High Quality 3-Dimensional Aluminum Microwave Cavities

TL;DR

This study investigates aluminum superconducting 3D microwave cavities, demonstrating that surface treatments significantly enhance their internal quality factors, with the best cavity reaching 115 million at single photon levels.

Contribution

It introduces effective surface treatment methods that reproducibly produce high-Q aluminum cavities with internal quality factors exceeding 80 million.

Findings

Reproducible fabrication of high-Q cavities

Surface treatments improve quality factors significantly

Achieved a maximum quality factor of 115 million

Abstract

We present a comprehensive study of internal quality factors in superconducting stub-geometry 3-dimensional cavities made of aluminum. We use wet etching, annealing and electrochemichal polishing to improve the as machined quality factor. We find that the dominant loss channel is split between two-level system loss and an unknown source with 60:40 proportion. A total of 17 cavities of different purity, resonance frequency and size were studied. Our treatment results in reproducible cavities, with ten of them showing internal quality factors above 80 million at a power corresponding to an average of a single photon in the cavity. The best cavity has an internal quality factor of 115 million at single photon level.