Survival of de Broglie-Bohm Theory in Latest Challenge - physicsworld.com

[DevilsAvocado]

Got some exciting news from a PF Mentor:

http://physicsworld.com/cws/article/news/44580"

Quantum theory survives latest challenge - physicsworld.com
...

Glasgow student Jacquie Romero did the experiment by firing an ultraviolet laser into an optical crystal designed to split the high-energy photons into pairs of entangled infrared photons. These went on to computer-controlled holograms, which were set to filter out roughly complementary orbital angular momentum states. Photons that passed the holograms were then counted by a single-photon detector.
...

"The main outcome is really a philosophical result," says Franke-Arnold. Entangled particles can't be described as individual entities, not even with a telepathic connection to their partners.

Simon Gröblacher of the University of Vienna points out that these experiments rule out realism only for a large class of nonlocal theories – still others aren't described by Leggett’s inequality.

And the actual paper:

http://iopscience.iop.org/1367-2630/12/12/123007
Violation of Leggett inequalities in orbital angular momentum subspaces
J Romero, J Leach, B Jack, S M Barnett, M J Padgett and S Franke-Arnold
J Romero et al 2010 New J. Phys. 12 123007
doi: 10.1088/1367-2630/12/12/123007​

As far as I can tell this is stunning news. It rules out large number of non-local realism models.
Will the de Broglie-Bohm theory survive this?

 

[lugita15]

I thought that any refutation of de Broglie-Bohm theory would refute quantum mechanics itself. Isn't there a famous theorem to that effect?

 

[DevilsAvocado]

I thought that any refutation of de Broglie-Bohm theory would refute quantum mechanics itself.

I don’t think that’s correct...

We are talking about a test of Leggett's inequality, and according to Bell's theorem Local Realism is not compatible with the predictions of QM.

But there’s nothing preventing us from having a non-local non-realism model... afaict...

(A better word for non-realism is http://plato.stanford.edu/entries/physics-holism/" )

 

[p764rds]

Got some exciting news from a PF Mentor:
And the actual paper:

http://iopscience.iop.org/1367-2630/12/12/123007
Violation of Leggett inequalities in orbital angular momentum subspaces
J Romero, J Leach, B Jack, S M Barnett, M J Padgett and S Franke-Arnold
J Romero et al 2010 New J. Phys. 12 123007
doi: 10.1088/1367-2630/12/12/123007​

As far as I can tell this is stunning news. It rules out large number of non-local realism models.
Will the de Broglie-Bohm theory survive this?

'not even with a telepathic connection to their partners'

If we break weak causality between spawning and observation then the particles 'receive' their final states at the start, even though the final states are not yet determined . This is achieved *in principle* by information being passed from observation time to spawn time - backwards in time. So the 'later' observation values become the outset values.
It is still sequential in that spawn precedes observation, but if we let the time difference t -> 0 then we break weak causality (which we are allowed to) and the sequentially known state results are passed directly to particles at outset.

In effect we can then say that the observation time and spawn time are the same and the states are already defined at outset AND they are determined at observation too. A seeming paradox that works if we allow t -> 0. The time difference is (effectively) zero. Thus Leggett, Bells inequalities still hold. This a modification of Bohms Theory and does require an informational reference frame that Bohm's Theory also requires.

 

[Demystifier]

I thought that any refutation of de Broglie-Bohm theory would refute quantum mechanics itself. Isn't there a famous theorem to that effect?

Exactly!

 

[Demystifier]

I don’t think that’s correct...

Why not? What, in your opinion, is wrong in the theorem that says that it's correct?

 

[cryptist]

Originally Posted by lugita15 View Post

I thought that any refutation of de Broglie-Bohm theory would refute quantum mechanics itself. Isn't there a famous theorem to that effect?

Exactly!

Could you give the link of the article that proves this, please?
Thank you.

 

[DevilsAvocado]

a famous theorem

the theorem

Gentlemen, could we stop talking in riddles?

Demystifier, I know you are a well educated and genuine scientist. You can’t for real be saying that there are scientific proofs in dBB saying that if this non-local realism model is wrong, then everything else in QM is also wrong??

 

[DevilsAvocado]

This is achieved *in principle* by information being passed from observation time to spawn time - backwards in time.

