Emergent Harmonics in Josephson Tunnel Junctions Due to Series Inductance

  1. Junghyun Kim,
  2. Max Hays,
  3. Ilan T. Rosen,
  4. Junyoung An,
  5. Helin Zhang,
  6. Aranya Goswami,
  7. Kate Azar,
  8. Jeffrey M. Gertler,
  9. Bethany M. Niedzielski,
  10. Mollie E. Schwartz,
  11. Terry P. Orlando,
  12. Jeffrey A. Grover,
  13. Kyle Serniak,
  14. and William D. Oliver
Josephson tunnel junctions are essential elements of superconducting quantum circuits. The operability of these circuits presumes a 2π-periodic sinusoidal potential of a tunnel junction, but higher-order corrections to this Josephson potential, often referred to as „harmonics,“ cause deviations from the expected circuit behavior. Two potential sources for these harmonics are the intrinsic current-phase relationship of the Josephson junction and the inductance of the metallic traces connecting the junction to other circuit elements. Here, we introduce a method to distinguish the origin of the observed harmonics using nearly-symmetric superconducting quantum interference devices (SQUIDs). Spectroscopic measurements of level transitions in multiple devices reveal features that cannot be explained by a standard cosine potential, but are accurately reproduced when accounting for a second-harmonic contribution to the model. The observed scaling of the second harmonic with Josephson-junction size indicates that it is due almost entirely to the trace inductance. These results inform the design of next-generation superconducting circuits for quantum information processing and the investigation of the supercurrent diode effect.
arxiv pdf

leave comment