Experimental observation of dynamical blockade between transmon qubits via ZZ interaction engineering

  1. Marco Riccardi,
  2. Aviv Glezer Moshe,
  3. Guido Menichetti,
  4. Riccardo Aiudi,
  5. Carlo Cosenza,
  6. Ashkan Abedi,
  7. Roberto Menta,
  8. Halima Giovanna Ahmad,
  9. Diego Nieri Orfatti,
  10. Francesco Cioni,
  11. Davide Massarotti,
  12. Francesco Tafuri,
  13. Vittorio Giovannetti,
  14. Marco Polini,
  15. Francesco Caravelli,
  16. and Daniel Szombati
We report the experimental realization of strong longitudinal (ZZ) coupling between two superconducting transmon qubits achieved solely through capacitive engineering. By systematically
varying the qubit frequency detuning, we measure cross-Kerr inter-qubit interaction strengths ranging from 10 MHz up to 350 MHz, more than an order of magnitude larger than previously observed in similar capacitively coupled systems. In this configuration, the qubits enter a strong-interaction regime in which the excitation of one qubit inhibits that of its neighbor, demonstrating a dynamical blockade mediated entirely by the engineered ZZ coupling. Circuit quantization simulations accurately reproduce the experimental results, while perturbative models confirm the theoretical origin of the energy shift as a hybridization between the computational states and higher-excitation manifolds. We establish a robust and scalable method to access interaction-dominated physics in superconducting circuits, providing a pathway towards solid-state implementations of globally controlled quantum architectures and cooperative many-body dynamics.

Granular superconductors for high kinetic inductance and low loss quantum devices

  1. Aviv Glezer Moshe,
  2. Eli Farber,
  3. and Guy Deutscher
Granular aluminum is a promising material for high kinetic inductance devices such as qubit circuits. It has the advantage over atomically disordered materials such as NbN_x, to maintain
a high kinetic inductance concomitantly with a high quality factor. We show that high quality nano-scale granular aluminum films having a sharp superconducting transition with normal state resistivity values of the order of 1×10^5 \mu\Omega cm and kinetic inductance values of the order of 10 nH/sq can be obtained, surpassing state of the art values. We argue that this is a result of the different nature of the metal-to-insulator transition, being electronic correlations driven (Mott type) in the former and disorder driven (Anderson type) in the latter.