Granular superconductors for high kinetic inductance and low loss quantum devices

TL;DR

This paper demonstrates that nano-scale granular aluminum films can achieve high kinetic inductance and quality factors simultaneously, making them promising for advanced quantum devices.

Contribution

It introduces high-quality granular aluminum films with superior kinetic inductance and low loss, surpassing existing materials for quantum device applications.

Findings

Achieved high kinetic inductance (~10 nH/sq) in granular aluminum films.

Maintained high quality factors alongside high inductance.

Attributed the material's properties to a Mott-type metal-insulator transition.

Abstract

Granular aluminum is a promising material for high kinetic inductance devices such as qubit circuits. It has the advantage over atomically disordered materials such as NbN_x, to maintain a high kinetic inductance concomitantly with a high quality factor. We show that high quality nano-scale granular aluminum films having a sharp superconducting transition with normal state resistivity values of the order of 1x10^5 \mu\Omega cm and kinetic inductance values of the order of 10 nH/sq can be obtained, surpassing state of the art values. We argue that this is a result of the different nature of the metal-to-insulator transition, being electronic correlations driven (Mott type) in the former and disorder driven (Anderson type) in the latter.