Which Quantum Interpretation could make a difference?

[Gerenuk]

Is there an interpretation of quantum mechanics, which could make a difference to future calculations and results? Maybe an interpretation which could rewrite and simplify the algebra? Or one which has new testible results which when correct would change the quantum mechanical equations to make them more precise or simpler?

I mean there are popular interpretations like many world interpretation, but it is hard to see why one should put up a theory like this which is neither more powerful nor more intuitive than a copenhagen interpretation. Also Bohm might be easy to grasp for the human mind, but result-wise it only complicates things?

 

[StevieTNZ]

If you look at the thought experiment in GianCarlo Ghirardi's book 'Sneaking a Look at God's Cards', one could see if the Copenhagen interpretation holds or not.

 

[aimforclarity]

i think the GRW theory (ad hoc 'collapse' theory, which puts in collapse 'by hand' by adding a nonlinear term to the Sch Eq. ) gives testable results, since in reality no wavefunction collapses instantaneously. (see https://www.physicsforums.com/showthread.php?t=446783)
But i should warn you, i am no expert.
From what i understand, TI and PTI Transactional*Interpretation (John Cramer's) do not give new testable predictions.

 

[bohm2]

I think many of them claim that they make somewhat different predictions but only under as yet untestable situations. Consider one deBroglie/Bohm interpretation:

Should inflation be very firmly established, and should it be found that the predictions of quantum theory continue to hold well at all accessible lengthscales during the inflationary era, then this would constitute considerable evidence against the hypothesis of quantum nonequilibrium at the big bang (though of course, nonequilibrium from an earlier era might simply have not survived into the inflationary phase). Furthermore, it would rather undermine the view that quantum theory is merely an effective description of an equilibrium state. In principle, one could still believe that hidden variables exist, and that the hidden variables distribution is restricted to quantum equilibrium even at the shortest distances and earliest times. But in the complete absence of nonequilibrium, the detailed behaviour of the hidden variables (such as the precise form of the trajectories in de Broglie-Bohm theory) would be forever untestable. While exact equilibrium always and everywhere may constitute a logically possible world, from a general scientific point of view it seems unacceptable, and the complete ruling out of quantum nonequilibrium by experiment would suggest that hidden-variables theories should be abandoned.

Inflationary Cosmology as a Probe of Primordial Quantum Mechanics
http://lanl.arxiv.org/PS_cache/arxiv/pdf/0805/0805.0163v2.pdf

De Broglie-Bohm Prediction of Quantum Violations for Cosmological Super-Hubble Modes
http://lanl.arxiv.org/PS_cache/arxiv/pdf/0804/0804.4656v1.pdf

 

[aimforclarity]

If you are really interested in the subject i just found a great review article on decoherence and interpretations:

Decoherence, the measurement problem, and interpretations of quantum mechanics
Rev. Mod. Phys. 76, 1267–1305 (2005)
http://rmp.aps.org/abstract/RMP/v76/i4/p1267_1

 

[nonequilibrium]

Also Bohm might be easy to grasp for the human mind, but result-wise it only complicates things?

Why would you say that it complicates things result-wise?

 

[StevieTNZ]

The thought experiment in the book I mentioned is in regards to standard QM, not his GRW theory.

 

[StevieTNZ]

i think the GRW theory (ad hoc 'collapse' theory, which puts in collapse 'by hand' by adding a nonlinear term to the Sch Eq. ) gives testable results, since in reality no wavefunction collapses instantaneously. (see https://www.physicsforums.com/showthread.php?t=446783)
But i should warn you, i am no expert.
From what i understand, TI and PTI Transactional*Interpretation (John Cramer's) do not give new testable predictions.

GRW isn't exactly an interpretation of QM. its a completely new theory.

 

[aimforclarity]

GRW isn't exactly an interpretation of QM. its a completely new theory.

ok that is more strictly true since it modifies the SHE. but it also sheds some light on measrument and decoherence treating them as wavfunciton leaking from system with small #dof to a system with large #dof again see the post by zpower

 

[Gerenuk]

i think the GRW theory (ad hoc 'collapse' theory, which puts in collapse 'by hand' by adding a nonlinear term to the Sch Eq. ) gives testable results, since in reality no wavefunction collapses instantaneously. (see https://www.physicsforums.com/showthread.php?t=446783)
But i should warn you, i am no expert.
From what i understand, TI and PTI Transactional*Interpretation (John Cramer's) do not give new testable predictions.

