Photon-photon interactions

Question

I know that photons don't directly interact with one another, but in the context of the double slit experiment they can interact to give an interference pattern. This seems like a contradiction to me. Can you help me understand this?

Answer 1

If 1000 scientists each did the DSE with only one photon each .... if/when they had a conference to discuss/combine results ... yes indeed the pattern would be present! Every photon does its own thing.... the DSE apparatus has "modes" like any other optical experiment, modes are resonant pathways of the EM field.

Answer 2

PhysicsDave: the DSE apparatus has "modes" like any other optical experiment, modes are resonant pathways of the EM field.

Experiments were carried out - as early as the early 1900s - in which electrons were influenced by a biprism. This is a wire behind which an electron beam has a fringe-shaped intensity distribution. It should come as no surprise that applying a voltage to the wire changes the width of the fringes.

A photon is a particle that is indivisible between emission and absorption. Photons are also diffracted at individual edges and the statistics of single photon firing also show fringe-shaped intensity distributions behind edges and even more so behind slits.

Rick: I know that photons don't directly interact with one another, but in the context of the double slit experiment they can interact to give an interference pattern

Interference for water waves also means that the entire energy of the two waves is dissipated in a destructive interference. This process is not possible for - at least low-energy - photons. As you have already said, the photons do not interact. It is therefore impossible to speak of interference. Instead, one should use the term diffraction.

Then the question remains as to what causes the diffraction. For lack of a better understanding, Young's idea of interference between the particles or of the particle on itself is still used here.

However, a new approach (Gedankenansatz) would not be wrong, in which the interaction of the particle with the surface electrons of the edge(s) is taken into consideration. All the more so since phonon excitations in bodies represent a broad field of research (including stealth technology). This would involve the interaction of the magnetic and electric field components of the electrons with those of the photon.