Microresonators fabricated from high-kinetic-inductance Aluminum films

TL;DR

This study demonstrates that disordered Aluminum films can be used to create high-impedance, ultra-short superconducting resonators with quality factors comparable to conventional materials, suitable for advanced microwave applications.

Contribution

It introduces high-kinetic-inductance Aluminum films for fabricating ultra-short, high-impedance superconducting resonators with well-characterized losses.

Findings

Resonators achieve quality factors comparable to conventional superconductors.

High kinetic inductance enables ultra-short, high-impedance resonators.

Losses are primarily due to coupling with two-level systems.

Abstract

We have studied superconducting coplanar-waveguide (CPW) resonators fabricated from disordered (granular) films of Aluminum. Very high kinetic inductance of these films, inherent to disordered materials, allows us to implement ultra-short (200 $\mu$m at a 5GHz resonance frequency) and high-impedance (up to 5 k$\Omega$) half-wavelength resonators. We have shown that the intrinsic losses in these resonators at temperatures $\lesssim 250$ mK are limited by resonator coupling to two-level systems in the environment. The demonstrated internal quality factors are comparable with those for CPW resonators made of conventional superconductors. High kinetic inductance and well-understood losses make these disordered Aluminum resonators promising for a wide range of microwave applications which include kinetic inductance photon detectors and superconducting quantum circuits.