Evidence of ultra-high kinetic inductance near the tunable superconductor-insulator transition in niobium nitride

An inductor with low dissipation, high impedance, and high linearity is a crucial element for superconducting circuits, such as the fluxonium. An alternative approach to junction arrays involves using materials with low Cooper pair density to achieve high kinetic inductance which offers more flexible designs; however, these materials typically suffer from increased dissipation. Here, we demonstrate high kinetic inductance resonators that maintain a single-photon internal quality factor exceeding one million. We achieve high kinetic inductance by tuning the thickness of niobium nitride (NbN) films with atomic precision and find linear dependence on film normal state resistance in agreement with the Mattis-Bardeen relation.