Material Loss Model Calibration for Tantalum Superconducting Resonators

TL;DR

This paper presents a new analytical framework for calibrating material loss in tantalum superconducting resonators, enabling better understanding of loss mechanisms across frequencies and temperatures for quantum circuit applications.

Contribution

It introduces a simple, analytical model for TLS loss calibration applicable to superconducting resonators, with empirical insights into frequency-dependent loss behaviors in tantalum.

Findings

The model accurately characterizes TLS loss without numerical simulations.

Frequency-dependent trends suggest additional loss mechanisms beyond standard models.

The methodology applies broadly to superconducting materials and resonator designs.

Abstract

Material research is a key frontier in advancing superconducting qubit and circuit performance. In this work, we develop a simple and broadly applicable framework for accurately characterizing two-level system (TLS) loss using internal quality factor measurements of superconducting transmission line resonators over a range of temperatures and readout powers. We applied this method to a series of $\alpha$-Ta resonators that span a wide frequency range, thus providing a methodology for probing the loss mechanisms in the fabrication process of this emerging material for superconducting quantum circuits. We introduce an analytical model that captures the loss behavior without relying on numerical simulations, enabling straightforward interpretation and calibration. Additionally, our measurements reveal empirical frequency-dependent trends in key parameters of the model, suggesting contributions from mechanisms beyond the standard tunneling model of TLSs.