  The explorations of the quantum-inspired symmetries in optical and photonic
systems have witnessed immense research interests both fundamentally and
technologically in a wide range of subjects of physics and engineering. One of
the principal emerging fields in this context is non-Hermitian physics based on
parity-time symmetry, originally proposed in the studies pertaining to quantum
mechanics and quantum field theory, recently ramified into diverse set of
areas, particularly in optics and photonics. The intriguing physical effects
enabled by non-Hermitian physics and PT symmetry have enhanced significant
applications prospects and engineering of novel materials. In addition, it has
observed increasing research interests in many emerging directions beyond
optics and photonics. This Review paper attempts to bring together the state of
the art developments in the field of complex non-Hermitian physics based on PT
symmetry in various physical settings along with elucidating key concepts and
background and a detailed perspective on new emerging directions. It can be
anticipated that this trendy field of interest can be indispensable in
providing new perspectives in maneuvering the flow of light in the diverse
physical platforms in optics, photonics, condensed matter, opto-electronics and
beyond, and offer distinctive applications prospects in novel functional
materials.