This looks like http://en.wikipedia.org/wiki/Retrocausality" to me.

 

[Fredrik]

Will the de Broglie-Bohm theory survive this?

Why wouldn't it? Does it satisfy the assumptions that go into the derivation of the inequality? (I don't know dBB, but I expect that it satsifies the first but not the second requirement).

We are talking about a test of Leggett's inequality, and according to Bell's theorem Local Realism is not compatible with the predictions of QM.

But there’s nothing preventing us from having a non-local non-realism model... afaict...

(A better word for non-realism is http://plato.stanford.edu/entries/physics-holism/" )

I have always disliked such terms, probably because they're never unambiguously defined anywhere. Even the page you're linking to says this right at the start:

Just what holism and nonseparability are supposed to be has not always been made clear, though, and each of these notions has been understood in different ways. Moreover, while some have taken holism and nonseparability to come to the same thing, others have thought it important to distinguish the two.
​

 

[Demystifier]

You can’t for real be saying that there are scientific proofs in dBB saying that if this non-local realism model is wrong, then everything else in QM is also wrong??

What I am saying is that there is a proof that dBB and QM have the same measurable predictions.

 

[DevilsAvocado]

Why wouldn't it? Does it satisfy the assumptions that go into the derivation of the inequality? (I don't know dBB, but I expect that it satsifies the first but not the second requirement).

I don’t know either, but I was hoping that dBB experts like Demystifier could tell us what’s right or wrong. The only thing I know is that the authors are claiming that:

"these experiments rule out realism only for a large class of nonlocal theories"​

So it would be extremely interesting to know if dBB is included in this "large class" (I hope no one denies that dBB is a nonlocal realism model).

I have always disliked such terms, probably because they're never unambiguously defined anywhere.

I agree, it’s vague, but nevertheless we can’t reject that it’s there in Bell's theorem. So if it’s not true that realism holds in physical experiments, we must find out what "not realism" means...

RUTA is using http://en.wikipedia.org/wiki/Regge_calculus" .

 

[DevilsAvocado]

What I am saying is that there is a proof that dBB and QM have the same measurable predictions.

And that goes for all http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics" , right? Anything else would be quite astonishing:

Latest news! A new EPR-Bell experiment in the Many-Worlds-Interpretation gives completely new results that no one ever expected!​

That’s 'brainless', right?

So what I really want to know – Is there anything in dBB that makes it different from the "large class of nonlocal theories" that will have 'problems' with realism, according to this new experiment/paper, and thereby escapes this presumable 'doomsday' for nonlocal realism models?

 

[p764rds]

Yes, and John Cramer is working at present on retrocausality.

 

[Calrik]

Why not? What, in your opinion, is wrong in the theorem that says that it's correct?

I'd agree doesn't it depend on the axioms, in that sense if it conflicts then either QM is wrong or DBT is wrong or both.

As with all interpretations aren't they just different ways of essentially explaining the same thing?

Hence any theory based on them logically must be congruent with QM or fail.

 

[Demystifier]

The only thing I know is that the authors are claiming that:

"these experiments rule out realism only for a large class of nonlocal theories"​

I don't think that this is what they claim. If you take a look at the original scientific paper
http://iopscience.iop.org/1367-2630/12/12/123007
all they say is that they rule out the Legget's non-local hidden variable theory. It can hardly be considered a LARGE class of nonlocal theories.

The moral is:
If you want to know what scientists say, DON'T read what the journalists say.

 

[DevilsAvocado]

I don't think that this is what they claim.

Well, that’s all I was asking for.

dBB do not satisfy Leggett’s assumptions, period.

Then maybe it’s another discussion if "hidden variables" that do not have a well-defined value of polarization are really "real"...? But that’s maybe a topic for another thread.

Case closed.


P.S. I do listen more to PF Mentors than journalists, and look where it has taken me...

 

[Calrik]

Well, that’s all I was asking for.

dBB do not satisfy Leggett’s assumptions, period.

Then maybe it’s another discussion if "hidden variables" that do not have a well-defined value of polarization are really "real"...? But that’s maybe a topic for another thread.

Case closed.


P.S. I do listen more to PF Mentors than journalists, and look where it has taken me...