Thanks! That's exactly the type of answer I'm looking for :)
And of course I'll try to understand it myself before I make a judgement.

If you are really interested in the subject i just found a great review article on decoherence and interpretations:

Decoherence, the measurement problem, and interpretations of quantum mechanics
Rev. Mod. Phys. 76, 1267–1305 (2005)
http://rmp.aps.org/abstract/RMP/v76/i4/p1267_1

Good advice. As I'm really interested, I've already looked for lots of papers and this one is on my list too. I'm afraid the list is too long though, with lots of unneccessary information.

Why would you say that it complicates things result-wise?

Because it makes the same predictions at the cost of being non-local (and non-linear?). I have a book about Bohm Mechanics I'm eager to read, however I'm slightly losing interest in this interpretation since it lacks nice properties the Schroedinger equation has.

 

[Vanadium 50]

By definition, all interpretations of the same theory have exactly the same predictions. If the predictions are different, they are different theories. By definition, therefore, interpretations are untestable. If they were testable, they wouldn't be interpretations.

One area of confusion is that some proponents of some interpretations claim testability. You can't have it both ways - if it makes different predictions, it's not the same as QM, and if it makes the same predictions, how can you tell?

 

[nonequilibrium]

Because it makes the same predictions at the cost of being non-local (and non-linear?).

Where are you basing this on? The (same) Schrödinger equation still holds true in the De Broglie-Bohm theory, so it's just as linear as orthodox QM. And as for non-locality: this doesn't change any of the math. I've never quite understood what the objections against a non-local physical picture could be if the only alternative is no physical picture at all (okay this statement is perhaps a bit bold, but it's to get an idea across that's worth a thought). It can also be argued that non-locality is inherent in all "versions" of QM; it simply becomes more explicit when you're specifying and underlying physical reality. Anyway, these arguments are not meant to convince you that the Bohmian interpretation is the best, certainly not, but is meant to convince you that those arguments you bring up are irrelevant. (Disclaimer: re-reading my post, my sentences could be read in a harsh tone. This isn't the intention! I think it's good that you're interested in interpretations. Sometimes it's easy to misinterpret someone's "tone" when you can only read what he says. Best of luck!)

 

[StevieTNZ]

By definition, all interpretations of the same theory have exactly the same predictions. If the predictions are different, they are different theories. By definition, therefore, interpretations are untestable. If they were testable, they wouldn't be interpretations.

One area of confusion is that some proponents of some interpretations claim testability. You can't have it both ways - if it makes different predictions, it's not the same as QM, and if it makes the same predictions, how can you tell?

Different predictions result if the standard interpretation holds in the thought experiment Ghirardi proposes.

 

[Gerenuk]

Where are you basing this on? The (same) Schrödinger equation still holds true in the De Broglie-Bohm theory, so it's just as linear as orthodox QM. And as for non-locality: this doesn't change any of the math. I've never quite understood what the objections against a non-local physical picture could be if the only alternative is no physical picture at all (okay this statement is perhaps a bit bold, but it's to get an idea across that's worth a thought).

The Schrödering is local, deterministic, linear and the simplest equation one can imagine. I believe it's a pity to lose this features for the very first idea about reality that came to people's minds. So at some point I'd rather think an alternative interpretation of what the wavefunction means, than squeeze a simple equation into a complicating form.
But ideas and speculations are not part of this forum, so I'd rather listen to ideas which interpretation or alternative QM could make a difference :)

 

[Vanadium 50]

Different predictions result if the standard interpretation holds in the thought experiment Ghirardi proposes.

Then it's a different theory. That's what being a different theory means.

 

[StevieTNZ]

Then it's a different theory. That's what being a different theory means.

... therefore entails Copenhagen Interpretation isn't a valid interpretation for QM.

 

[ThomasT]

Is there an interpretation of quantum mechanics, which could make a difference to future calculations and results? Maybe an interpretation which could rewrite and simplify the algebra? Or one which has new testible results which when correct would change the quantum mechanical equations to make them more precise or simpler?

