R. Pilipenko

Disentangling the sources of ionizing radiation in superconducting qubits

  1. L. Cardani,
  2. I. Colantoni,
  3. A. Cruciani,
  4. F. De Dominicis,
  5. G. D'Imperio,
  6. M. Laubenstein,
  7. A. Mariani,
  8. L. Pagnanini,
  9. S. Pirro,
  10. C. Tomei,
  11. N. Casali,
  12. F. Ferroni,
  13. D. Frolov,
  14. L. Gironi,
  15. A. Grassellino,
  16. M. Junker,
  17. C. Kopas,
  18. E. Lachman,
  19. C.R.H. McRae,
  20. J. Mutus,
  21. M. Nastasi,
  22. D. P. Pappas,
  23. R. Pilipenko,
  24. M. Sisti,
  25. V. Pettinacci,
  26. A. Romanenko,
  27. D. Van Zanten,
  28. M. Vignati,
  29. J. D. Withrow,
  30. and N. Z. Zhelev
Radioactivity was recently discovered as a source of decoherence and correlated errors for the real-world implementation of superconducting quantum processors. In this work, we measure
levels of radioactivity present in a typical laboratory environment (from muons, neutrons, and gamma’s emitted by naturally occurring radioactive isotopes) and in the most commonly used materials for the assembly and operation of state-of-the-art superconducting qubits. We develop a GEANT-4 based simulation to predict the rate of impacts and the amount of energy released in a qubit chip from each of the mentioned sources. We finally propose mitigation strategies for the operation of next-generation qubits in a radio-pure environment.
arxiv pdf

High quality superconducting Nb co-planar resonators on sapphire substrate

  1. S. Zhu,
  2. F. Crisa,
  3. M. Bal,
  4. A. A. Murthy,
  5. J. Lee,
  6. Z. Sung,
  7. A. Lunin,
  8. D. Frolov,
  9. R. Pilipenko,
  10. D. Bafia,
  11. A. Mitra,
  12. A. Romanenko,
  13. and A. Grassellino
We present measurements and simulations of superconducting Nb co-planar waveguide resonators on sapphire substrate down to millikelvin temperature range with different readout powers.
In the high temperature regime, we demonstrate that the Nb film residual surface resistance is comparable to that observed in the ultra-high quality, bulk Nb 3D superconducting radio frequency cavities while the resonator quality is dominated by the BCS thermally excited quasiparticles. At low temperature both the resonator quality factor and frequency can be well explained using the two-level system models. Through the energy participation ratio simulations, we find that the two-level system loss tangent is ∼10−2, which agrees quite well with similar studies performed on the Nb 3D cavities.
arxiv pdf

Three-dimensional superconducting resonators at T<20 mK with the photon lifetime up to τ=2 seconds

  1. A. Romanenko,
  2. R. Pilipenko,
  3. S. Zorzetti,
  4. D. Frolov,
  5. M. Awida,
  6. S. Posen,
  7. and A. Grassellino
Very high quality factor superconducting radio frequency cavities developed for accelerators can offer a path to a 1000-fold increase in the achievable coherence times for cavity-stored
quantum states in the 3D circuit QED architecture. Here we report the first measurements of several accelerator cavities of f_0=1.3, 2.6, 5 GHz resonant frequencies down to temperatures of about 10~mK and field levels down to a few photons, which reveal record high photon lifetimes up to 2 seconds, while also further exposing the role of the two level systems (TLS) in the niobium oxide. We also demonstrate how the TLS contribution can be greatly suppressed by the special vacuum heat treatment.
arxiv pdf