Comment by cfgauss2718

In quantum field theory (standard model of particle physics), photons are the quanta of a field (naturally identified with the quantized electromagnetic field, or U(1) gauge field), which evolves in a nonlinear way that is coupled not only to itself, but also the electron field (as photons are the carrier of the electromagnetic interaction). It seems to me that the concept of “photon” (the particle) is one that is useful in some contexts (like modeling the possible interactions between two electrons in a Feynman diagram), but that the concept of photon is not a fundamental constituent of reality. Certainly, wave packets of the field can interact by way of superposition and thereby altering the space-time evolution of the field through its coupling constant.