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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

#91

Post by kgwgk »

cb321 wrote: post #49
bowsamic wrote: post #8

Earlier quoted context omitted.

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

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" sy…

> 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.

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

#92

Post by jfengel »

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 equations, making it theoretically testable, but it's remarkable that anybody could manage to test it in practice. It's clever to use a neutrino detector -- something designed to measure ludicrously small amounts of interactions.

I don't think anybody is surprised by the results, just that they could get any. The un-physical arbitrariness of the cutoff caused problems from the get-go.

I was going to say that it doesn't make MWI any more palatable, though I suppose it does. They've detected the other branches, albeit in a very indirect way. They're real. But they're just as inaccessible as they ever were.

You still need the concept of decoherence to make it work. The unstable equilibrium can't hold for large objects. That's both mathematically and physically sound.

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

#93

Post by xwolfi »

tshaddox wrote: post #88
naasking wrote: post #83

Earlier quoted context omitted.

Is Many-Worlds even falsifiable?

David Deutsch seems to think that a general intelligence running on a quantum computer ought to be able to observe itself existing in parallel worlds if many-worlds is true.

Which sadly means nothing, so many details being hidden behind the words "general", "intelligence", "running", "quantum computer", "ought", "oberve" and "existing".

If you could refine what these words all mean, I guess we could understand it as something more than "Deutsch seems to think that yes", which can replace your sentence entirely, "yes" describing it all as precisely.

I am myself, in some ways, a general intelligence running on a quantum computer but I dont feel like I can observe myself existing in a novel special way. Let alone being able to then express it for you in a way that is novel as well.

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

#94

Post by TheOtherHobbes »

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…

I don't see how relabelling "collapse" to "separation" and adding more or less infinitely proliferating universes solves the problem.

MWI also contradicts itself. Supposedly the universes are independent, but if their influence doesn't define the wave equation they do nothing to help explain it.

It's a very strong and exceptional claim with absolutely no evidence to support it. "Feeling" isn't enough.

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

#95

Post by jobs_throwaway »

ravi-delia wrote: post #47
rubidium wrote: post #35

Earlier quoted context omitted.

Many worlds is just some peoples favorite because they get too weirded out but indeterminism. They prefer a billiard ball universe and so invented the hairbrained many worlds theory.

Or- and hear me out with this one- they prefer an explanation which follows naturally from existing experiments and doesn't require a hacked together non-linear irreversible operation which occurs only under bizarre conditions exactly when needed to patch over experimental results. No one in the whole world cares if the universe is deterministic or not, but collapse is embedded in an entirely deterministic system. MW…

> No one in the whole world cares if the universe is deterministic or not

lol

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

#96

Post by TheOtherHobbes »

fallingfrog wrote: post #90
lupire wrote: post #9

Earlier quoted context omitted.

Disproving some form of measurable wave function does not provide evidence for MWI, which is unmeasurable and untestable nearly by definition.

Well, the thing is that the MWI is actually simpler than all the other interpretations, because it simply removes the idea of wave function collapse entirely. Any theory involving wave function collapse is adding something extra to quantum physics that can't be demonstrated experimentally. Because we live in the macro world, it feels like a single unitary reality is simpler, but actually, the MWI makes fewer assumpti…

You don't think postulating an unknown number of extra universes with a very poorly defined relationship with each other qualifies as an extra assumption?

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

#97

Post by ffhhj »

tshaddox wrote: post #88
naasking wrote: post #83

Earlier quoted context omitted.

Is Many-Worlds even falsifiable?

David Deutsch seems to think that a general intelligence running on a quantum computer ought to be able to observe itself existing in parallel worlds if many-worlds is true.

> observe itself existing in parallel worlds if many-worlds is true

If many-worlds is true, we are already observing ourselves in each of those universes in which we can observe, we just don't communicate with our replicas. And if the AGI can communicate with its other instances, the exponential replicas will quickly overload their channel.

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

#98

Post by tsimionescu »

ravi-delia wrote: post #47
rubidium wrote: post #35

Earlier quoted context omitted.

Many worlds is just some peoples favorite because they get too weirded out but indeterminism. They prefer a billiard ball universe and so invented the hairbrained many worlds theory.

Or- and hear me out with this one- they prefer an explanation which follows naturally from existing experiments and doesn't require a hacked together non-linear irreversible operation which occurs only under bizarre conditions exactly when needed to patch over experimental results. No one in the whole world cares if the universe is deterministic or not, but collapse is embedded in an entirely deterministic system. MW…

Actually, if you eliminate collapse entirely as a non-linear operation, then you have a new huge problem for QM: there is plenty of non-linearity in the universe (e.g. double pendulum experiments, not to mention GR), and QM predicts that there shouldn't be any non-linearity at all, if you eliminate wave function collapse/the Born postulate.

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

#99

Post by Comevius »

snowwrestler wrote: post #28
Comevius wrote: post #21

Earlier quoted context omitted.

No interpretation of quantum physics proposed by scientists ever required a conscious observer, that's more of a misinterpretation of what an observer is. It's an interaction, not a person or animal. As for the theory of consciousness, of course we are not special, it's information-processing, and it looks like thermodynamics is responsible for the emergence of information-processing structures. https://arxiv.org/abs…

A mental trick that helped me understand the concept of “an observer” in particle physics is to imagine it like playing billiards in a pitch black room. In normal human-scale billiards, there are immense numbers of photons flying around bouncing off everything. The photon interactions are far too small to affect the path of a moving billiard ball, but we can detect them easily with our eyes. So we can use photons to…

This is a great analogy, but also in experiments the presence or absence of the measuring device like a beamsplitter determines the outcome. The measuring device, the which-way detector is the observer, and it can be regarded as a quantum mechanical system. It's correlations with the rest of the system causes the particle behavior.

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

#100

Post by GoblinSlayer »

naasking wrote: post #83
sebastialonso wrote: post #65

Earlier quoted context omitted.

Is superdeterminism even falsifiable?

Is Many-Worlds even falsifiable?

Discovery of non-linearity in the evolution operator would falsify MWI. Like e.g. this germanium experiment gave a positive result.
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