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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

#151

Post by pred_ »

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…

> Is wave function collapse is a real thing or just an approximation of what happens when a large system is entangled?

I've listened to enough Carroll to convince myself that I think MWI makes sense, but what I never got is that it doesn't seem to offer much in terms of explanation of how the entangled state ends up being what it is: We see a particular result of an experiment with many possible a priori outcomes, but is there a mechanism that determines which particular entangled state we end up in? Something like the phases of the wave functions on individual Hilbert space sectors conspiring to produce a certain outcome, so that an omnipotent observer with full access to both parts would be able to tell what happens a priori, no dice being rolled? Or is that just hidden variable theory?

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

#152

Post by GoblinSlayer »

pdonis wrote: post #118
GoblinSlayer wrote: post #112

Earlier quoted context omitted.

>This is especially problematic because QM doesn't predict any particular decomposition of a quantum state into particular classical states. It does predict it, this decomposition is called decoherence, where a classical state splits into a superposition of several different classical states.

> this decomposition is called decoherence, where a classical state splits into a superposition of several different classical states. No, that's not what decoherence is. Decoherence is the spread of entanglement over a very large number of untrackable degrees of freedom (usually referred to as the "environment"). This makes interference effects unobservable. But decoherence itself does not involve any "splitting"; t…

AFAIK the largest molecule to show quantum behavior in experiments is somewhere at 100 atoms. I suppose that's all "environment" you need for a large number of degrees of freedom.

And yes, spread of entanglement does mean splitting. Entangled state is not factorizable, because all states in it are split. This splitting is the result of splitting of the initial state.

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

#153

Post by drewrv »

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…

I'm a fan of hers but I think many of her criticisms of string theory, multiverse stuff, etc, apply equally well to superdeterminisim.

That being said, in her latest book she has a pretty strong argument against free will that does not require superdeterminisim so if that sounds interesting check it out.

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

#154

Post by d_tr »

TheOtherHobbes wrote: post #96
fallingfrog wrote: post #90

Earlier quoted context omitted.

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?

It is the other way around. The "universes" are there when you solve the equations, and you can either let them be or keep only one by invoking the collapse.

The collapse amounts to just setting some terms to zero.

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

#156

Post by ffhhj »

AnIdiotOnTheNet wrote: post #77
herdcall wrote: post #54

Earlier quoted context omitted.

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…

Even without superdeterminism free will is a concept that only makes any sense in specific contexts. To say otherwise is to introduce God of the Gaps style woo.

Free will is about choosing what binds us, as we can't choose being free of matter without becoming inmaterial.

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

#157

Post by plutonorm »

jfengel wrote: post #144
mjan22640 wrote: post #124

Earlier quoted context omitted.

Could the other branches be our dark matter?

No. They don't behave at all like dark matter. Among other things, there's no reason for them to be distributed in a halo, nor for some galaxies to lack them.

Broad statements, do you have the time to elaborate?

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

#158

Post by ryeights »

pdonis wrote: post #119
TheOtherHobbes wrote: post #96

Earlier quoted context omitted.

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?

The MWI does not postulate extra universes, although that pop science description is unfortunately common even though it is wrong. The MWI just says that the one universe that exists is actually very, very different from what we perceive. (To be clear, I'm not saying this correct description makes the MWI any more palatable. I am just clarifying exactly what kind of unpalatableness the MWI requires.)

Can you elaborate on this? The Wikipedia page for MWI says

>The many-worlds interpretation implies that there are most likely an uncountably infinite number of universes.

https://en.wikipedia.org/wiki/Many-worlds_interpretation

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

#159

Post by sillysaurusx »

Replying to a now-deleted comment:

> Is there a good ... idiots guide to interpretation of quantum weirdness ? I am more than a little lost

I’ve got you covered. And believe it or not, you’ll be joining Tiktok University today:

https://www.tiktok.com/t/ZTRHqk6MP/

Tiktok has been quietly amassing a huge library of educational content, and I’ve been diligently sorting those into collections. I’ll post several more related to physics.

https://www.tiktok.com/t/ZTRHqLx2k/

https://www.tiktok.com/t/ZTRHqBn2L/

Why entangled electrons can’t communicate information: https://www.tiktok.com/t/ZTRHqBCLq/

Heisenberg uncertainty principle: https://www.tiktok.com/t/ZTRHq8XN3/

https://www.tiktok.com/t/ZTRHqY49j/

A more advanced one: https://www.tiktok.com/t/ZTRHq2pYS/

And a break from quantum weirdness, just ‘cause I like it: https://www.tiktok.com/t/ZTRHqBQHE

I have pages and pages of videos, so I probably shouldn’t spam them here. I can post more if there’s any interest.

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

#160

Post by naasking »

GoblinSlayer wrote: post #143
naasking wrote: post #106

Earlier quoted context omitted.

Yes, because it falsifies every interpretation of quantum mechanics not just MWI itself. I think in context here, "is superdeterminism falsifiable" is as silly a question as "is logic falsifiable" or "is causality falsifiable". Specific mmathematical, causal or superdeterministic models are always falsifiable, but the idea that superdeterminism as a whole is not falsifiable should be no more surprising or interesting…

If superdeterminism allows specific models. The idea is that the experimenter's behavior is fine tuned so he can't discover superdeterminism, which means falsification would be a paradox by definition.

Given we can enumerate all possible models because we can enumerate all possible Turing machines, we clearly have enough degrees of "freedom" in this universe that that isn't an issue.
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