We say that an electron has a dipole moment (let's arbitrarily focus on magnetic dipole moment), which we can calculate classically and also add quantum corrections. Suppose we measure the electron's spin projection. The way we interpret the setup is that we can now calculate the magnetic field generated by the dipole moment.
Does this picture still make sense in QFT? I'm used to think about these things in terms of interactions, Feynman diagrams etc. and less in terms of field configurations. Here's my concrete question:
Will the presence of some exictation in the electron field (i.e. particle), having measured its spin projection, induce a well determined photon field strength?
Somehow I'm less inclined to think that, and more inclined into thinking that you will only increase the probability of interacting with the photon field in a particular way and perhaps emit photon in particular directions.