basically, for H for a "single deuterium atom", in a truncated H space, we can have a wave function/Hamiltonian for it, because Hs (interaction part, the "electromagnetic electron-nucleus interaction") is relatively small, relative to the other part of/or whole "system", this relativeness is "analogous to what Tononi calls \the cruelest cut")", or 整体大于部分的 Hamiltonian;

when dealing with system like that, quantum physics works,
"动量 and 位置"整体上是对应的，确定的，平方可积，有测度