By use of coincidence measurements on “ultraweak” photon emission, the photocount statistics (PCS) of artificial
visible light turns out to follow—as expected—super-Poissonian PCS. Biophotons, originating from spontaneous or light-induced living systems, display super-Poissonian, Poissonian and even sub-Poissonian PCS. This result shows the first time evidence of non-classical (squeezed) light in living tissues.
