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.
@article{arxiv.1409.1040,
title = {Nanometric constrictions in superconducting coplanar waveguide resonators},
author = {Mark David Jenkins and Uta Naether and Miguel Ciria and Javier Sesé and James Atkinson and Carlos Sánchez-Azqueta and Enrique del Barco and Johannes Majer and David Zueco and Fernando Luis},
journal= {arXiv preprint arXiv:1409.1040},
year = {2016}
}