Quantitative evaluation of defect-models in superconducting phase qubits

TL;DR

This paper combines high-precision spectroscopy and theoretical modeling to characterize the coupling between superconducting phase qubits and two-level defects, providing insights into defect origins and system parameters.

Contribution

It introduces a detailed experimental and theoretical approach to quantify qubit-defect interactions and compares multiple models for defect origins.

Findings

Strong qubit-defect coupling with minimal longitudinal component

Accurate determination of system parameters

Quantitative comparison of defect models

Abstract

We use high-precision spectroscopy and detailed theoretical modelling to determine the form of the coupling between a superconducting phase qubit and a two-level defect. Fitting the experimental data with our theoretical model allows us to determine all relevant system parameters. A strong qubit-defect coupling is observed, with a nearly vanishing longitudinal component. Using these estimates, we quantitatively compare several existing theoretical models for the microscopic origin of two-level defects.