Thermal Fluctuations in Cryogenic Quartz Resonators

Acoustic resonances at frequencies around 500 MHz and Q-factors exceeding one billion were reported in [1]. This was observed with the so-called BVA quartz resonators employing the non-contacting electrode technology [2]. Such resonators are the time-keeping elements of the most frequency-stable quartz oscillators [3]. By cooling the 400 MHz BVA resonator to 15 mK, which is well within the range of modern cryogen-free dilution systems (for example, http://www.bluefors.com), one can putatively observe the quantum behavior of macroscopic objects, as well as perform various high-precision tests of fundamental physics.