In a single photon at a time double slit experiment. Is it the wave function or electromagnetic wave of a photon that is interfering? If both, what is the contribution of each? Remember that the electromagnetic wave is not the wave function of the photon. In a single photon, it has wave function, electromagnetic wave, and quantum field. How large is the electromagnetic wave of a single photon and how large is the quantum field? And what is the difference between it? Can anyone point to a site with an illustration or something? I want to be conversant with a photon properties first because in QFT, they are said to make a leap of faith that since photon and electron and other particle are fundamental particles. They should be the same, hence Second Quantization is invoked for electron where just like the photons they are field quanta of their respective quantum field (electron quantum field for example). This is due to the electromagnetic field successfully applied with canonical quantization producing the field quanta or photons. So they applied it to all particles even if they don't have any electromagnetic field. The success of QED gave them the confidence to go on in their leap of faith. In a single electron at a time double slit experiment, We can't assume only the wave function is present. There must be a corresponding quantum field associated with it. In a photon, it has properties of magnetic field and electric field producing electromagnetic field. Maybe this is why its quantum field (which is simply the electromagnetic field) can be detected? I heard there is an equivalent in the electron field. So what would it take to measure the electron field (or matter field)?