New Quantum Interpretation Poll

[Demystifier]

Sounds like a nice gedanken interpretation. Or do you think many people will stick to it in the future? ;-)

Probably not, but who knows?

Is it formally compatible with all assumptions of Bell's theorem? If yes, how is the experimental violation explained? If no, what assumptions are violated?

The Bell theorem assumes that there is reality (hidden variables) associated with entangled particles and/or separated detectors of two particles. This assumption is not satisfied here. Reality is associated only with observers whose role is to act as local coincidence counters. (See Fig. 1 in the paper.)

 

[bohm2]

The poll paper was also discussed in Nature:

Perhaps the fact that quantum theory does its job so well and yet stubbornly refuses to answer our deeper questions contains a lesson in itself,” says Schlosshauer. Possibly the most revealing answer was that 48% believed that there will still be conferences on the foundations of quantum theory in 50 years time.

Experts still split about what quantum theory means
http://www.nature.com/news/experts-still-split-about-what-quantum-theory-means-1.12198

 

[bohm2]

For completion, this poll was also recently discussed by cosmologist Sean Carroll in his blog and the recent video:

I’ll go out on a limb to suggest that the results of this poll should be very embarrassing to physicists. Not, I hasten to add, because Copenhagen came in first, although that’s also a perspective I might want to defend (I think Copenhagen is completely ill-defined, and shouldn’t be the favorite anything of any thoughtful person). The embarrassing thing is that we don’t have agreement. Think about it-quantum mechanics has been around since the 1920′s at least, in a fairly settled form. John von Neumann laid out the mathematical structure in 1932. Subsequently, quantum mechanics has become the most important and best-tested part of modern physics. Without it, nothing makes sense. Every student who gets a degree in physics is supposed to learn QM above all else. There are a variety of experimental probes, all of which confirm the theory to spectacular precision. And yet-we don’t understand it. Embarrassing. To all of us, as a field (not excepting myself).

The Most Embarrassing Graph in Modern Physics
http://www.preposterousuniverse.com/blog/2013/01/17/the-most-embarrassing-graph-in-modern-physics/

QM:An embarassment

 

[DrChinese]

At the edge of knowledge in any scientific field, there is "embarrassment" such as this. What happened before the big bang? Cosmologists don't agree on that either. Was the evolution of intelligence in the universe likely? Experts don't agree about that.

 

[Zarqon]

For completion, this poll was also recently discussed by cosmologist Sean Carroll in his blog and the recent video:

The Most Embarrassing Graph in Modern Physics
http://www.preposterousuniverse.com/blog/2013/01/17/the-most-embarrassing-graph-in-modern-physics/

QM:An embarassment

I cannot really say I agree with him here. I don't think it's embarrassing at all. In fact the opposite, I think it means it's have a very difficult and interesting question that deserves to be mentioned more often. I also think we should not go around calling it embarrassing because it sends bad signals to the general population. All knowledge starts from being unknown, and contrary to some other interestgroups in our society, we as scientists should freely admitt it whenever we don't know something. It's not something strange it's natural.

 

[Demystifier]

I cannot really say I agree with him here. I don't think it's embarrassing at all. In fact the opposite, I think it means it's have a very difficult and interesting question that deserves to be mentioned more often. I also think we should not go around calling it embarrassing because it sends bad signals to the general population. All knowledge starts from being unknown, and contrary to some other interestgroups in our society, we as scientists should freely admitt it whenever we don't know something. It's not something strange it's natural.

I absolutely agree!

 

[kith]

Matt Leifer has made an excellent post in the comment section of the preposterousuniverse blog. According to him, the scientific relevance of quantum foundations is not to find the "right" interpretation to the already existing theory (because that's metaphysical), but the fact that different interpretations suggest different ways to solve the known problems of physics which probably require a theory that goes beyond QM.

 

[bohm2]

Another survey came out today with very different results:

This is a somehow surprising result. The elsewise sovereign Copenhagen interpretation loses ground against the de Broglie-Bohm interpretation. This is partly the inflluence of decided minorities in small populations, because the participants of the conference were all but representative of the whole physicists' community. Not surprisingly, the outcome is well different from the observed distribution by Tegmark or Schlosshauer et al.

Another Survey of Foundational Attitudes Towards Quantum Mechanics
http://lanl.arxiv.org/pdf/1303.2719.pdf

 

[Quantumental]

Another survey came out today with very different results:

Another Survey of Foundational Attitudes Towards Quantum Mechanics
http://lanl.arxiv.org/pdf/1303.2719.pdf

Interesting, but such a small sample.
What I cannot for the life of me understand is why someone hasn't just sent a email to say 200 quantum physicists with the questionaire. it would give a much much more interesting snapshot.

