I get the notion that an elementary particle derives from a localized perturbation of that particles quantum field. What I don't get is how that perturbation can lead to two alternative quantum states for that particle - for example, an electron with two spin states (spin up and spin down). Are there two alternate perturbation states for an electron's quantum field. (spin up and spin down) or is there a single field perturbation that devolves randomly to either a spin up or spin down quantum state. I am not even sure that I am thinking about spin states in the right way. Would appreciate an explanation.