Band engineering and study of disorder using topology in compact high kinetic inductance cavity arrays

TL;DR

This paper introduces a compact superconducting cavity array with high kinetic inductance that reduces device size, exhibits multiple bandgaps, and allows precise disorder measurement using topological modes, advancing scalable quantum technologies.

Contribution

The work presents a novel high-impedance, miniaturized cavity array architecture with engineered bandgaps and a quantitative method to analyze disorder via topological modes.

Findings

Achieved high-impedance cavity arrays with up to 100 resonators.

Demonstrated multiple bandgaps in the array.

Quantified resonator frequency scattering at approximately 0.22%.

Abstract

Superconducting microwave metamaterials offer enormous potential for quantum optics and information science, enabling the development of advanced quantum technologies for sensing and amplification. In the context of circuit quantum electrodynamics, such metamaterials can be implemented as coupled cavity arrays (CCAs). In the continuous effort to miniaturize quantum devices for increasing scalability, minimizing the footprint of CCAs while preserving low disorder becomes paramount. In this work, we present a compact CCA architecture leveraging superconducting NbN thin films presenting high kinetic inductance, which enables high-impedance CCA ($\sim1.5$ k$\Omega$), while reducing the resonator footprint. We demonstrate its versatility and scalability by engineering one-dimensional CCAs with up to 100 resonators and exhibiting multiple bandgaps. Additionally, we quantitatively investigate disorder in the CCAs using symmetry-protected topological SSH modes, from which we extract a resonator frequency scattering of $0.22^{+0.04}_{-0.03}\%$. Our platform opens up exciting new prospects for analog quantum simulations of many-body physics with ultrastrongly coupled emitters.