A V-shape superconducting artificial atom based on two inductively coupled transmons

  1. É. Dumur,
  2. B. Küng,
  3. A. K. Feofanov,
  4. T. Weissl,
  5. N. Roch,
  6. C. Naud,
  7. W. Guichard,
  8. and O. Buisson
Circuit quantum electrodynamics systems are typically built from resonators and two-level artificial atoms, but the use of multi-level artificial atoms instead can enable promising
applications in quantum technology. Here we present an implementation of a Josephson junction circuit dedicated to operate as a V-shape artificial atom. Based on a concept of two internal degrees of freedom, the device consists of two transmon qubits coupled by an inductance. The Josephson nonlinearity introduces a strong diagonal coupling between the two degrees of freedom that finds applications in quantum non-demolition readout schemes, and in the realization of microwave cross-Kerr media based on superconducting circuits.