Charge qubit driven via the Josephson nonlinearity

  1. Jani Tuorila,
  2. Matti Silveri,
  3. Mika Sillanpää,
  4. Erkki Thuneberg,
  5. Yuriy Makhlin,
  6. and Pertti Hakonen
We study the novel nonlinear phenomena that emerge in a charge qubit due to the interplay between a strong microwave flux drive and a periodic Josephson potential. We first analyze
the system in terms of the linear Landau-Zener-St\“uckelberg model, and show its inadequacy in a periodic system with several Landau-Zener crossings within a drive period. Experimentally, we probe the quasienergy levels of the driven qubit with an LC-cavity, which requires the use of linear response theory. We also show that our numerical calculations are in good agreement with the experimental data.