Quantum entanglement : need explanation

I proposed on August 21, 2014 a single-photon source that isn't good enough. Within the considered time frame, it emits a photon with a small probability e, but it can also emit two photons with e² probability, and this is too much.

With the source and setup I described, the observations could even be explained with no photons at all. It would suffice to attribute to the target fermions (like electrons in a photodiode) a probability e to get excited by light of that intensity (understood as a field without quanta) and the probability of observing an excitation at both detectors would be e².

To make photons patent, the setup demands a source that has zero probability, not e², to emit two photons. That's why experimenters use sources like single atoms (for instance a nitrogen atom in a diamond crystal) rather than the attenuated diode I had proposed.

Then, if never observing two simultaneous excitations at the detectors, we have some reasons to say the photon, and check with additional hardware that the photon takes both paths but excites only one detector.

Sidenote: this particular setup would leave other interpretations open. Light could have no quanta, provided that the emitting and detecting fermions have some separate means to coordinate themselves. Such interpretations get increasingly complicated if the emitting fermion has disappeared before a detector gets excited. They are not mainstream, but legitimate attempts.