Nanometric constrictions in superconducting coplanar waveguide resonators

  1. Mark David Jenkins,
  2. Uta Naether,
  3. Miguel Ciria,
  4. Javier Sesé,
  5. James Atkinson,
  6. Carlos Sánchez-Azqueta,
  7. Enrique del Barco,
  8. Johannes Majer,
  9. David Zueco,
  10. and Fernando Luis
We report on the design, fabrication and characterization of superconducting coplanar waveguide resonators with nanometric constrictions. By reducing the size of the center line down
to 50 nm, the RF currents are concentrated into a small cross section 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 changes in transmission and Q-factor lower than 20%. 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.