Surface acoustic wave resonators in the quantum regime

We present systematic measurements of the quality factors of surface acoustic wave ( SAW) resonators on ST-X quartz in the gigahertz range at a temperature of 10 mK. We demonstrate an internal quality factor Q(i) approaching 0.5 million at 0.5 GHz and show that Q(i) >= 4.0 x 10(4) is achievable up to 4.4 GHz. We show evidence for a polynomial dependence of propagation loss on frequency, as well as a weak drive power dependence of Q(i) that saturates at low power, the latter being consistent with coupling to a bath of two-level systems. Our results indicate that SAW resonators are promising devices for integration with superconducting quantum circuits.