[elektropionir]

I don't think there is consensus that decoherence = measurement. This is a sophisticated experiment that controls the level of position information being "radiated" to the environment. But Born's rule and the measurement postulate are still baked into the fact that you are then measuring the interference pattern.

One thing I never quite understood about the decoherence argument for resolving the measurement problem is that it forces the "collapse" to happen with local interactions. This of course makes sense since you want to think of a measurement as a "normal", unitary process. This means the environment has to "enact" the projection operator through interactions. If you have the most basic EPR pair, how can this happen? How can you decohere the wave function of the spacelike separated counterpart (B) by locally measuring the other spin (A) and then letting the environment project out the state of B through local interactions? In this experiment https://arxiv.org/pdf/1511.03190.pdf they have two detectors 60 meters apart in a subbasement of a castle. What are the interactions in those hallways that are carrying the correlation from the decoherence/measurement on one side of the experiment to the other, faster than light to maintain the correlations. This seems too basic of a question so I don't know if I'm just missing something obvious, but to me it seems like a pretty straightforward argument that the collapse cannot happen through decoherence. I've only dug out one random paper that mentioned this argument with very little subsequent referencing of it.

[AgentME]

Certain experiments have shown that quantum mechanics is incompatible with local realism, and this means either that locality is wrong, and the world has faster-than-light communication, or that realism is wrong, and that there are no single outcomes to events. Assuming that locality is true and realism is wrong, when you measure particle 1, it's not that the result is being instantly communicated to particle 2 and causing it to come out that way, but all possible outcomes for each particle measurement happen separately, and all versions of things affected by particle 1's measurement only interact with versions of the world where particle 2 has or will have a compatible measurement. No collapse ever happens, though from each of the perspectives of humans inside the superposition, they will see results that look like their own measurement caused a collapse, because they each will eventually see a single consistent outcome for the results of the particles' spins.

The results of nonlocal and nonrealism theories come out the same, though nonlocal theories imply a lot of mysteries around the contradiction between instant communication and relativity of simultaneity, while nonrealism just paints a picture of a MWI universe that's surprisingly larger than our expectations.