Observation of a Chiral State in a Microwave Cavity
  A microwave experiment has been realized to measure the phase difference of the oscillating electric field at two points inside the cavity. The technique has been applied to a dissipative resonator which exhibits a singularity -- called exceptional point -- in its eigenvalue and eigenvector spectrum. At the singularity, two modes coalesce with a phase difference of $\pi/2 .$ We conclude that the state excited at the singularity has a definitiv chirality. 
C. Dembowski (1), B. Dietz (1), H.-D. Graef (1), H. L. Harney (2), A.   Heine (1), W. D. Heiss (3), A. Richter (1) ((1) Inst...