# Is pair production instantaneous?

I was just reading this question and I didn't understand the question at first. But I think I understood it after a bit of thought. Here is my question inspired from that question:

Are the processes of pair production and matter-antimatter annihilation instantaneous? If not, what are the intermediate forms of matter-energy involved in the process?

NOTE: I don't know exactly how weird quantum mechanics is. But is the answer that there is no sense of instantaneous at the sub-atomic level?

Although the question is about QED, I don't think the answer is really very different from the answer we would have for any quantum-mechanical process involving a decay or transition. You have a state vector that starts out as $|1\rangle$ and then then evolves into $c_1|1\rangle+c_2|2\rangle$. As time goes on, $|c_2|$ increases. The evolution is smooth and deterministic, and is described by the Schrödinger equation. There are no sudden jumps.