-Q micromechanical entities could play a crucial role in advancing mechanical resonators within the quantum regime.