I Quantum nonlocality and entanglement

[Spar]

Wikipedia says

entanglement of a two-party state is necessary but not sufficient for that state to be nonlocal

https://en.m.wikipedia.org/wiki/Quantum_nonlocality#Differences_between_nonlocality_and_entanglement

But isn't wave function collapse nonlocal without any quantum entanglement?

 

[Strilanc]

An electron's wave function can be thought of as being a large entangled state, with a qubit at each point in space that is 1 if the electron is present and 0 otherwise. The qubits are entangled such that only one of them will be 1 at a time (assuming just a single electron is present). Then the "collapse of the wavefunction" translates to "collapse of the large non-local state between all the is-electron-here qubits".

 

[Demystifier]

But isn't wave function collapse nonlocal without any quantum entanglement?

Yes, but there are interpretations of QM without collapse. Some entangled states show that there is some kind of nonlocality even without the collapse.

 

[vanhees71]

It should, however, be stressed that you have "nonlocal" (I'd rather say, "long-ranged") correlations but, according to standard relativistic QFT, no nonlocal interactions. That's of utmost importance to really debunk the original EPR criticism. A collapse assumption is directly contradicting this important principle and thus is inconsistent with the most successful physical theory ever, which is relativistic local QFT.