D. J. Reilly

Josephson Junctions Via Anodization of Epitaxial Al on an InAs Heterostructure

  1. A. Jouan,
  2. J. D. S. Witt,
  3. G. C. Gardner,
  4. C. Thomas,
  5. T. Lindemann,
  6. S. Gronin,
  7. M. J. Manfra,
  8. and D. J. Reilly
We combine electron beam lithography and masked anodization of epitaxial aluminium to define tunnel junctions via selective oxidation, alleviating the need for wet-etch processing or
direct deposition of dielectric materials. Applying this technique to define Josephson junctions in proximity induced superconducting Al-InAs heterostructures, we observe multiple Andreev reflections in transport experiments, indicative of a high quality junction. We further compare the mobility and density of Hall-bars defined via wet etching and anodization. These results may find utility in uncovering new fabrication approaches to junction-based qubit platforms.
arxiv pdf

Superconducting Resonators with Parasitic Electromagnetic Environments

  1. J. M. Hornibrook,
  2. E. E. Mitchell,
  3. and D. J. Reilly
Parasitic electromagnetic fields are shown to strongly suppress the quality (Q)-factor of superconducting coplanar waveguide resonators via non-local dissipation in the macroscopic
environment. Numerical simulation and low temperature measurements demonstrate how this parasitic loss can be reduced, establishing a Lorentzian lineshape in the resonator frequency response and yielding a loaded Q-factor of 2.4 x 10^5 for niobium devices on sapphire substrates. In addition, we report the dependence of the Q and resonance frequency shift Delta f_0 with input power and temperature in the limit where loss from two-level systems in the dielectric dominate.
arxiv pdf