An explanation of the 'Many Interacting Worlds' theory of quantum mechanics (by Sean Carroll and Chip Sebens)
post by Ander · 2014-12-18T23:36:48.683Z · LW · GW · Legacy · 7 commentsThis is the first explanation of a 'many worlds' theory of quantum mechanics that has ever made sense to me. The animations are excellent:
http://www.preposterousuniverse.com/blog/2014/12/16/guest-post-chip-sebens-on-the-many-interacting-worlds-approach-to-quantum-mechanics/
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comment by shminux · 2014-12-19T03:26:14.054Z · LW(p) · GW(p)
The animations are pretty, but the article is short on actual explanations. How does adding a detector to one of the slits kill the interference pattern? How exactly do the particles interact in the configuration space? How does entanglement arise in this picture? Hopefully these issues are addressed in the actual paper, though it's not at all obvious from the abstract.
Replies from: Ander, None↑ comment by [deleted] · 2014-12-20T09:00:00.301Z · LW(p) · GW(p)
Presumably, if you put a detector in front of one of those slits, the particles cannot pass through both slits, and thus you wouldn't have those two moving collections of particles. You would have one moving collection, which would simply fan out without interference.
Replies from: shminux↑ comment by shminux · 2014-12-20T17:28:53.110Z · LW(p) · GW(p)
Surely in some worlds you detect a particle and in others you don't, so there are plenty of particles going through each slit on aggregate.
Replies from: None↑ comment by [deleted] · 2014-12-20T21:18:48.268Z · LW(p) · GW(p)
Right. But I think the idea is there are two groups of particles when both slits are open. When one is blocked a particle detector, they can't go through both slits.
With a detector in one of the slits, you will only see one group, not the unmeasured state with both groups.
Replies from: shminux↑ comment by shminux · 2014-12-21T17:05:12.272Z · LW(p) · GW(p)
That's not how the double-slit experiment works. Both slits remain open at all times. The detector only detects the passage of the particle through one of the slits.
Replies from: None↑ comment by [deleted] · 2014-12-21T17:57:06.238Z · LW(p) · GW(p)
Right.
I'm not saying I'm an expert, or even that I'm remotely intriguied by Interacting Many Worlds.
My point is, as long as the photon(s) have been undetected, they can travel through both slits.
As soon as you detect the photon at one of the slits, it cannot, as it has been measured at one of the slits.