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

We characterize niobium nitride (NbN) $λ/2$ coplanar waveguide resonators, which were fabricated from a 10nm thick film on silicon dioxide grown by sputter deposition. For films grown at 120°C we report a superconducting critical temperature of 7.4K associated with a normal square resistance of 1k$Ω$ leading to a kinetic inductance of 192pH/$\Box$. We fabricated resonators with a characteristic impedance up to 4.1k$Ω$ 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.

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