Power and temperature dependent model for high Q superconductor resonators

• Published in: APL quantum Vol. 2; no. 3
• Main Authors: Alexander, Ashish, Weddle, Christopher G., Richardson, Christopher J. K.
• Format: Journal Article
• Language: English
• Published: 01.09.2025
• ISSN: 2835-0103; 2835-0103
• DOI: 10.1063/5.0273506

Measuring the internal quality factor of coplanar waveguide superconducting resonators is an established method of determining small losses in superconducting devices. Often, resonator losses are attributed to two-level system (TLS) defects using a power dependent model for the quality factor. However, excess non-equilibrium quasiparticles can also limit the quality factor of superconducting resonators. Here, a two-temperature, power and temperature dependent model is used to evaluate resonator losses for titanium nitride and aluminum coplanar waveguide resonators with loss tangents of 10−5–10−6. This model enables a set of parameters to describe both the internal quality factor and fractional frequency shift of the resonator across a broad range of average cavity photon numbers, from 1 to 106, and temperatures between those limited by the experimental apparatus near 50 mK and thermal quasiparticle dominated. The presented model also offers potential insight into observing the temperature and power dependence of TLS–TLS interactions in these resonators.