The thing is, they’re not truly independent because the particles were prepared so as to already be entangled—the part of Fock space you put the system (and thus yourself) in is one where the particles are already aligned relative to each other, even though no one particular absolute alignment is preferred. If you entangle yourself with one, then you find you’re already entangled with the other.
Right, the two macroscopic systems are entangled once both interact with the singlet, but this is a non-local statement which acts as a curiosity stopper, since it does not provide any local mechanism for the apparent “action at a distance”. Presumably MWI would offer something better than shut-up-and-calculate, like showing how what is seen locally as a pair of worlds at each detector propagate toward each other, interact and become just two worlds at the point where the results are compared, thanks to the original correlations present when the singlet was initially prepared. Do you know of anything like that written up anywhere?
Part 1 - to your first sentence: If you accept quantum mechanics as the one fundamental law, then state information is already nonlocal. Only interactions are local. So, the way you resolve the apparent ‘action at a distance’ isn’t to deny that it’s nonlocal, but to deny that it’s an action. To be clearer:
Some events transpire locally, that determine which (nonlocal) world you are in. What happened at that other location? Nothing.
Part 2 - Same as last link, question 32., with one exception: I would say that |me(L)> and such, being macrostates, do not represent single worlds but thermodynamically large bundles of worlds that share certain common features. I have sent an email suggesting this change (but considering the lack of edits over the last 18 years, I’m not confident that it will happen).
To summarize: just forget about MWI and use conventional quantum mechanics + macrostates. The entanglement is infectious, so each world ends up with an appropriate pair of measurements.
Right, the two macroscopic systems are entangled once both interact with the singlet, but this is a non-local statement which acts as a curiosity stopper, since it does not provide any local mechanism for the apparent “action at a distance”. Presumably MWI would offer something better than shut-up-and-calculate, like showing how what is seen locally as a pair of worlds at each detector propagate toward each other, interact and become just two worlds at the point where the results are compared, thanks to the original correlations present when the singlet was initially prepared. Do you know of anything like that written up anywhere?
Part 1 - to your first sentence: If you accept quantum mechanics as the one fundamental law, then state information is already nonlocal. Only interactions are local. So, the way you resolve the apparent ‘action at a distance’ isn’t to deny that it’s nonlocal, but to deny that it’s an action. To be clearer:
Some events transpire locally, that determine which (nonlocal) world you are in. What happened at that other location? Nothing.
Part 2 - Same as last link, question 32., with one exception: I would say that |me(L)> and such, being macrostates, do not represent single worlds but thermodynamically large bundles of worlds that share certain common features. I have sent an email suggesting this change (but considering the lack of edits over the last 18 years, I’m not confident that it will happen).
To summarize: just forget about MWI and use conventional quantum mechanics + macrostates. The entanglement is infectious, so each world ends up with an appropriate pair of measurements.