I mean there are popular interpretations like many world interpretation, but it is hard to see why one should put up a theory like this which is neither more powerful nor more intuitive than a copenhagen interpretation. Also Bohm might be easy to grasp for the human mind, but result-wise it only complicates things?

Regarding the question in the title of the thread, the answer is that no interpretation of QM has made a (quantitatively measurable) difference. So, you're left with the bare bones QM math, and how successfully you're able to apply that (when it becomes apparent that you need to) depends on how fluent you are with it, your ingenuity, the breadth and depth of your knowledge of your subject matter, etc.

The current status quo, afaik, is that 'interpretational issues' are just so much fluff wrt applied physics.

If you have a particular question wrt how QM might be applied to something that you're working on, then maybe somebody here can offer some insights.

Otherwise, I would just direct you to the posts of Vanadium 50 and aimforclarity, the only, afaik, physics phd's who've responded to your question thus far.

This is not to say that your question isn't a good one. But what you're really asking is, imo, whether current QM can be the basis of a more encompassing and deeper theory of nature. And I suppose, I hope at least, that there are some really smart people working on this pretty much continually. And I also suppose that when/if they come up with something important, then they'll certainly publish it. But, afaik, and imho, no extant interpretations of QM hold the promise of a deeper, more 'realistic', QM.

 

[bohm2]

When you think about it almost any theory can be made to have many different interpretations but then one has to add so many corollaries to it that it's dismissed on principles of simplicity/elegance, etc. Think about relativity. There are really 3 different interpretations:

Three interpretations of relativity theory

Experimentally verifiable facts: x and t coords of events, measured in any inertial reference system, are related to x and t coords of same events, as measured in any other inertial reference system, by the Lorentz transformations.

1. Einsteinian interpretation: Classical 3+1 ontology of space and time. Inertial frames all equivalent. Problems: Can be regarded as fantastical as events pop in and out of reality as we switch reference frames. Length contraction/time dilation real physical effects (not observation perspective) but unclear why objects enduring through time suffer these (reciprocal!) effects just because in relative motion.

2. Minkowksian interpretation: 3d objects don’t suffer length contraction/time dilation for simple reason that 3d objects don’t exist. Reality is 4-dimensional i.e. spacetime. ‘Ball moving in space’ actually 4d worldtube with all 3d spacelike slices equally real. Length contraction/time dilation ‘perspective effects’. Problems: No objective distinction between past, present and future - can’t speak of objective present world in space or of ‘temporal becoming’ (consciousness?). All 3d observers at different times equally real - nothing singles out one as more real than others.

3. Lorentzian interpretation: Preserves classical notions of 3+1 space and time. Single preferred frame (‘ether’ if you like) and absolute simultaneity. Causal explanation for length contraction/time dilation with respect to absolute space. Only interpretation with unified objective reality, temporal becoming, and causal explanations. Problems: Usually stated can’t detect preferred frame.

Physicists chose one over the other for reasons of simplicity/elegance, I think? With QM, it's harder because all interpretations are equally hard to swallow, or so it seems.

http://www.tcm.phy.cam.ac.uk/~mdt26/PWT/lectures/bohm5.pdf

 

[nonequilibrium]

The Schrödering is local, deterministic, linear and the simplest equation one can imagine. I believe it's a pity to lose this features for the very first idea about reality that came to people's minds.

I don't quite get what you're getting at. Are you under the impression that de Broglie-Bohm changes the Schrödinger equation?

 

[ThomasT]

When you think about it almost any theory can be made to have many different interpretations but then one has to add so many corollaries to it that it's dismissed on principles of simplicity/elegance, etc. Think about relativity. There are really 3 different interpretations:

Physicists chose one over the other for reasons of simplicity/elegance, I think? With QM, it's harder because all interpretations are equally hard to swallow, or so it seems.

I don't think that all QM interpretations are equally hard to swallow -- just the one's that entail a metaphysical picture that seems to contradict our experience ... such as MWI or dBB. The Copenhagen interpretation is essentially an instrumentalist one. And, afaik, it's the CI, combined with the Born/probabilistic interpretation that most working physicists think in terms of when applying QM. In other words, there's no way to know, qualitatively, the reality underlying instrumental behavior -- so, when you've got real problems to solve you just accept the simplest, most straightforward, interpretations of the QM math, which seem to be the CI (in its simplest, instrumentalist form) along with the Born/probabilistic interpretation(s).

