4 ms·

In true collapse-of-the-gaps style, what if collapse happens when an entangled system becomes so large that the edges of it are outside of each others event hor

by im3w1l 4y ago

In true collapse-of-the-gaps style, what if collapse happens when an entangled system becomes so large that the edges of it are outside of each others event horizons due to cosmic inflation?

bowsamic 4y ago
I think you mean expansion rather than inflation (inflation is something that happened very briefly at the beginning of the universe). In models with collapse, the collapse happens instantaneously, no matter what
- cb321 4y ago
  As with any unsettled questions there are pros & cons to the various takes on quantum reality. Part of the appeal of MWI (intrication of observer into observed system as part of the measurement process) to me was always that the instantaneousness you mention here is a very "ordinary" kind of "fastness by synchronization". It's basically just a kind of causal wavefront hitting. There are plenty of "infinitely fast" synchronization effects like this..some perhaps less obvious than others, but many pretty pedestrian and accessible to lay people. Neither the junction of a scissors or the "spot light" on clouds need be constrained by light speed, for example. People routinely abuse "nothing" (or maybe "go") in the " 'nothing' can 'go' faster than light" saying. :-)
  - kgwgk 4y ago
    > intrication of observer into observed system as part of the measurement process That was already part of von Neumann’s model of measurement over 90 years ago.
    - cb321 4y ago
      Yeah. Perhaps most charmingly treated here: https://arxiv.org/abs/2011.12671 https://arxiv.org/abs/2011.12671 { EDIT: though surely many other places! There are also YouTube videos of this one, though, and Sidney Coleman was really a Feynman-class edutainer, perhaps as under-recognized as von Neumann is relative to say Everett on this topic :-) }. I should perhaps have used the word "entanglement" rather than "intrication". Oops.
      - cb321 4y ago
        Also of interest might be the treatment by Lev Landau in his Course on Theoretical Physics Volume 3: Quantum Mechanics - non-relativistic theory. Deriving the Born "postulate" is in Section7: "The wave function and measurements" in the most available 2nd edition (but it is admittedly a rather abbreviated derivation). I am not sure if that was in the original 1958 edition. Quantum systems measuring other quantum systems is part & parcel of quantum computation. So that can lead to more clear thinking on (some of) these matters.
rocqua 4y ago
Why would that force collapse? I would almost expect that the lack of communication over those distances forces _more_ uncertainty (i.e. a wider probability distribution) rather than less uncertainty.
- im3w1l 4y ago
  It's kind of a joke, which is what I meant by -of-the-gaps. If two particles are outside of each others event horizons, they can't communicate so you can't tell whether they are entangled (AA or BB) or whether the system has collapsed into say AA.
gus_massa 4y ago
If you have only one particle of the entangled pair, you can't do any experiment to check if they pair is still entangled or someone else has done something to the other particle and broke the entanglement. Someone else is not necessarily a person. May be a device or just a brick. In a common case, when you measure your particle you get 50% "yes" and 50% "no". So if you have a stream of particles that are one half of an entangled pair, you just get a random sequence. It doesn't matter if the other half is still flying happily in vacuum, got into a detector like the one you have, or it just hit a wall. You just get a random sequence. Otherwise, it could be used to build a FTL "walkie talkie". If you later can talk with someone in the other side that measured the other half of the pairs, then both of you can compare notes and notice that the two random sequences are equal or oposite or something in between according to which experiment each of you have done.
- im3w1l 4y ago
  Dang I low key have a problem here because I already mentioned it was a joke and gave the same explanation, but because this is the top reply and the comments both show n-hours ago it looks like I walked back my statement in response, and I think it's fair to say that this is why the original comment got a down vote and ended up at the bottom.
  - gus_massa 4y ago
    After reading your comment again, now I'm wondering how does the variation of QM discussed in the article handle the special cases you mentioned. In the usual QM the explanation is "easy" because the collapse is magical. But if they want to eliminate the magic and propose a underlying "physical" process for the collapse then they have nasty problems and FTL transmission.

