Light transport in PT-invariant photonic structures with hidden   symmetries
  We introduce a recursive bosonic quantization technique for generating classical PT photonic structures that possess hidden symmetries and higher order exceptional points. We study light transport in these geometries and we demonstrate that perfect state transfer is possible only for certain initial conditions. Moreover, we show that for the same propagation direction, left and right coherent transports are not symmetric with field amplitudes following two different trajectories. A general scheme for identifying the conservation laws in such PT-symmetric photonic networks is also presented. 
M.H. Teimourpour, R. El-Ganainy, A. Eisfeld, A. Szameit and D.N   Christodoulides
physics.optics quant-ph