The hard thing to get away from is the idea that QM, in its current form, is a description of the real physical reality, of nature. People (most everybody I would suppose) who use the Minkowskian interpretation of SR have the same problem. What I was taught, and what I try to keep in mind, is that these 'interpretations', any 'interpretations', of physical theories are not to be taken as descriptions of 'reality'.

 

[bohm2]

I don't think that all QM interpretations are equally hard to swallow -- just the one's that entail a metaphysical picture that seems to contradict our experience ... such as MWI or dBB. What I was taught, and what I try to keep in mind, is that these 'interpretations', any 'interpretations', of physical theories are not to be taken as descriptions of 'reality'.

An instrumental approach is also a metaphysical perspective. Most physicists who espouse these models aren't doing so from a "naive realist" perspective but from a "scientific realist" perspective and there's a difference. If physical theories aren't trying to model/describe some aspect of "reality" what are they all about? And what is it that makes us change/update our models as science/physics progress?

 

[ThomasT]

An instrumental approach is also a metaphysical perspective. Most physicists who espouse these models aren't doing so from a "naive realist" perspective but from a "scientific realist" perspective and there's a difference. If physical theories aren't trying to model/describe some aspect of "reality" what are they all about?

What physical theories are unarguably and unambiguously about is the behavior of instruments. Mathematical models might reflect a certain 'vision' of the underlying reality, or they might not. Consider the Heisenberg 'picture'. Does that give you a visualizable apprehension of an underlying reality?

And what is it that makes us change/update our models as science/physics progress?

What makes physicists change/update their models is the behavior of instruments. Nobody knows what's happening in the reality underlying that behavior. But inferences/guesses regarding the underlying reality are made, based on the instrumental behavior and our sensory experience.

 

[Gerenuk]

The current status quo, afaik, is that 'interpretational issues' are just so much fluff wrt applied physics.
If you have a particular question wrt how QM might be applied to something that you're working on, then maybe somebody here can offer some insights.
This is not to say that your question isn't a good one. But what you're really asking is, imo, whether current QM can be the basis of a more encompassing and deeper theory of nature.
[...]
But, afaik, and imho, no extant interpretations of QM hold the promise of a deeper, more 'realistic', QM.

You are absolutely right. In fact I don't have a particular problem, but I rather want explore ways to interpret the way function a better way. I want to understand why guessing the Schrödinger equation works and what is the bare minimum to set up QM. One key question would be why <x|p>=exp(ikx)
Anyway... :)

I don't quite get what you're getting at. Are you under the impression that de Broglie-Bohm changes the Schrödinger equation?

It's only about notation. Schrödinger is simple and Bohm twisted and it hides the underlying features.

 

[RUTA]

By definition, all interpretations of the same theory have exactly the same predictions. If the predictions are different, they are different theories. By definition, therefore, interpretations are untestable. If they were testable, they wouldn't be interpretations.

True, but an interpretation can suggest a new approach to fundamental physics, e.g., Relational Blockworld.

 

[bohm2]

What physical theories are unarguably and unambiguously about is the behavior of instruments. Mathematical models might reflect a certain 'vision' of the underlying reality, or they might not. Consider the Heisenberg 'picture'. Does that give you a visualizable apprehension of an underlying reality?

What makes physicists change/update their models is the behavior of instruments. Nobody knows what's happening in the reality underlying that behavior. But inferences/guesses regarding the underlying reality are made, based on the instrumental behavior and our sensory experience.

Most scientific or ontic structural realists don't claim that our models are duplicate copies of mind-independent reality, only that they are guided by that reality. The theoretical abstractions of the physicist cannot be just the result of induction from sense data. There is genuinely creative, theoretical work that is done that go way beyond the instruments or our observations as they involve lawful generalizations and reliable predictions that are applicable way beyond our instruments. The data and observations are useful and have an instrumental character but they are of no particular interest in themselves, "but only insofar as they constitute evidence that permits one to determine fundamental features of the real world" (at least, within our cognitive limitations). Of course, the question which divides philosophers is: "what is the nature of this 'non-empirical element'? Does it belong to the real world or is it a product of our minds? I'm not sure? But I can't see how one can have genuine progress in science if there wasn't some match between the two. Why the match or at least partial match? I have no clue.

