Spontaneous generation of photons in transmission of quantum fields in PT-symmetric optical systems

We develop a rigorous, mathematically consistent description of PT-symmetric optical systems by using second quantization. We demonstrate the possibility of significant spontaneous generation of photons in PT-symmetric systems. Further, we show the emergence of Hanbury Brown-Twiss correlations in spontaneous generation. We show that the spontaneous generation determines decisively the nonclassical nature of fields in PT-symmetric systems. Our work can be applied to other systems, such as plasmonic structures, where losses are compensated by gain mechanisms.