by im3w1l 4y ago

In true collapse-of-the-gaps style, what if collapse happens when an entangled system becomes so large that the edges of it are outside of each others event horizons due to cosmic inflation?

bowsamic 4y ago

I think you mean expansion rather than inflation (inflation is something that happened very briefly at the beginning of the universe). In models with collapse, the collapse happens instantaneously, no matter what

cb321 4y ago
As with any unsettled questions there are pros & cons to the various takes on quantum reality. Part of the appeal of MWI (intrication of observer into observed system as part of the measurement process) to me was always that the instantaneousness you mention here is a very "ordinary" kind of "fastness by synchronization". It's basically just a kind of causal wavefront hitting. There are plenty of "infinitely fast" synchronization effects like this..some perhaps less obvious than others, but many pretty pedestrian and accessible to lay people. Neither the junction of a scissors or the "spot light" on clouds need be constrained by light speed, for example. People routinely abuse "nothing" (or maybe "go") in the " 'nothing' can 'go' faster than light" saying. :-)
- kgwgk 4y ago
  > intrication of observer into observed system as part of the measurement process That was already part of von Neumann’s model of measurement over 90 years ago.
  - cb321 4y ago
    Yeah. Perhaps most charmingly treated here: https://arxiv.org/abs/2011.12671 https://arxiv.org/abs/2011.12671 { EDIT: though surely many other places! There are also YouTube videos of this one, though, and Sidney Coleman was really a Feynman-class edutainer, perhaps as under-recognized as von Neumann is relative to say Everett on this topic :-) }. I should perhaps have used the word "entanglement" rather than "intrication". Oops.
    - cb321 4y ago
      Also of interest might be the treatment by Lev Landau in his Course on Theoretical Physics Volume 3: Quantum Mechanics - non-relativistic theory. Deriving the Born "postulate" is in Section7: "The wave function and measurements" in the most available 2nd edition (but it is admittedly a rather abbreviated derivation). I am not sure if that was in the original 1958 edition. Quantum systems measuring other quantum systems is part & parcel of quantum computation. So that can lead to more clear thinking on (some of) these matters.

rocqua 4y ago

Why would that force collapse? I would almost expect that the lack of communication over those distances forces _more_ uncertainty (i.e. a wider probability distribution) rather than less uncertainty.

im3w1l 4y ago
It's kind of a joke, which is what I meant by -of-the-gaps. If two particles are outside of each others event horizons, they can't communicate so you can't tell whether they are entangled (AA or BB) or whether the system has collapsed into say AA.

gus_massa 4y ago

If you have only one particle of the entangled pair, you can't do any experiment to check if they pair is still entangled or someone else has done something to the other particle and broke the entanglement. Someone else is not necessarily a person. May be a device or just a brick. In a common case, when you measure your particle you get 50% "yes" and 50% "no". So if you have a stream of particles that are one half of an entangled pair, you just get a random sequence. It doesn't matter if the other half is still flying happily in vacuum, got into a detector like the one you have, or it just hit a wall. You just get a random sequence. Otherwise, it could be used to build a FTL "walkie talkie". If you later can talk with someone in the other side that measured the other half of the pairs, then both of you can compare notes and notice that the two random sequences are equal or oposite or something in between according to which experiment each of you have done.

im3w1l 4y ago
Dang I low key have a problem here because I already mentioned it was a joke and gave the same explanation, but because this is the top reply and the comments both show n-hours ago it looks like I walked back my statement in response, and I think it's fair to say that this is why the original comment got a down vote and ended up at the bottom.
- gus_massa 4y ago
  After reading your comment again, now I'm wondering how does the variation of QM discussed in the article handle the special cases you mentioned. In the usual QM the explanation is "easy" because the collapse is magical. But if they want to eliminate the magic and propose a underlying "physical" process for the collapse then they have nasty problems and FTL transmission.