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Experiments spell doom for physical-collapse explanation of quantum weirdness

quantamagazine.org

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Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#121

Post by MockObject »

telmo wrote: post #52
wongarsu wrote: post #12

Earlier quoted context omitted.

To be fair, the Copenhagen interpretation doesn't really fit today's world view. We have largely moved away from viewing humans or "consciousness" as something special, so the notion that an observer collapses the wave function just seems weird now. "Many worlds" or "the wave function never collapses, you are in a superposition" both make much more sense with how we currently view the world

I also prefer the Many Worlds interpretation and I do think that it is gaining popularity in relation to Copenhagen, but I'm not sure what you mean by "today's world view". And who is this "we" that you write about? I prefer Many Worlds because it is a simpler explanation, so I follow Occam's razor. That's it. Consciousness and the existence of qualia remains a fundamental mystery. There is something definitely speci…

> I prefer Many Worlds because it is a simpler explanation, so I follow Occam's razor. That's it.

Zillions of new invisible universes being created every moment is the simplest explanation you found?

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#122

Post by tsimionescu »

telmo wrote: post #52
wongarsu wrote: post #12

Earlier quoted context omitted.

To be fair, the Copenhagen interpretation doesn't really fit today's world view. We have largely moved away from viewing humans or "consciousness" as something special, so the notion that an observer collapses the wave function just seems weird now. "Many worlds" or "the wave function never collapses, you are in a superposition" both make much more sense with how we currently view the world

I also prefer the Many Worlds interpretation and I do think that it is gaining popularity in relation to Copenhagen, but I'm not sure what you mean by "today's world view". And who is this "we" that you write about? I prefer Many Worlds because it is a simpler explanation, so I follow Occam's razor. That's it. Consciousness and the existence of qualia remains a fundamental mystery. There is something definitely speci…

MWI is exactly as simple mathematically as CI, so not sure what you mean by "simpler".

MWI still postulates the equivalent of wave function collapse, but instead of it happening only for the quantum system being measured, it is happening in the mind of the observer, as each "version" of that mind gets entangled with a single "version" of the outcome.

Even if you were to accept that this process is more natural (so not an "assumption") than wave-function collapse in principle, that simplicity completely falls apart when you then need to recover the relationship between the probability of observing a certain outcome and the amplitude of that outcome in the wave-function.

CI just says "when a quantum system described by a wave-function interacts with a measurement apparatus that measures in a certain basis, the wave-function gets updated to one of the values of its decomposition in that basis, with a probability equal to the modulus of the square root of its amplitude in that basis". Of course "measurement apparatus prepared in a certain basis" does a lot of work here, as we don't know how to define this in terms of a quantum system.

To make a similar quantitative prediction, MWI needs to define something like "the number of worlds", so that it can then say something like "when a quantum system interacts with a measurement apparatus prepared in a certain basis, the measurement apparatus becomes entangled with the quantum system such that for each value of that basis state there is a number of worlds proportional to the square root of the amplitude of each value of the decomposition in which the apparatus sees that particular value; if we were to compute the probability that we happen to live in a world where the apparatus is showing the value X, that probability would naturally be higher the more worlds there are where it shows this value X". So, the MWI has to actually introduce extra elements (the worlds and their number, and the observer wanting to compute a probability) to explain the actual measured results of quantum experiments.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#123

Post by im3w1l »

naasking wrote: post #87
im3w1l wrote: post #41

Earlier quoted context omitted.

We can detect their presence because they cause interference with our own.

Circular. You have to already accept many worlds to take this as evidence of worlds. You can argue for Many-Worlds on grounds of parsimony and clarity, but that's it.

No I don't think so. Many worlds is basically the hypothesis that we can put arbitrarily large systems in superposition. Like schroedingers cat that is both dead and alive, but instead it could be the whole lab, the whole planet, the whole galaxy that is simultaneously in two different states. We could test this by trying to actually do it, by putting really large and complex systems in superposition. If they both evolve as we'd predict and cause the interference patterns we predict, then we must conclude that these "other-labs", "other-planets", "other-galaxies", "other-worlds" evolve just like ours, and have a causal effect on ours.

