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The Trouble with Quantum Mechanics

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Re: The Trouble with Quantum Mechanics

#101

Post by akvadrako »

lisper wrote: post #98
tigershark wrote: post #95

Earlier quoted context omitted.

If you are religiously convinced that the QIT interpretation is the only true one that doesn't make it true. For me it is just one of the many interpretations and I think that it is wrong on par with all the others that I'm aware of. If this wasn't the case then the measurement problem and the unification with the relativity theory (or with a theory that supersedes the relativity) would be already solved today. I'm r…

I am absolutely not religiously convinced that QIT is the only true explanation. In fact, I explicitly say at the end of my talk that it is not, that multiple-worlds is equally valid, and which you choose is a matter of personal preference. But if want to argue that no solution exists (and this is Weinberg's claim) then you have to consider all of the solutions on the table, and Weinberg does not. He deliberately ign…

> There are only people who are mystified because they are ignoring (or ignorant of) this crucial fact.

I don't think that's the only reason people are mystified. From what Weinberg says, and I've heard from other physicists, when you get to the root of the issue they just won't accept a multiverse theory.

It has profound philosophical consequences, so I guess they go looking for ways to make their understanding of QM fit their strongly held preconceptions. Some avoid this fact you just mentioned, but others fight the Born rule derivations or wrongly apply Occam's Razor or have more original objections.

Re: The Trouble with Quantum Mechanics

#102

Post by lisper »

akvadrako wrote: post #101
lisper wrote: post #98

Earlier quoted context omitted.

I am absolutely not religiously convinced that QIT is the only true explanation. In fact, I explicitly say at the end of my talk that it is not, that multiple-worlds is equally valid, and which you choose is a matter of personal preference. But if want to argue that no solution exists (and this is Weinberg's claim) then you have to consider all of the solutions on the table, and Weinberg does not. He deliberately ign…

> There are only people who are mystified because they are ignoring (or ignorant of) this crucial fact. I don't think that's the only reason people are mystified. From what Weinberg says, and I've heard from other physicists, when you get to the root of the issue they just won't accept a multiverse theory. It has profound philosophical consequences, so I guess they go looking for ways to make their understanding of Q…

> they just won't accept a multiverse theory

They don't have to. But they do have to accept that entanglement and measurement are the same physical phenomenon.

Re: The Trouble with Quantum Mechanics

#103

Post by akvadrako »

lisper wrote: post #102
akvadrako wrote: post #101

Earlier quoted context omitted.

> There are only people who are mystified because they are ignoring (or ignorant of) this crucial fact. I don't think that's the only reason people are mystified. From what Weinberg says, and I've heard from other physicists, when you get to the root of the issue they just won't accept a multiverse theory. It has profound philosophical consequences, so I guess they go looking for ways to make their understanding of Q…

> they just won't accept a multiverse theory They don't have to. But they do have to accept that entanglement and measurement are the same physical phenomenon.

These things are not unrelated :) If you accept that there is only the wave function as in the bare formalism, either an infinity of worlds or zero worlds, like in QIT, are the logical outcomes.

But I am not saying they "have to" - I'm saying that is their reason for not accepting the bare formalism.

Re: The Trouble with Quantum Mechanics

#104

Post by lisivka »

krastanov wrote: post #89
lisivka wrote: post #83

Earlier quoted context omitted.

I asking about outcome of Stern and Gerlach experiment. It's binary thing. Make public prediction, please.

Certainly, but then please first pose/define the question clearly. What do you call a macroscopic Stern-Gerlach experiment with balls floating on top of the waves of a fluid? It would be an amusing toy problem to work out if you define it for me. However, it does not change the main argument: there is nothing quantum in macroscopic experiments with water waves - interference does not imply "quantumness".

Lets define experiment as following (excuse me my bad English, please):

- vibrating bath with non-conductive, non-magnetic, non-paramagnetic, non-diamagnetic fluid;

- vibrating bath is wide enough to avoid excessive interference with reflected waves from bath sides;

- vibrating bath has regular pattern on top of fluid, without any irregularities in space of experiment;

- small charged droplets of fluid on top of bath;

- north and south poles of a magnet are placed horizontally, without touching of bath fluid or droplets, e.g. at sides of bath, OR over fluid, OR under bath;

- an apparatus creates droplets of same size with random spin in all 3 dimensions;

- droplets are forced to walk through the batch, starting at center line between north and south pole and following that line;

- without magnetic field applied, droplets must walk straight;

- an detectors to measure decline of droplet path from center line must be installed at end of magnetic pole.

I expect that, when magnetic field is applied, droplets will slide completely to left or completely to the right, like electrons in Stern-Gerlach experiment.

It's not a quantum experiment, of course, but it can provide insight on nature of quantum spin.

PS.

Sorry, droplets must be charged, not magnetic. Updated.

Re: The Trouble with Quantum Mechanics

#105

Post by lisivka »

gizmo686 wrote: post #87
lisivka wrote: post #85

Earlier quoted context omitted.

It's very unlikely. If Dave has Carol diary, then Carol made the trip already, so Carol will notice empty fuel tanks and big holes in the shield. She will may have problems with memory, but she is not stupid.

No she didn't. X is the point in spacetime where Carol begins her trip. From her perspective, Dave came from the future. The only reason that this cannot happen is that X and Y are so far away in space, and close in time, that it is impossible to travel between them.

Sorry, I cannot follow you here. Maybe it's well known thought experiment, but I'm unable to find it.

Re: The Trouble with Quantum Mechanics

#106

Post by krastanov »

lisivka wrote: post #104
krastanov wrote: post #89

Earlier quoted context omitted.

