Numerical simulations of Josephson Traveling Wave Parametric Amplifiers (JTWPAs): comparative study of open-source tools

  1. A. Yu. Levochkina,
  2. H. G. Ahmad,
  3. P. Mastrovito,
  4. I. Chatterjee,
  5. D. Massarotti,
  6. D. Montemurro,
  7. F. Tafuri,
  8. G.P. Pepe,
  9. and M. Esposito
Josephson Traveling Wave Parametric Amplifiers (JTWPAs) are largely exploited in quantum technologies for their broadband and low noise performance in the microwave regime. When one
or more microwave tones are applied at the input, such devices show a complex wave-mixing response due to their intrinsic nonlinear nature. Numerical simulations of the JTWPAs nonlinear behaviour provide useful insights not only for the design of such devices, but also for the interpretation and validation of the experimental results. Here we present and discuss a comparative analysis of different open-source tools which can be used for JTWPAs numerical simulations. We focus on two tools for transient simulations, WRSPICE and PSCAN2, and on one tool for direct simulation of the frequency domain behaviour, JosephsonCircuit.jl. We describe the working principle of these three tools and test them considering as a benchmark a JTWPA based on SNAILs (Superconducting Nonlinear Asymmetric Inductive eLement) with realistic experimental parameters. Our results can serve as a guide for numerical simulations of JTWPAs with open-source tools, highlighting advantages and disadvantages depending on the simulation tasks.

Fast tunable high Q-factor superconducting microwave resonators

  1. S. Mahashabde,
  2. E. Otto,
  3. D. Montemurro,
  4. S. de Graaf,
  5. S. Kubatkin,
  6. and A. Danilov
We present fast tunable superconducting microwave resonators fabricated from planar NbN on a sapphire substrate. The 3λ/4 wavelength resonators are tuning fork shaped and tuned by
passing a dc current which controls the kinetic inductance of the tuning fork prongs. The λ/4 section from the open end operates as an integrated impedance converter which creates a nearly perfect short for microwave currents at the dc terminal coupling points, thus preventing microwave energy leakage through the dc lines. We measure an internal quality factor Qint>105 over the entire tuning range. We demonstrate a tuning range of >3% and tuning response times as short as 20 ns for the maximum achievable detuning. Due to the quasi-fractal design, the resonators are resilient to magnetic fields of up to 0.5 T.