# Utilization of the Superconducting Transition for Characterizing Low-Quality-Factor Superconducting Resonators

## TL;DR

This paper introduces a method to characterize low-quality-factor superconducting resonators by leveraging the superconducting transition of aluminum to isolate the resonance, enabling accurate measurement despite high dissipation.

## Contribution

It presents a novel experimental technique using the aluminum transition to measure the resonance of highly dissipative superconducting resonators.

## Key findings

- Resonance can be isolated by measuring above and below aluminum's superconducting transition.
- Quality factors of copper microstrips ranged from 10 to 67.
- Method is effective for different copper thicknesses from 50 nm to 150 nm.

## Abstract

Characterizing superconducting microwave resonators with highly dissipative elements is a technical challenge, but a requirement for implementing and understanding the operation of hybrid quantum devices involving dissipative elements, e.g. for thermal engineering and detection. We present experiments on $\lambda/4$ superconducting niobium coplanar waveguide (CPW) resonators, terminating at the antinode by a dissipative copper microstrip via aluminum leads, such that the resonator response is difficult to measure in a typical microwave environment. By measuring the transmission both above and below the superconducting transition of aluminum, we are able to isolate the resonance. We then experimentally verify this method with copper microstrips of increasing thicknesses, from 50 nm to 150 nm, and measure quality factors in the range of $10\sim67$ in a consistent way.