Quantum dynamics of an electromagnetic mode that cannot contain N photons
L. Bretheau1,2, P. Campagne-Ibarcq1, E. Flurin1, F. Mallet1, B. Huard1
1 Laboratoire Pierre Aigrain, Ecole Normale Supérieure-PSL Research University, CNRS, Université Pierre et Marie Curie–Sorbonne Universités, Université Paris Diderot–Sorbonne Paris Cité, 24 Rue Lhomond, 75231 Paris, France
Electromagnetic modes are instrumental in building quantum machines. In this experiment , performed in a
circuit Quantum Electrodynamics architecture, 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 a spin N/2. Performing a direct Wigner tomography of the field revealed its nonclassical features, including a Schrödinger 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.
 L. Bretheau, P. Campagne-Ibarcq, E. Flurin, F. Mallet, B. Huard, Science, 348, 776-779 (2015).