Nonlinear quantum processes in superconducting resonators terminated by neon-focused-ion-beam-fabricated superconducting nanowires

  1. Jamie A. Potter,
  2. Oscar W. Kennedy,
  3. Jonathan C. Fenton,
  4. and Paul A. Warburton
We have used a neon focused-ion-beam to fabricate both nanoscale Nb Dayem bridges and NbN phase-slip nanowires located at the short-circuited end of quarter-wavelength coplanar waveguide
resonators. The Dayem bridge devices show flux-tunability and intrinsic quality factor exceeding 10,000 at 300 mK up to local fields of at least 60 mT. The NbN nanowires show signatures of incoherent quantum tunnelling of flux at 300 mK.

Low-Loss Superconducting Nanowire Circuits Using a Neon Focused Ion Beam

  1. Jonathan Burnett,
  2. James Sagar,
  3. Oscar W. Kennedy,
  4. Paul A. Warburton,
  5. and Jonathan C. Fenton
We present low-temperature measurements of low-loss superconducting nanowire-embedded resonators in the low-power limit relevant for quantum circuits. The superconducting resonators
are embedded with superconducting nanowires with widths down to 20nm using a neon focused ion beam. In the low-power limit, we demonstrate an internal quality factor up to 3.9×10^5 at 300mK [implying a two-level-system-limited quality factor up to 2×10^5 at 10 mK], not only significantly higher than in similar devices but also matching the state of the art of conventional Josephson-junction-embedded resonators. We also show a high sensitivity of the nanowire to stray infrared photons, which is controllable by suitable precautions to minimize stray photons in the sample environment. Our results suggest that there are excellent prospects for superconducting-nanowire-based quantum circuits.