Certainly, but then please first pose/define the question clearly. What do you call a macroscopic Stern-Gerlach experiment with balls floating on top of the waves of a fluid? It would be an amusing toy problem to work out if you define it for me. However, it does not change the main argument: there is nothing quantum in macroscopic experiments with water waves - interference does not imply "quantumness".

Lets define experiment as following (excuse me my bad English, please): - vibrating bath with non-conductive, non-magnetic, non-paramagnetic, non-diamagnetic fluid; - vibrating bath is wide enough to avoid excessive interference with reflected waves from bath sides; - vibrating bath has regular pattern on top of fluid, without any irregularities in space of experiment; - small charged droplets of fluid on top of bath…

The main point of the Stern-Gerlach experiment was that the electrons hitting the screen were forming two distinct dots instead of a long spread out line, therefore proving that the angular momentum is quantised. In your example you will instead have simply a spread-out distribution because there is no quantisation of the angular momentum of your droplets.

The pilot wave usually refers to the spatial degrees of freedom, especially in these classical mock-ups with balls on top of waves. They do not properly addressed internal degrees of freedom like spin.

Unrelated to those macroscopic mock-ups, pilot wave theory actually has serious problems with the description of anything that is not a spatial degree of freedom.

You can still use pilot wave theory to describe the quantum behavior of the coordinates of a particle. But even then, the classical mock-ups we are discussing will not show anything inherently quantum - it will simply produce some interference patterns, that can be explained classically.

P.S. side note: An important part in the Stern-Gerlach experiment was that the magnetic field was not homogeneous, because it is the gradient of the field, not the field itself that causes the electrons to move.

Re: The Trouble with Quantum Mechanics

#107

Post by lisper »

akvadrako wrote: post #103
lisper wrote: post #102

Earlier quoted context omitted.

> they just won't accept a multiverse theory They don't have to. But they do have to accept that entanglement and measurement are the same physical phenomenon.

These things are not unrelated :) If you accept that there is only the wave function as in the bare formalism, either an infinity of worlds or zero worlds, like in QIT, are the logical outcomes. But I am not saying they "have to" - I'm saying that is their reason for not accepting the bare formalism.

> These things are not unrelated :) If you accept that there is only the wave function as in the bare formalism, either an infinity of worlds or zero worlds, like in QIT, are the logical outcomes.

Yep.

> But I am not saying they "have to" - I'm saying that is their reason for not accepting the bare formalism.

Well, OK, but then the burden is on them to come up with something better. QM is one of the most thoroughly tested scientific theories of all time. If you want to call yourself a scientist you can't legitimately reject it just because it doesn't make you feel warm and fuzzy inside.

Re: The Trouble with Quantum Mechanics

#108

Post by n4r9 »

lisper wrote: post #97
tim333 wrote: post #92

Earlier quoted context omitted.

I don't think that's been solved either or most physicists for that matter. I've read some of the attempts and they are not terrible good. I don't think Ron Garret even touched on the Born rule, Everett of many worlds just hand waves and assumes it. The attempts I've seen are basically of the form that if the rule was different from the probability equaling the absolute amplitude squared then reality wouldn't come ou…

FYI, I am Ron Garret. It's true that I don't talk about the Born rule or multiple worlds in the paper, but I do talk about multiple worlds in the video (at the end, during the Q&A) and in the blog posts I linked to above. As for the Born rule, what kind of an explanation are you hoping for? Some things can't be explained beyond, "That's just how it is." For example, why do the fundamental physical constants have the…

Two of the appealing arguments for many worlds type interpretations are that the number of required assumptions is small, and that it gives a reasonable physical intuition for why measurement outcomes occur as they do. Having to bolt on the Born rule weakens both of these.

In fact, I would even go so far as to say that if you are going to merely "enforce" the Born rule without justification, then you are no longer proposing an Everettian interpretation. The whole point of these interpretations is that simply "unitary quantum mechanics" describes the whole universe.

Re: The Trouble with Quantum Mechanics

#109

Post by n4r9 »

akvadrako wrote: post #96
tim333 wrote: post #72

Earlier quoted context omitted.

Indeed it's not that solved. A big problem is as Weinberg puts it >Several attempts following the realist approach have come close to deducing rules like the Born rule that we know work well experimentally, but I think without final success. which is kind of the heart of things.

I know of 3 modern ways to derive the Born rule for WMI and all have various reasonable (yet not airtight) assumptions. In physics you can never really prove anything, but there is no serious technical issues here. Actually probability (the Born rule) is much better defined in WMI then in any other interpretation or even classically. A related beautiful thing about WMI is that is creates genuine subjective probabilit…

Have you aware of Adrian Kent's critiques of (many of) these attempts?

https://arxiv.org/abs/0905.0624

Re: The Trouble with Quantum Mechanics

#110

Post by akvadrako »

lisper wrote: post #107
akvadrako wrote: post #103

Earlier quoted context omitted.

These things are not unrelated :) If you accept that there is only the wave function as in the bare formalism, either an infinity of worlds or zero worlds, like in QIT, are the logical outcomes. But I am not saying they "have to" - I'm saying that is their reason for not accepting the bare formalism.

> These things are not unrelated :) If you accept that there is only the wave function as in the bare formalism, either an infinity of worlds or zero worlds, like in QIT, are the logical outcomes. Yep. > But I am not saying they "have to" - I'm saying that is their reason for not accepting the bare formalism. Well, OK, but then the burden is on them to come up with something better. QM is one of the most thoroughly t…

Maybe I agree with you, but science is built on philosophy, which is not rigorous - but based on fuzzy feelings of what is right.

The fact that we accept QM because it predicts the outcome of experiments is philosophy. So I could theoretically imagine someone holding the belief in our universe being what it seems higher than mathematical sense.

Yet my primary point is physicists are just human and have all the same irrational tendencies as the rest of us. You can't ignore their feelings if you hope to convince them of something.

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