Weyl Josephson Circuits

  1. Valla Fatemi,
  2. Anton R. Akhmerov,
  3. and Landry Bretheau
We introduce Weyl Josephson circuits: small Josephson junction circuits that simulate Weyl band structures. We first formulate a general approach to design circuits that are analogous
to Bloch Hamiltonians of a desired dimensionality and symmetry class. We then construct and analyze a six-junction device that produces a 3D Weyl Hamiltonian with broken inversion symmetry and in which topological phase transitions can be triggered \emph{in situ}. We argue that currently available superconducting circuit technology allows experiments that probe topological properties inaccessible in condensed matter systems.

Quantum dynamics of an electromagnetic mode that cannot contain N photons

  1. Landry Bretheau,
  2. Philippe Campagne-Ibarcq,
  3. Emmanuel Flurin,
  4. François Mallet,
  5. and Benjamin Huard
Electromagnetic modes are instrumental in building quantum machines. In this experiment, we introduce a method to manipulate these modes by effectively controlling their phase space.
Preventing access to a single energy level, corresponding to a number of photons N, confined the dynamics of the field to levels 0 to N-1. Under a resonant drive, the level occupation was found to oscillate in time, similarly to an N-level system. Performing a direct Wigner tomography of the field revealed its nonclassical features, including a Schr\“{o}dinger cat-like state at half period in the evolution. This fine control of the field in its phase space may enable applications in quantum information and metrology.