Like: when |ψ⟩ is localized to U, it doesn't impact the dynamics of states localized outside U.
So that quantum optics experiments in two countries can ignore each other. And even different arms of the same experiment can ignore each other (you often hear "photon went down this arm of the device")
So that quantum optics experiments in two countries can ignore each other. And even different arms of the same experiment can ignore each other (you often hear "photon went down this arm of the device")
Comments
QFT is an inevitable consequence of the conjunction of
1. QM
2. SR
3. cluster decomposition, i.e. exactly this asymptotic condition
I kind of have a tendency to literature search everything to death whenever I get confused and should probably ask people more questions
How do we ID that a system is in a given state, |x⟩? In my story-book understanding, it's cause we received value x from an X-measurement, so we projected the system into post-state |x⟩. [1]