What do you think of the alternate interpretations of QM?

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  • #1
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The standard interpretation of QM advocates that there are no "hidden variables", and that the universe is not deterministic. Sure, maybe Bell's work supports that view, but there exist some deterministic theories of quantum mechanics (like the De Broglie-Bohm theory) or other stuff, like the many worlds interpretation, that are consistent with that. What is your personal opinion on such theories?
 

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  • #2
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It's not clear to me that there is a "standard" interpretation of QM - if there were such a thing, then we wouldn't have so many endless and inconclusive threads on interpretation. (Search for these threads and read them - there's been a lot said on the topic already).

You are also somewhat misstating the conclusion of Bell's work. It doesn't show that there are no hidden variables, or that the universe is necessarily non-deterministic; it excludes those hidden variable theories that have particular characteristics. It's interesting because these characteristics ("locality" and "realism") are required of any theory that matches our classical intuition of how things work; so in effect it says that we must abandon this classical "common-sense" view of the world.

All interpretations predict the same experimental results so there is no way of objectively determining which one is "right". You are free to choose whichever interpretation you are most comfortable with, or even to choose one or another according to whatever makes it easiest to reason about the problem you're working on right now. On the one hand, de gustibus non est disputandum, and on the other hand for many people such matters are the only things worth arguing about.
 
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  • #3
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You are also somewhat misstating the conclusion of Bell's work. It doesn't show that there are no hidden variables, or that the universe is necessarily non-deterministic; it excludes those hidden variable theories that have particular characteristics.
Sure. That's why I said that some hidden variable theories are consistent with it.

It's not clear to me that there is a "standard" interpretation of QM
The Copenhagen interpretation is frequently considered the "standard" interpretation. By "alternate" I mostly meant hidden variable interpretations.
 
  • #4
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My opinion is I find it more interesting to get the right answer than to ponder what it all means.
 
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For me, the biggest problem with Copenhagen is that it artificially bifurcates the world into two incommensurable realms: one for which the formalism of Hilbert spaces, etc., can be applied, and one for which it can’t. What results is an odd, dualistic ontology that is deeply anti-physics, at least in my estimation. The obvious remedy is to apply QM’s formalism to all systems, including the measurement apparatus, the observer, and the ambient environment. What I’m describing, of course, is the Everettian approach. The question then becomes if such a universal, disciplined application of QM’s formalism can somehow reproduce the world of common experience. Based on my understanding of the mechanism of decoherence, I think it can.
 
  • #6
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My opinion is I find it more interesting to get the right answer than to ponder what it all means.
That's a good opinion, but I know it doesn't satisfy some people.
 
  • #7
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What I’m describing, of course, is the Everettian approach.
That approach is very popular from what I have observed, but isn't it a bit... I think the best way to describe it is ad hoc? Don't get me wrong, it intuitively makes more sense, but while the Copenhagen interpretation is more general and does not attempt to explain anything at a deeper level, the many worlds interpretation introduces literal new worlds completely out of the blue! I feel a bit uncomfortable with the way it is hypothesized.
 
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That approach is very popular from what I have observed, but isn't it a bit... I think the best way to describe it is ad hoc? Don't get me wrong, it intuitively makes more sense, but while the Copenhagen interpretation is more general and does not attempt to explain anything at a deeper level, the many worlds interpretation introduces literal new worlds completely out of the blue! I feel a bit uncomfortable with the way it is hypothesized.
Nowadays, most Everettians view the so-called 'many worlds' as a consequence of unitary evolution and decoherence, rather than an a priori input to the theory.
 
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  • #9
Demystifier
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The standard interpretation of QM advocates that there are no "hidden variables", and that the universe is not deterministic. Sure, maybe Bell's work supports that view, but there exist some deterministic theories of quantum mechanics (like the De Broglie-Bohm theory) or other stuff, like the many worlds interpretation, that are consistent with that. What is your personal opinion on such theories?
I think it is always illuminating to think of different interpretations of the same observed facts.

Concerning QM, I like the analogy with magic tricks:
https://www.physicsforums.com/threa...-bohmian-mechanics.898028/page-5#post-5652596
 
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  • #10
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I think the importance of different interpretations is twofold:

1. Pick an aspect of QM you do not like and we have an interpretation that gets rid of it - but not all at once. Note - what one likes or not likes is very personal and beyond science. Its very wise to always keep this in mind when discussing interpretations.

2. It sheds light on what the formalism says. For example it may seem the formalism is inherently probabilistic, but since we have interpretations where it isn't that's wrong. Similarly for collapse. Once you realize this some of the discussions about the foundations of QM especially in popularizations, beginner texts and the writings of the early pioneers; some love to quote; is well almost laughable. It really allows you to cut through BS.

Thanks
Bill
 
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  • #11
Paul Colby
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Classical mechanics is simply a set of rules that provides reliable predictions and models of various phenomena. People claim they understand it which I argue really means they feel "comfortable" with the rules of classical mechanics. Same is true for QM, just different rules which applies to energy and size scales we don't live in. And, of course, no one will allow you to claim to be comfortable QM rules either.
 
  • #12
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My last post was removed, because it didn't meet the required standards of a reference. Here it is:

"So you think it really doesn't matter at all? Well, maybe now it doesn't, but I remember reading something about some physician proposing an experiment involving some macroscopic quantum eraser that could provide evidence supporting an interpretation over the others."

Well, I looked it up. There was a 1986 paper by David Deutsch titled 'Three experimental implications of the Everett interpretation' that proposed some ways to test the MWI. There's also this very interesting entry: https://plato.stanford.edu/entries/qm-manyworlds/ (read number 5). From what I have understood so far, Deutsch's proposed experiments essentially require using cats (well, not cats, macroscopic objects you get the idea) in the place of electrons and other tiny particles for usual quantum erasure/interference experiments

There's a very disappointing quote from that source: "These proposals are all for gedanken experiments that cannot be performed with current or any foreseeable future technology."