Once again the answers of this poll is so ****ing weird and inconsistent, it's pretty clear the answerers aren't even sure wtf they think about the issue.

I think what is needed is a BIG poll, these tiny conference polls are literally not even a drop in the ocean. Sure they are slightly interesting, but that's it.

 

[Demystifier]

Another Survey of Foundational Attitudes Towards Quantum Mechanics
http://lanl.arxiv.org/pdf/1303.2719.pdf

According to this survey, the top 3 interpretations are:
1. I have no preferred interpretation - 44%
2. Shut up and calculate - 17 %
3. De-Broglie Bohm - 17 %

Given that 1. and 2. are not really specific interpretations at all, it can be said that De-Broglie Bohm, at this conference at least, is the most popular specific interpretation.

 

[martinbn]

Only 12 physicists, most of them master students or early Ph.D. students. May be later on they will have a preferred interpretation.

 

[aphirst]

There is an assumption (as someone has pointed out) made by the bohm interpretation, which is that the initial distribution of particle positions is made to agree with the square of the Schrodinger wave function, but I don't see how in a realistic model, that makes sense. If you only have a single electron, for instance, what sense does it make that it has a "distribution"?

I know it's been a month since this thread was last bumped, but I really can't read this and let it slide.

You don't have to simply assume that the initial distribution goes as |ψ|². Running dynamics simulations with unrelated initial conditions results in the distribution dropping out. Quantum equilibrium isn't a "postulate" in the same way that other interpretations relate |ψ|² to "probabilities" (whatever they do or don't say they're probabilities of...)

 

[Demystifier]

I know it's been a month since this thread was last bumped, but I really can't read this and let it slide.

You don't have to simply assume that the initial distribution goes as |ψ|². Running dynamics simulations with unrelated initial conditions results in the distribution dropping out. Quantum equilibrium isn't a "postulate" in the same way that other interpretations relate |ψ|² to "probabilities" (whatever they do or don't say they're probabilities of...)

Yes, that needs to be repeated over and over again.

Just as not so long time ago it was needed to repeat over and over again that the Bell theorem does not exclude general hidden variables (including the Bohmian ones), but only local hidden variables. Fortunately, it seems that now a significant majority of physicists appreciates that.

 

[bohm2]

Just for completion, another poll done with vastly different results with author's insightful (in my opinion) comments hi-lited:

Here we report the results of giving this same survey to the attendees at another recent quantum foundations conference. While it is rather difficult to conclude anything of scientific significance from the poll, the results do strongly suggest several interesting cultural facts – for example, that there exist, within the broad field of “quantum foundations”, sub-communities with quite different views, and that (relatedly) there is probably even significantly more controversy about several fundamental issues than the already-significant amount revealed in the earlier poll...

In the SKZ results, b. Copenhagen (42%) and e. Information-based/information-theoretical (24%) received the highest response rates, while c. de Broglie - Bohm received zero votes of endorsement. SKZ write explicitly that “the fact that de Broglie - Bohm interpretation did not receive any votes may simply be an artifact of the particular set of participants we polled.” Our results strongly confirm this suspicion. At the Bielefeld conference, choice c. de Broglie - Bohm garnered far and away the majority of the votes (63%) while b. Copenhagen and e. information-based / information-theoretical received a paltry 4% and 5% respectively. It is also interesting to compare results on this question to the older (1997) survey conducted by Max Tegmark. Tegmark, finding that 17% of his respondents endorsed a many-worlds / Everett interpretation, announced this as a “rather striking shift in opinion compared to the old days when the Copenhagen interpretation reigned supreme.” Our results clearly suggest, though, that any such interpretation of these sorts of poll results – as indicating a meaningful temporal shift in attitudes – should be taken with a rather large grain of salt. It is almost certainly not the case, for example, that while a “striking shift” toward many-worlds views occurred in the years prior to 1997, this shift then stalled out between 1997 and 2011 (the response rate endorsing Everett being about the same in the Tegmark and SKZ polls), and then suddenly collapsed (with the majority of quantum foundations workers now embracing the de Broglie - Bohm pilot-wave theory).

