Rabi Oscillations at Exceptional Points in Microwave Billiards
  We experimentally investigated the decay behavior with time t of resonances near and at exceptional points, where two complex eigenvalues and also the associated eigenfunctions coalesce. The measurements were performed with a dissipative microwave billiard, whose shape depends on two parameters. The t^2-dependence predicted at the exceptional point on the basis of a two-state matrix model could be verified. Outside the exceptional point the predicted Rabi oscillations, also called quantum echoes in this context, were detected. To our knowledge this is the first time that quantum echoes related to exceptional points were observed experimentally. 
B. Dietz, T. Friedrich, J. Metz, M. Miski-Oglu, A. Richter, F.   Sch\"afer, C. A. Stafford