Experiments spell doom for physical-collapse explanation of quantum weirdness • Hacker News Board

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

#241

Post by thrown_22 » Sat, Oct 22, 2022, 1:08 AM UTC

masteranza wrote: post #226

thrown_22 wrote: post #225

Earlier quoted context omitted.

>Until you say a reasonable number of particles that make up the measuring apparatus where we should see _something_ weird starting to happen theoretically you're not even wrong.

Just saying something twice doesn't make it true. The "weird" thing you were perhaps referring too starts at very beginning of quantum mechanics framework. The Born rule is just a "conversion" of predictions of quantum framework to our classical language. The only option you have is to reject quantum mechanics as a whole and not try to patch it - because this clearly will not work.

The weird thing would be discontinuities showing up in wave function evolution without putting them there with the potential energy functions. In the few cases where we can get analytical solutions there are no discontinuities that look anything like wave function collapse.

You're whole thesis rests on the fact that this should fall out when we put 6e23 particles together for reasons.

So far we've not managed to simulate 1,000 quantum particles because the curse of dimensionallity means we run out of computers on earth rather quickly. Which makes anything you're saying pointless since we can't ever check it, even if we turned the whole observable universe into a computer.

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

#242

Post by ummonk » Sat, Oct 22, 2022, 1:08 AM UTC

whimsicalism wrote: post #138

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…

> though it's extremely controversial and taboo because of its implications on free will Uhh, no. Essentially all existing physical theories are devastating for any non-compatabilist account of free will.

Exactly. Even if you dispense with hard determinism and allow randomness in your theory, pure randomness is not really free will.

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

#243

Post by thrown_22 » Sat, Oct 22, 2022, 1:08 AM UTC

omnicognate wrote: post #229

thrown_22 wrote: post #222

Earlier quoted context omitted.

No one apart from Penrose took it seriously. You might as well say that Russell's Teapot is falsifiable because you only need to look through a finite amount of space to prove it's not there.

The theory made predictions that could be - and have been (read the article) - shown false. Do you have some other definition of falsifiability?

If you read the article there is still plenty of room for those effects to hide in, just like there was before these experiments were done. No one has changed their minds because of this.

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

#244

Post by ummonk » Sat, Oct 22, 2022, 1:15 AM UTC

naasking wrote: post #83

sebastialonso wrote: post #65

Earlier quoted context omitted.

Is superdeterminism even falsifiable?

Is Many-Worlds even falsifiable?

Yes. You could, for example, allow a measured particle to interact with an isolated measuring apparatus of varying size - from a few atoms to a macroscopic object - and see how the size affects the system - so you get evidence of decoherence?

Also, many worlds interpretation as it currently exists is already falsified by its incompatibility with gravitational nonlinearity.

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

#245

Post by jamiek88 » Sat, Oct 22, 2022, 1:17 AM UTC

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…

> two to the power of Avogadro's number"

So you’re saying… theres a chance…? :)

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

#246

Post by throwaway81523 » Sat, Oct 22, 2022, 1:23 AM UTC

sebastialonso wrote: post #65

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…

Is superdeterminism even falsifiable?

't Hooft's version of superdeterminism, according to his book, can be falsified by demonstrating a large scale quantum computer. I don't know if Hossenfelder's version is something different or how she would account for this.

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

#247

Post by ummonk » Sat, Oct 22, 2022, 1:26 AM UTC

tshaddox wrote: post #148

naasking wrote: post #89

Earlier quoted context omitted.

I'm skeptical that Deutsch actually meant that, but even smart people have crazy ideas.

He wrote a pretty well known article about it that as far as I can tell wasn’t written off-hand and hasn’t been retracted or disavowed. I’m pretty confident he meant it.

There has to be some misinterpretation going on here (or David Deutsch just hasn't thought this through). You can have a quantum computer in a superposition of states, but that isn't many worlds; to have many worlds, the computer has to interact with the outside world and split the outside world into a corresponding superposition of states. Such interaction with the outside world prevents a quantum computer from functioning - and it's precisely such information leakage to the outside world that is a major difficulty when trying to scale up quantum computers.

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

#248

Post by ummonk » Sat, Oct 22, 2022, 1:29 AM UTC

GoblinSlayer wrote: post #100

naasking wrote: post #83

Earlier quoted context omitted.

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.

There is non-linearity in the evolution operator though - it's called gravity. It's why MWI in its trivial form is falsified - though with a linear theory of everything (potentially string theory) - it might be possible.

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

#249

Post by throwaway81523 » Sat, Oct 22, 2022, 1:33 AM UTC

c1ccccc1 wrote: post #212

lamontcg wrote: post #184

Earlier quoted context omitted.

> which theories are highly speculative. So QM itself is on very, very solid ground. You're using it now on your computer. The interpretations of QM and the attempts to reconcile the exceptionally well tested mathematics of QM and the reality that we experience which is not-QM at all are all philosophical with zero evidence. Everyone just tries to make compelling arguments based on things like Occam's razor about why…

Many worlds is absolutely testable, since if we observe collapse in even a single one of these experiments then that completely falsifies many worlds. If one of these experiments discussed in the article had actually observed a collapse, then I have no doubt we'd be seeing headlines like "many worlds theory disproven", and Nobel prizes for the physicists involved. It would be the biggest discovery in physics for deca…

We "observe" collapse all the time, and can calculate the probabilities of the different possible collapsed states of a not-yet-observed superposed or entangled state using the Born rule. What we don't know, and can't tell, is whether we have seen an "objective collapse" (we live in just one universe, that undergoes a discontinuous change at the time of measurement) or in something like MWI. That is question for philosophers afaik. The experiment in the title falsifies certain models of objective collapse, but others are harder to falsify.

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

#250

Post by ravi-delia » Sat, Oct 22, 2022, 2:37 AM UTC

nil-sec wrote: post #79

ravi-delia wrote: post #47

Earlier quoted context omitted.

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…

It’s quite nice to have something irreversible though. It gives you time. Also nobody really thinks QM is the end of it, assuming semi classical physics under the hood is just odd to me. There is something below QM that we don’t understand yet (AdS/CFT looks like a good start to me) and personally I think the whole interpretation of QM debate will look stupid in retrospect. Yeah collapse is odd, but it just shows us…

You get time from all sorts of technically reversible things though! Even in a totally classical universe entropy gives us an arrow of time. Under MWI decoherence is reversible, but is functionally irreversible in the same way entropy is.

You're right though, I very much doubt QFT as it stands is the bottom. However, that doesn't mean the current debate is stupid. Whatever underlies QM, you'd still expect the measurement effect to also be an emergent property. The debate about whether atoms existed is still meaningful even though we now know that "atom" isn't a perfectly natural category. Indeed there are protons and such underling the physics, but the protons do pretend to be atoms much of the time, and thus pretend to do all the things we use atoms to predict.

Similarly, MWI and collapse (as well as, if less so, weirder theories) can be good explanations as to why a quantum phenomenon occurs even if there's also a reason they happen.