Magnetic field resilient high kinetic inductance superconducting niobium nitride coplanar waveguide resonators

TL;DR

This paper reports on niobium nitride coplanar waveguide resonators that maintain high quality factors under strong magnetic fields, making them suitable for quantum experiments in magnetic environments.

Contribution

The study demonstrates the fabrication and characterization of NbN resonators with high magnetic field resilience and high characteristic impedance, advancing their application in quantum technologies.

Findings

Resonators achieve $Q_i > 10^4$ at zero magnetic field.

Resonators maintain $Q_i > 10^4$ in 6T in-plane magnetic field.

Resonators sustain $Q_i > 10^4$ in 300mT out-of-plane magnetic field.

Abstract

We characterize niobium nitride (NbN) $\lambda/2$ coplanar waveguide resonators, which were fabricated from a 10nm thick film on silicon dioxide grown by sputter deposition. For films grown at 120{\deg}C we report a superconducting critical temperature of 7.4K associated with a normal square resistance of 1k$\Omega$ leading to a kinetic inductance of 192pH/$\Box$. We fabricated resonators with a characteristic impedance up to 4.1k$\Omega$ and internal quality factors $Q_\mathrm{i} > 10^4$ in the single photon regime at zero magnetic field. Moreover, in the many photons regime, the resonators present high magnetic field resilience with $Q_\mathrm{i} > 10^4$ in a 6T in-plane magnetic field as well as in a 300mT out-of-plane magnetic field. These findings make such resonators a compelling choice for cQED experiments involving quantum systems with small electric dipole moments operated in finite magnetic fields.