Improving the Quality Factor of Microwave Compact Resonators by Optimizing their Geometrical Parameters

TL;DR

This study systematically investigates how geometrical parameters of Nb superconducting microwave resonators affect their quality factors, achieving significant improvements by optimizing design features relevant for quantum technologies.

Contribution

It demonstrates that increasing capacitor finger distance, width, and impedance enhances the quality factor, confirming the surface loss hypothesis and providing design guidelines.

Findings

Quality factors increased from 210,000 to 500,000.

Quality factors positively correlated with capacitor finger distance and width.

Results support surface-dominated loss hypothesis.

Abstract

Applications in quantum information processing and photon detectors are stimulating a race to produce the highest possible quality factor on-chip superconducting microwave resonators. We have tested the surface-dominated loss hypothesis by systematically studying the role of geometrical parameters on the internal quality factors of compact resonators patterned in Nb on sapphire. Their single-photon internal quality factors were found to increase with the distance between capacitor fingers, the width of the capacitor fingers, and the impedance of the resonator. Quality factors were improved from 210,000 to 500,000 at T = 200 mK. All of these results are consistent with our starting hypothesis.