Daniel Forchheimer

Intermodulation spectroscopy and the nonlinear response of two-level systems in superconducting coplanar waveguide resonators

  1. Janka Biznárová,
  2. J. C. Rivera Hernández,
  3. Daniel Forchheimer,
  4. Jonas Bylander,
  5. David B. Haviland,
  6. and Gustav Andersson
Two-level system (TLS) loss is typically limiting the coherence of superconducting quantum circuits. The loss induced by TLS defects is nonlinear, resulting in quality factors with
a strong dependence on the circulating microwave power. We observe frequency mixing due to this nonlinearity by applying a two-tone drive to a coplanar waveguide resonator and measuring the intermodulation products using a multifrequency lock-in technique. This intermodulation spectroscopy method provides an efficient approach to characterizing TLS loss in superconducting circuits. Using harmonic balance reconstruction, we recover the nonlinear parameters of the device-TLS interaction, which are in good agreement with the standard tunnelling model for TLSs.
arxiv pdf