Not into journalism I hope.

 

[Demystifier]

The only reasons why physicists pay big attention to the Leggett's theory are
1) Because it (unlike dBB) can be easily tested against standard QM.
2) Because Leggett is a winner of the Nobel prize.
And not because it is a very promissing theory covering a large class of possibilities (which it isn't).

 

[p764rds]

The only reasons why physicists pay big attention to the Leggett's theory are
1) Because it (unlike dBB) can be easily tested against standard QM.
2) Because Leggett is a winner of the Nobel prize.
And not because it is a very promissing theory covering a large class of possibilities (which it isn't).

It was an extra experiment worth doing I suppose because it adds to Bells experiments and builds an effective case from which to argue...

:)

 

[Demystifier]

It was an extra experiment worth doing I suppose because it adds to Bells experiments and builds an effective case from which to argue...

:)

Sure, but if there was no reason 2) above, physicists would not pay big attention to it. :zzz:
Of course, I cannot prove it, but ...

 

[yoda jedi]

And that goes for all http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics" , right? Anything else would be quite astonishing:

the Many-Worlds-Interpretation gives...

That’s 'brainless', right?

not so brainless...

...from the many-worlds interpretation of quantum mechanics – an interpretation that we argue is deterministic, local, and realist, but that nonetheless violates the Bell inequality...
...the minimal assumptions* behind Bell’spredictions are locality and “counterfactual definiteness”......
...There is some risk in trying to clarify such a contentious issue. Although the role of counterfactual definiteness in the Bell analysis was identified as early as 1971 **,it is not broadly accepted by the physics community, and there is much debate about the interpretation of the Bell experiment...
.....It appears we have not yet reached the end of research in this field. Researchers are still developing testable theorems about the nature of reality***, allowing us to introduce science into what was once the realm of pure philosophy. On this note, we can look forward to a new generation of debate about physical reality that follows in the footsteps of John Bell....




*varies for various authors.
**Henry Pierce Stapp, “S-matrix interpretation of quantum theory,” Phys. Rev. D 3, 1303–1320 (1971).
*** not just, Counterfactual Definiteness.

http://arxiv.org/PS_cache/arxiv/pdf/0902/0902.3827v4.pdf

 

[DevilsAvocado]

Although the role of counterfactual definiteness in the Bell analysis was identified as early as 1971

Or as early as 1927, when Einstein with respect to the treatment of an incompatible pair tells Schrödinger "ist mir wurst" – literally, it's sausage to me; i.e., he couldn't care less. (Fine 1996, p. 38)

It appears we have not yet reached the end of research in this field.

Agree, and I’m looking forward to a bright future!


P.S. What’s with the "...." ??

 

[DevilsAvocado]

2) Because Leggett is a winner of the Nobel prize.

Okay, so Nobel Laureates is no good.

P.S. Didn’t Louis de Broglie get the Nobel Prize in Physics 1929...??


()

 

[yoda jedi]

P.S. What’s with the "...." ??

text and more text

 

[p764rds]

I hope its the start of new ideas and directions. I feel sure there are rational explanations just near to us, especially regarding entanglement.

 

[Demystifier]

Okay, so Nobel Laureates is no good.

P.S. Didn’t Louis de Broglie get the Nobel Prize in Physics 1929...??


()

Yes, that's why I prefer to call it "Bohmian mechanics".

 

[DevilsAvocado]

Yes, that's why I prefer to call it "Bohmian mechanics".

Hehe, okay I give up... IF you change your username from deMystifier to bohmYstifier!




(...sorry )

 

[Demystifier]

Sure, but if there was no reason 2) above, physicists would not pay big attention to it. :zzz:
Of course, I cannot prove it, but ...

Or maybe I can.
If I am right, then physicists will not pay big attention to this
http://xxx.lanl.gov/abs/1012.5810
recent closely related paper. We shall see ...

 

[Demystifier]

Hehe, okay I give up... IF you change your username from deMystifier to bohmYstifier!




(...sorry )

Or if I refuse to take the Nobel prize.

 

[DevilsAvocado]

Or if I refuse to take the Nobel prize.

Okay! NOW we are talking!


(I will PM my bank account number so that you can transfer the dough when it comes.)