Instead, the obviously more plausible interpretation of the data is that each poll was given to a very different and highly non-representative group. The snapshots reveal much more about the processes by which it was decided whom should be invited to a given conference, than they reveal about trends in the thinking of the community as a whole. We note finally that insofar as our poll got more than twice as many respondents as the SKZ poll (which those authors had described as “the most comprehensive poll of quantum-foundational views ever conducted”) it is now apparently the case that the de Broglie - Bohm pilot-wave theory is, by an incredibly large margin, the most endorsed interpretation in the most comprehensive poll of quantum foundational views ever conducted. For the reasons we have just been explaining, this has almost no meaning, significance, or implications, beyond the fact that lots of “Bohmians” were invited to the Bielefeld conference. But it does demonstrate rather strikingly that the earlier conferences (where polls were conducted by Tegmark and SKZ) somehow failed to involve a rather large contingent of the broader foundations community. And similarly, the Bielefeld conference somehow failed to involve the large Everett-supporting contingent of the broader foundations community.

Yet Another Snapshot of Foundational Attitudes Toward Quantum Mechanics
http://lanl.arxiv.org/pdf/1306.4646.pdf

 

[Demystifier]

Even though, as before, the sample is not representative, it is always interesting to see the top 3 list:
1. De Broglie-Bohm - 63%
2. Objective Collapse - 16 %
3. I have no preferred interpretation - 11 %

 

[stevendaryl]

I know it's been a month since this thread was last bumped, but I really can't read this and let it slide.

You don't have to simply assume that the initial distribution goes as |ψ|². Running dynamics simulations with unrelated initial conditions results in the distribution dropping out. Quantum equilibrium isn't a "postulate" in the same way that other interpretations relate |ψ|² to "probabilities" (whatever they do or don't say they're probabilities of...)

I don't understand that. Let's take the case of a single particle. In the Bohm interpretation, it always has a definite location. So unless the wave function is a delta-function, it's square won't agree with the actually distribution of particles.

 

[kith]

Thanks bohm2, this is quite interesting. I was interested in the exact topics of the conferences where the polls were taken. Here they are:

Tegmark: "Fundamental Problems in Quantum Theory" 1997
Schlosshauer et al.: "Quantum Physics and the Nature of Reality" 2011
Norsen & Nelson: "Quantum Theory Without Observers" 2013

Arguably, the topic of the last conference is narrower. Researchers who favor an observer-dependent interpretation may have been discouraged to attend.

 

[Demystifier]

I don't understand that. Let's take the case of a single particle. In the Bohm interpretation, it always has a definite location. So unless the wave function is a delta-function, it's square won't agree with the actually distribution of particles.

You should think of it as analogous to classical statistical mechanics. A single particle always has a definite position, energy, etc. But if you have a STATISTICAL ENSEMBLE of particles, then each particle in the ensemble may have a different position, energy, etc. In particular, in a canonical ensemble in a thermal equilibrium, the probability that the particle has energy E is proportional to e^(-E/kT). This probability is an a priori probability, describing your knowledge about a particle before you determine its actual properties. Once you determine that the actual energy has some value e, then you can replace e^(-E/kT) with the delta function delta(E-e).

 

[stevendaryl]

You should think of it as analogous to classical statistical mechanics. A single particle always has a definite position, energy, etc. But if you have a STATISTICAL ENSEMBLE of particles, then each particle in the ensemble may have a different position, energy, etc. In particular, in a canonical ensemble in a thermal equilibrium, the probability that the particle has energy E is proportional to e^(-E/kT). This probability is an a priori probability, describing your knowledge about a particle before you determine its actual properties. Once you determine that the actual energy has some value e, then you can replace e^(-E/kT) with the delta function delta(E-e).

I'm not convinced that this works. Initially, suppose that the particle can be in anyone of 1,000,000 different boxes. You detect it in a specific box. Then you let it evolve without interference for a while. What wave function is appropriate after you detected it in the box? According to the "collapse" interpretation, you use a wave function that is zero everywhere except in the box where you detected it. But according to the interpretation that you are describing, the wave function refers, not to this single particle, but an ensemble of identical particles. The fact that you discovered this particle in a particular box doesn't imply anything about the vast number of other particles in the ensemble. So the wave function, which refers to the ensemble, is not localized on the box where you discovered the particle.

So that seems to me to be a big, empirically testable, difference between the interpretation you are describing and the "collapse" interpretation. After the initial detection, they are using different wave functions, one collapsed and one not.

 

[Demystifier]

I'm not convinced that this works. Initially, suppose that the particle can be in anyone of 1,000,000 different boxes. You detect it in a specific box. Then you let it evolve without interference for a while. What wave function is appropriate after you detected it in the box? According to the "collapse" interpretation, you use a wave function that is zero everywhere except in the box where you detected it.

