Dielectric loss extraction for superconducting microwave resonators

TL;DR

This paper presents a new circuit-model-based method for accurately extracting dielectric TLS loss in superconducting resonators, enabling precise measurement of very low-loss materials relevant for quantum circuits.

Contribution

The authors introduce a novel TLS loss extraction technique using circuit modeling and multiple resonator designs, improving accuracy for materials with extremely low loss.

Findings

Successfully extracted TLS loss of 1.02 x 10^-3 for sputtered Al2O3.

Demonstrated the method's ability to measure materials with TLS loss below 10^-6.

Observed an 11% difference in loss measurement with and without the new method.

Abstract

The investigation of two-level-state (TLS) loss in dielectric materials and interfaces remains at the forefront of materials research in superconducting quantum circuits. We demonstrate a method of TLS loss extraction of a thin film dielectric by measuring a lumped element resonator fabricated from a superconductor-dielectric-superconductor trilayer. We extract the dielectric loss by formulating a circuit model for a lumped element resonator with TLS loss and then fitting to this model using measurements from a set of three resonator designs: a coplanar waveguide resonator, a lumped element resonator with an interdigitated capacitor, and a lumped element resonator with a parallel plate capacitor that includes the dielectric thin film of interest. Unlike other methods, this allows accurate measurement of materials with TLS loss lower than $10^{-6}$. We demonstrate this method by extracting a TLS loss of $1.02 \times 10^{-3}$ for sputtered $\mathrm{Al_2O_3}$ using a set of samples fabricated from an $\mathrm{Al/Al_2O_3/Al}$ trilayer. We observe a difference of 11$\%$ between extracted loss of the trilayer with and without the implementation of this method.