Single photons cannot be extracted from the light of multi-atom light sources - art. no. 66640B

Throughout the development and confirmation of the photon concept "Gedankenexperiments" have been invoked where a light source is attenuated until "only one photon is in the apparatus". Such a statement requires, however, knowledge on details of the light generation process, which were not known until the advent of true single - photon light sources such as isolated single atoms or molecules. Here, starting from a two atom light source, it is shown that probably multi - atom or multi - molecule light sources do not generate, even not in small fractions, antibunching photons and that attenuation down to one photon per time unit is not reliably possible. Thus, one of the strongest arguments in favour of the existence of single "photons" in free space, the accumulation time argument, which discusses the absorption of a single photon by a single atom or molecule, becomes questionable.