Experimental simulation of symmetry-protected higher-order exceptional points with single photons.

The article focuses on the study of exceptional points (EPs) in non-Hermitian (NH) systems. It is reported that EPs are branch point singularities in the parameter space and are associated with the dispersion of interface states. It is further reported that these EPs has interesting topological properties and find applications in various areas, including sensing, wave propagation, laser emission, and more.