Power and temperature dependence of High Q superconducting resonators

An integrated temperature and power dependent model of a resonator internal quality factor predicts the loss contribution from two-level systems and quasiparticles simultaneously. At millikelvin temperatures, the sub-gap microwave photons generated by the resonator readout power drive the quasiparticle and phonon density far from its thermal equilibrium.
Here we propose a two-temperature, power, and temperature dependent model to evaluate resonator losses that define the driven quasiparticle density by a separate effective temperature than the bath temperature. The model also explores the contribution of the readout power for different power and temperature. The model is investigated on the resonators fabricated from epitaxial molecular beam epitaxy grown aluminum and titanium nitride on float-zone refined silicon. The resonators have quality factors above 1M. The contribution of various loss mechanisms is also examined.