I am trying to resolve a paradox in my head, and I call upon the forums to help. Consider two identical photons traveling, each with E=hf, so the total energy is 2hf. Now, by whatever method, the photons are made to travel right on top of each other, with one being perfectly out of phase with the other. Their amplitude vanishes. What happens to the energy? An electromagnetic wave with zero amplitude has zero energy (it is just empty space). For that matter, what happens to the photons? Can we expect them to be recovered from such a situation?