I think stuff gets less scientific and more philosophical beyond this point.
 
  • #13
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From what I have understood so far, Deutsch's proposed experiments essentially require using cats (well, not cats, macroscopic objects you get the idea) in the place of electrons and other tiny particles for usual quantum erasure/interference experiments
Well since the modern version of MW is the same as decoherent histories except the histories all occur instead of just one that seems very very unlikely - in fact I would say impossible.

All these various interpretations were deliberately cooked to have the usual QM formalism. All you would end up doing is confirming that formalism because of the way they were developed.

A while ago some people though they could tell BM from regular QM and even did some experiments
https://arxiv.org/abs/quant-ph/0206196

This caused quite a stir but sounder reasoning prevailed and the flaw discovered (it had something to do with an incorrect use of the Dirac Delta function if I remember correctly) - as it must be for the reason I cited above.

Thanks
Bill
 
  • #14
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Well since the modern version of MW is the same as decoherent histories except the histories all occur instead of just one that seems very very unlikely - in fact I would say impossible.

All these various interpretations were deliberately cooked to have the usual QM formalism. All you would end up doing is confirming that formalism because of the way they were developed.

A while ago some people though they could tell BM from regular QM and even did some experiments
https://arxiv.org/abs/quant-ph/0206196

This caused quite a stir but sounder reasoning prevailed and the flaw discovered (it had something to do with an incorrect use of the Dirac Delta function if I remember correctly) - as it must be for the reason I cited above.

Thanks
Bill
Yes, but either one or the other interpretations must be correct, they can't all be correct at once, so there must be something to distinguish them.
 
  • #15
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Different interpretations can all be correct even if they contradict. There is no right or wrong interpretation.
 
  • #16
Paul Colby
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Yes, but either one or the other interpretations must be correct, they can't all be correct at once, so there must be something to distinguish them.
If this were true, they wouldn't be interpretations they would be distinct theories. My understanding they are the same theory with different words sprinkled on top.
 
  • #17
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Yes, but either one or the other interpretations must be correct, they can't all be correct at once, so there must be something to distinguish them.
That is fallacious reasoning.

For example it is well known there is no way to tell the difference between LET and standard SR, so much so many physicists would call them the same theory.

In order to prove your assertion you must figure out a way to do it. Some claim to have done so but they have not stood up.

Thanks
Bill
 
  • #18
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That is fallacious reasoning.

For example it is well known there is no way to tell the difference between LET and standard SR, so much so many physicists would call them the same theory.

In order to prove your assertion you must figure out a way to do it. Some claim to have done so but they have not stood up.

Thanks
Bill
What does LET stand for?

From my understanding, all the different interpretations produce the same observations when it comes to wavefunctions etc., but there are differences between them. If you can't possibly distinguish between them, it's not scientific. I might as well say that a flying spaghetti monster comes in and solves everything.
 
  • #19
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  • #20
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I might as well say that a flying spaghetti monster comes in and solves everything.
That's the FSM interpretation. No one uses it because it doesn't seem to make any problems easier to reason about (unlike, for example, collapse interpretations which many people find helpful in talking about many problems) and just about everyone finds it ugly and absurd. But this is just reinforcing the point I tried to make in the last paragraph of post #2 in this thread: interpretations are chosen on the basis of utility and aesthetic appeal to the interpretation-holder.
 
  • #21
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just about everyone finds it ugly and absurd
Come on, don't be so harsh to FSM, it's not ugly, it's... different... :biggrin:

So what you're saying is that the different interpretations have nothing to do with proposing a model for what might really be happening, but instead have to do more with what you like more and is more convenient to you. For example, the MWI does not claim that there ACTUALLY are different universes, but that it's convenient to imagine there are different universes. Is this it?
 
  • #22
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I simply don't try to interpret it. I have the equations and they work, why should I care how? I'm not in a position to advance the field any, so I don't bother trying to figure out what's going on. To me, as long as it's logically consistent and doesn't violate any experimental data, all interpretations are equally valid.

I think hidden variables is not one of them, aren't there experiments to show that a hidden variable couldn't possibly create the behavior we see?

Personally, it's my hunch that the universe is deterministic and we're still at too high of a level to figure out how. Some day we'll have a theory that can predict events at Plank scales. But that's just a hunch, I have no reason to believe that over anything else.
 
  • #23
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the different interpretations have nothing to do with proposing a model for what might really be happening
That depends on what you think "proposing a model" means. If it means "using exactly the same math and making exactly the same predictions, but using different ordinary language verbiage to describe what's going on", then different interpretations do propose different models. But I think it's more usual to interpret "proposing a model", at least in physics, to include making at least some predictions that are different from other models. None of the QM interpretations do that; they all make exactly the same predictions.
 
  • #24
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aren't there experiments to show that a hidden variable couldn't possibly create the behavior we see?
There are experiments that show that the Bell inequalities are violated, and Bell's Theorem shows that a particular kind of hidden variable model (a "local realistic" one is the usual term, but IMO it's better to characterize the model by its mathematical properties) must satisfy the inequalities, so that kind of model is ruled out.
 
  • #25
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If it means "using exactly the same math and making exactly the same predictions, but using different ordinary language verbiage to describe what's going on",
I wouldn't call proposing the existence of multiple "worlds" "using different ordinary language verbiage". The ontological differences proposed by the various interpretations seem major to me, but I might be misunderstanding something.
 

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