Nanometric constrictions in superconducting coplanar waveguide resonators

TL;DR

This paper presents the design, fabrication, and characterization of superconducting coplanar waveguide resonators with nanoscopic constrictions, enabling enhanced magnetic field concentration for quantum and magnetic sensing applications.

Contribution

It introduces nanometric constrictions in superconducting resonators and analyzes their effects on device performance and potential for quantum technology applications.

Findings

Resonance frequency changes are below 1% with constrictions.

Internal quality factors remain comparable to original devices.

Nanoscopic constrictions increase magnetic field concentration near the center line.

Abstract

We report on the design, fabrication and characterization of superconducting coplanar waveguide resonators with nanoscopic constrictions. By reducing the size of the center line down to 50 nm, the radio frequency currents are concentrated and the magnetic field in its vicinity is increased. The device characteristics are only slightly modified by the constrictions, with changes in resonance frequency lower than 1% and internal quality factors of the same order of magnitude as the original ones. These devices could enable the achievement of higher couplings to small magnetic samples or even to single molecular spins and have applications in circuit quantum electrodynamics, quantum computing and electron paramagnetic resonance.