Loss Dependence on Geometry and Applied Power in Superconducting Coplanar Resonators

作者：Moe S. Khalil, F. C. Wellstood, Kevin D. Osborn · 发表于：IEEE Transactions on Applied Superconductivity · 年份：2010 · DOI：10.1109/tasc.2010.2090330 · 被引用次数：70 · 研究领域：Superconducting and THz Device Technology、Radio Frequency Integrated Circuit Design、Microwave Engineering and Waveguides

The loss in superconducting microwave resonators at low-photon numbers and low temperatures is not well understood but has implications for achievable coherence times in superconducting qubits. We have fabricated single-layer resonators with a high quality factor by patterning a superconducting aluminum film on a sapphire substrate. Four resonator geometries were studied with resonant frequencies ranging from 5 to 7 GHz: a quasi-lumped element resonator, a coplanar strip waveguide resonator, and two hybrid designs that contain both a coplanar strip and a quasi-lumped element. Transmitted power measurements were taken at 30 mK as a function of frequency and probe power. We find that the resonator loss, expressed as the inverse of the internal quality factor, decreases slowly over four decades of photon number in a manner not merely explained by loss from a conventional uniform spatial distribution of two-level systems in an oxide layer on the superconducting surfaces of the resonator.