That's correct.

But according to the interpretation that you are describing, the wave function refers, not to this single particle, but an ensemble of identical particles.

No, that's not exactly so according to the interpretation I am describing. Instead, see
https://www.physicsforums.com/showpost.php?p=4413956&postcount=84

The fact that you discovered this particle in a particular box doesn't imply anything about the vast number of other particles in the ensemble.

True.

So the wave function, which refers to the ensemble, is not localized on the box where you discovered the particle.

True, but suppose that you have discovered many particles in the same box. In that case the localized wave function describes an sub-ensemble of all the particles found in that box.

So that seems to me to be a big, empirically testable, difference between the interpretation you are describing and the "collapse" interpretation.

There is a big conceptual difference, but nobody yet found a way to make it testable. The main reason is the phenomenon of decoherence (which does not depend on the interpretation you use), which effectively washes out all testable differences.

After the initial detection, they are using different wave functions, one collapsed and one not.

That is true. In Bohmian mechanics one distinguishes the wave function of the universe (which never collapses) and effective wave function (which for practical purposes can be thought of collapsing).

 

[bohm2]

An interesting critical post by a non-Bohmian that attended that conference "QM without observers III" where that last poll linked above was completed:

Guest post on Bohmian Mechanics, by Reinhard F. Werner
http://tjoresearchnotes.wordpress.c...st-on-bohmian-mechanics-by-reinhard-f-werner/

What is really interesting is the exchange between the poster (Reinhard F. Werner), Matt Leifer, Tim Maudlin, Matt Pusey (of PBR theorem fame) and Travis Norsen. What I found really interesting is the heated exchange on the topic of Bell's theorem and implications for "realism" and if local non-realism is even comprehensible. This topic has always been difficult for me to understand. Some interesting quotes:

Matt Leifer

It is a fairly standard mantra that Bell’s theorem is based on the conjunction of realism and locality and so one can choose to reject one of them whilst keeping the other. As you say, Bohmians opt to throw out locality. As for the other position, i.e. locality without realism, I have a lot of trouble understanding what it is even supposed to mean...In fact, it seems to me that locality, in any sense that is even tangentially related to Bell’s theorem, requires realism for its very definition. You need to be able to say that there to be some things that objectively exist in the world in order to say whether changing them at one location affects them at some other. Hence, in my view, it is more accurate to say that holders of operational positions are rejecting both realism AND locality (in any sense that is relevant to Bell’s theorem).

Tim Maudlin:

Nothing does, except a confusion about the principles Bell used to derive his theorem. There is no supposition of “realism” in any sense in this theorem. If you think otherwise, point it out: it is, after all, a piece of mathematics.

Travis Norsen:

“Signal locality” (or “local commutativity”) is simply not an assumption of Bell’s theorem (either/any of them) and nobody who had actually read Bell’s papers (in several of which he goes to great lengths specifically to *distinguish* “signal locality” from the locality assumption that is actually used in the theorem) could possibly harbor this misconception. Nor is “realism” (in anything but the most basic sense, denial of which would render “locality” — in any sense — completely meaningless, as Matt L already pointed out) an assumption of Bell’s theorem.

Edit: Actually Norsen in a post in this forum does provide a local and non-realist (in some sense) model:

Here's a model that non-realistic but perfectly Bell local: each particle has no definite, pre-existing, pre-scripted value for how the measurements will come out. Think of each particle as carrying a coin, which, upon encountering an SG device, it flips -- heads it goes "up", tails it goes "down". That is certainly not "realistic" (in the sense that people are using that term here) since there is no fact of the matter, prior to the measurement, about how a given particle will respond to the measurement; the outcome is "created on the fly", so to speak. And it's also perfectly local in the sense that what particle 1 ends up doing is in no way influenced by anything going on near particle 2, or vice versa. Of course, the model doesn't make the QM/empirical predictions. But it's non-realist and local. And hence a counter-example to any claim that being Bell local requires/implies being "realist".

 

[harrylin]

[..] Actually Norsen in a post in this forum does provide a local and non-realist (in some sense) model:

That's interesting indeed, as I think that most people - and maybe even Einstein - would call a coin-flipping model "realistic".

 

[Demystifier]

Concerning the question of what locality without realism is even supposed to mean, I also had difficulties with it, until I found my own model for such a thing:
http://arxiv.org/abs/1112.2034 [Int. J. Quantum Inf. 10 (2012) 1241016]