Gravitational wave detection with high frequency phonon trapping acoustic cavities

There are a number of theoretical predictions for astrophysical and cosmological objects, which emit high frequency (10(6) - 10(9) Hz) gravitation waves (GW) or contribute somehow to the stochastic high frequency GW background. Here we propose a new sensitive detector in this frequency band, which is based on existing cryogenic ultrahigh quality factor quartz bulk acoustic wave cavity technology, coupled to near-quantum-limited SQUID amplifiers at 20 mK. We show that spectral strain sensitivities reaching 10(-22) per root Hz per mode is possible, which in principle can cover the frequency range with multiple (>100) modes with quality factors varying between 10(6) and 10(10) allowing wide bandwidth detection. Due to its compactness and well-established manufacturing process, the system is easily scalable into arrays and distributed networks that can also impact the overall sensitivity and introduce coincidence analysis to ensure no false detections.