Saying that sure, they evolve like ours, and sure they affect ours, but even so they are not real - that is I suppose one stance, but then you are getting pretty close to solipsism.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#124

Post by mjan22640 »

jfengel wrote: post #92
dzdt wrote: post #4

There is an often-repeated statement that different quantum mechanical theories are equivalent. This is an over-simplification. Is wave function collapse is a real thing or just an approximation of what happens when a large system is entangled? Some smart people have tried to make theories where wave function collapse is a real thing. These new experiments are working to rule out those ideas. My feeling is that Evere…

That's right: the "collapse" interpretation is an approximation. You can derive if from the MWI. We already know that the "worlds" separate and almost completely cease interacting. The interactions decrease to the order of "two to the power of Avogadro's number" almost immediately. The collapse interpretation rounds that to zero (at some arbitrary point). To make that more concrete you have to add a term to the equat…

Could the other branches be our dark matter?

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#125

Post by bnralt »

dzdt wrote: post #4

There is an often-repeated statement that different quantum mechanical theories are equivalent. This is an over-simplification. Is wave function collapse is a real thing or just an approximation of what happens when a large system is entangled? Some smart people have tried to make theories where wave function collapse is a real thing. These new experiments are working to rule out those ideas. My feeling is that Evere…

> There is an often-repeated statement that different quantum mechanical theories are equivalent.

Worse than that, I'd say that "physical collapse" is usually presented to the general public as established scientific fact, even by prominent scientists that know better.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#126

Post by HALtheWise »

abecedarius wrote: post #109
cbruns wrote: post #105

Earlier quoted context omitted.

Sounds like Three Body Problem. Not golden age though.

It's an Asimov story whose title I forget. The truth in question was a defense against nuclear bombs.

Breeds There a Man...?

https://en.wikipedia.org/wiki/Breeds_There_a_Man...%3F

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#127

Post by naasking »

im3w1l wrote: post #123
naasking wrote: post #87

Earlier quoted context omitted.

Circular. You have to already accept many worlds to take this as evidence of worlds. You can argue for Many-Worlds on grounds of parsimony and clarity, but that's it.

No I don't think so. Many worlds is basically the hypothesis that we can put arbitrarily large systems in superposition. Like schroedingers cat that is both dead and alive, but instead it could be the whole lab, the whole planet, the whole galaxy that is simultaneously in two different states. We could test this by trying to actually do it, by putting really large and complex systems in superposition. If they both ev…

> Saying that sure, they evolve like ours, and sure they effect ours, but even so they are not real - that is I suppose one stance, but then you are getting pretty close to solipsism.

No, you'd get something like Bohmian mechanics, or Rovelli's relational interpretation. Which is my point: you can only take this as evidence of other worlds if you basically smuggle those assumptions in.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#129

Post by kgwgk »

herdcall wrote: post #54
dzdt wrote: post #4

There is an often-repeated statement that different quantum mechanical theories are equivalent. This is an over-simplification. Is wave function collapse is a real thing or just an approximation of what happens when a large system is entangled? Some smart people have tried to make theories where wave function collapse is a real thing. These new experiments are working to rule out those ideas. My feeling is that Evere…

Check out "superdeterminism," first proposed by Bell (of Bell's inequality fame) himself and currently being vigorously pursued by Sabina Hossenfelder. There is no "collapse" per se according to this model and everything is really classical with hidden variables, and the entanglement comes because everything shared the same origin (the big bang). A very fascinating and in my opinion the best explanation, though it's…

> Check out "superdeterminism," first proposed by Bell (of Bell's inequality fame) himself

“Proposed” - but as something that avoids the issue but it’s not worthy of much consideration.

  - I was going to ask whether it is still possible to maintain, in the light of experimental experience, the idea of a deterministic universe?

  You know, one of the ways of understanding this business is to say that the world is super-deterministic. That not only is inanimate nature deterministic, but we, the experimenters who imagine we can choose to do one experiment rather than another, are also determined. If so, the difficulty which this experimental result creates disappears.

  - Free will is an illusion - that gets us out of the crisis, does it?

  That's correct. In the analysis it is assumed that free will is genuine, and as a result of that one finds that the intervention of the experimenter at one point has to have consequences at a remote point, in a way that influences restricted by the finite velocity of light would not permit. If the experimenter is not free to make this intervention, if that also is determined in advance, the difficulty disappears.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#130

Post by addaon »

HALtheWise wrote: post #126
abecedarius wrote: post #109

Earlier quoted context omitted.

It's an Asimov story whose title I forget. The truth in question was a defense against nuclear bombs.

Breeds There a Man...? https://en.wikipedia.org/wiki/Breeds_There_a_Man...%3F

That's it! Thanks!

Clearly left a mark on my memory.

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