Research Projects

High quality factor acoustic resonators operating in the microwave frequency are of prime interest for applications of quantum sensing, transduction, and memory operations. Achieving ultrahigh quality factor required for such quantum applications need a careful study of the various loss mechanisms (intrinsic and extrinsic) in the resonator. In this work, using a high overtone bulk acoustic resonator (HBAR), the intrinsic loss mechanisms will be studied through behaviour of the absorption of longitudinal acoustic waves through a three-phonon process and the two-level-system. The wide spectra of HBAR excited using a piezoelectric thin film permits excitation of coherent phonons modes from few GHz to 10’s of GHz. The wideband multimode behaviour of the mechanical system permits us to probe the loss mechanisms with reference to varying frequency of phonons and the temperature at which they are subjected to. Both piezoelectric and induced piezoelectric transduction schemes will be studied to identify the advantages and the shortcomings of each scheme for excitation of highly coherent phonon modes. A wide range of low loss single crystal substate as the acoustic cavity will be studied to arrive at the best combination of transducer and cavity for exciting long-lived high frequency phonons. The frequency of operation of the BAW resonators matches well with various planar qubits such as flux, phase, and transmon qubits operating in the microwave frequency. In this proposed work, the excitation and the read out of the phonons are through the piezoelectric/ferroelectric transducer and can be coupled to the superconducting circuits paving the way for on chip integration into a hybrid quantum system.