High-impedance superconducting resonators and on-chip filters for circuit quantum electrodynamics with semiconductor quantum dots

Spin-photon coupling presents an enticing opportunity for the long-range coupling of spin qubits. The spin-photon coupling rate, gs, is proportional to the charge-photon coupling rate, gc. To move deeper into the strong-coupling regime, gc can be enhanced by fabricating high-impedance cavities using high-kinetic-inductance films. Here, we report dc transport and microwave response investigations of niobium nitride (NbN) films of different thicknesses. The kinetic inductance increases rapidly as the film thickness is reduced below 50 nm and for 15-nm NbN films we measure a sheet kinetic inductance Lk,S=41.2pH/ - . As an application of the high-kinetic-inductance films, we fabricate compact LC filters that are commonly used to reduce microwave leakage in circuit quantum electrodynamics (cQED) devices. These filters feature up to 60 dB of attenuation near typical cavity resonance frequencies of fc=8 GHz.