 

[Vanadium 50]

True, but an interpretation can suggest a new approach to fundamental physics.

So can getting conked on the head by an apple. That does not suggest that a good path forward is to be pelted by apples.

 

[RUTA]

So can getting conked on the head by an apple. That does not suggest that a good path forward is to be pelted by apples.

Certainly the advice one should give young theorists is not to squander their time sitting under apple trees. Likewise, Mermin was told to "shut up and calculate" when he sought an interpretation of QM as a grad student. Let's face it, no one knows what will eventually inspire the next revolution in physics. So, thankfully, some of them ignore this sage advice and seek inspiration as they see fit. And, some find such inspiration via interpretations of QM.

 

[xristy]

It does seem that a fair amount of physics such as Aspect, GHZ, Quantum Computing and so forth has been done as a result of EPR, Bell and related pondering of interpretation / extension via hidden variables.

 

[Demystifier]

I've never quite understood what the objections against a non-local physical picture could be if the only alternative is no physical picture at all

How about this alternative?
http://xxx.lanl.gov/abs/1112.2034
This is a kind of hybrid between local "Copenhagen" interpretation and nonlocal Bohmian interpretation. It retains locality of the former and a physical picture (certain particle trajectories) of the latter.

 

[xristy]

Another interpretation would be Griffiths Consistent Histories: 1, 2 and 3 which is local, real and with no hidden variables.

 

[Demystifier]

Another interpretation would be Griffiths Consistent Histories: 1, 2 and 3 which is local, real and with no hidden variables.

Every local interpretation of QM has some mayor "but" (that is, give up of some common-sense property one would naively except that a physical theory should possess), as you can see here:
https://www.physicsforums.com/blog.php?b=3622

My question to you is: What is the mayor "but" for the consistent-histories interpretation?
In other words, what is the mayor disadvantage of the consistent-histories interpretation in comparison with other interpretations?

 

[Demystifier]

Every local interpretation of QM has some mayor "but" (that is, give up of some common-sense property one would naively except that a physical theory should possess), as you can see here:
https://www.physicsforums.com/blog.php?b=3622

My question to you is: What is the mayor "but" for the consistent-histories interpretation?
In other words, what is the mayor disadvantage of the consistent-histories interpretation in comparison with other interpretations?

Since you have not answered my question, I have decided to find the answer by myself. In particular, in the Conclusion of
http://lanl.arxiv.org/abs/1110.0974
Griffiths says:
"What he appears to find objectionable is that the histories rules are not identical to those of classical propositional logic. This difference, however, is not grounds for declaring the histories rules inconsistent."

So, I would conclude that the consistent histories interpretation of QM is local, BUT with the price that the classical propositional logic is not valid.

 

[xristy]

Since you have not answered my question, I have decided to find the answer by myself. In particular, in the Conclusion of
http://lanl.arxiv.org/abs/1110.0974
Griffiths says:
"What he appears to find objectionable is that the histories rules are not identical to those of classical propositional logic. This difference, however, is not grounds for declaring the histories rules inconsistent."

So, I would conclude that the consistent histories interpretation of QM is local, BUT with the price that the classical propositional logic is not valid.

I apologize for taking my time to conjure an answer. I was thinking to say that the "but" is the baggage of the extra care one has to take in determining which histories are compatible. I think this is equivalent to the use of a non-classical logic. However, I was reluctant to give such an answer since it doesn't seem much of a "but" to employ a non-classical logic - which I think is exactly Griffiths' position.

So what I really have been thinking is that there is no "but" w.r.t. the Consistent Histories approach.

 

[Demystifier]

So what I really have been thinking is that there is no "but" w.r.t. the Consistent Histories approach.

Of course there is, just as for any other interpretation of QM. Otherwise, ALL physicists would accept that interpretation as the best one.

 

[xristy]

There are likely lots of reasons for physicists to not embrace a particular interpretation however are they all equally reasonable?

Where is it required that classical propositional logic be the appropriate logic for reasoning about quantum phenomena?