High Kinetic Inductance NbN Nanowire Superinductors

TL;DR

This paper demonstrates a high kinetic inductance NbN nanowire superinductor with low microwave loss and high impedance, suitable for quantum circuits, and analyzes its dissipation mechanisms.

Contribution

It introduces a NbN nanowire superinductor with high impedance and low loss, advancing quantum circuit components.

Findings

Impedance exceeds the quantum resistance of ~6.5kΩ.

Single photon quality factor of 2.5×10^4.

Loss mechanisms are explained by two-level system loss.

Abstract

We demonstrate that a high kinetic inductance disordered superconductor can realize a low microwave loss, non-dissipative circuit element with an impedance greater than the quantum resistance ($R_Q = h/4e^2 \simeq 6.5k\Omega$). This element, known as a superinductor, can produce a quantum circuit where charge fluctuations are suppressed. The superinductor consists of a 40 nm wide niobium nitride nanowire and exhibits a single photon quality factor of $2.5 \times 10^4$. Furthermore, by examining loss rates, we demonstrate that the dissipation of our nanowire devices can be fully understood in the framework of two-level system loss.