High Impedance Granular Aluminum Ring Resonators

  1. Mahya Khorramshahi,
  2. Martin Spiecker,
  3. Patrick Paluch,
  4. Simon Geisert,
  5. Nicolas Gosling,
  6. Nicolas Zapata,
  7. Lucas Brauch,
  8. Christian Kübel,
  9. Simone Dehm,
  10. Ralph Krupke,
  11. Wolfgang Wernsdorfer,
  12. Ioan M. Pop,
  13. and Thomas Reisinger
Superconducting inductors with impedance surpassing the resistance quantum, i.e., superinductors, are important for quantum technologies because they enable the development of protected qubits, enhance coupling to systems with small electric dipole moments, and facilitate the study of phase-slip physics. We demonstrate superinductors with densely packed meandered traces of granular aluminum (grAl) with inductances up to 4μH, achieving impedances exceeding 100kΩ in the 4−8GHz range. Ring resonators made with grAl meandered superinductors exhibit quality factors on the order of 105 in the single-photon regime and low non-linearity on the order of tens of Hz. Depending on the grAl resistivity, at 10Hz, we measure frequency noise spectral densities in the range of 102 to 103Hz/Hz‾‾‾√. In some devices, in the single-photon regime, we observe a positive Kerr coefficient of unknown origin. Using more complex fabrication, the devices could be released from the substrate, either freestanding or suspended on a membrane, thereby further improving their impedance by a factor of three.
arxiv pdf

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