# High-kinetic inductance NbN films for high-quality compact superconducting resonators

## TL;DR

This paper demonstrates high-quality, compact NbN superconducting resonators with high kinetic inductance, stable performance over time, and potential for scalable quantum circuits.

## Contribution

It introduces NbN thin-film resonators with high internal quality factors and high impedance, suitable for scalable quantum technologies.

## Key findings

- Internal quality factor above 10^5
- High impedance (>2kΩ) in compact footprint
- Stable performance over nine months

## Abstract

Niobium nitride (NbN) is a particularly promising material for quantum technology applications, as entails the degree of reproducibility necessary for large-scale of superconducting circuits. We demonstrate that resonators based on NbN thin films present a one-photon internal quality factor above 10$^5$ maintaining a high impedance (larger than 2k$\Omega$), with a footprint of approximately 50x100 $\mu$m$^2$ and a self-Kerr nonlinearity of few tenths of Hz. These quality factors, mostly limited by losses induced by the coupling to two-level systems, have been maintained for kinetic inductances ranging from tenths to hundreds of pH/square. We also demonstrate minimal variations in the performance of the resonators during multiple cooldowns over more than nine months. Our work proves the versatility of niobium nitride high-kinetic inductance resonators, opening perspectives towards the fabrication of compact, high-impedance and high-quality multimode circuits, with sizable interactions.