Planar Superconducting Resonators with Internal Quality Factors above One Million

TL;DR

This paper reports the fabrication of planar superconducting resonators with internal quality factors exceeding one million, achieved through precise interface control and a novel analysis method, advancing quantum computing components.

Contribution

The paper introduces a fabrication process that yields ultra-high quality factor superconducting resonators and a new analysis technique for accurate parameter extraction.

Findings

Internal quality factors above 10 million at high power

Low power quality factors approaching 2 million

Effective analysis method for resonator response

Abstract

We describe the fabrication and measurement of microwave coplanar waveguide resonators with internal quality factors above 10 million at high microwave powers and over 1 million at low powers, with the best low power results approaching 2 million, corresponding to ~1 photon in the resonator. These quality factors are achieved by controllably producing very smooth and clean interfaces between the resonators' aluminum metallization and the underlying single crystal sapphire substrate. Additionally, we describe a method for analyzing the resonator microwave response, with which we can directly determine the internal quality factor and frequency of a resonator embedded in an imperfect measurement circuit.