Is action at a distance possible as envisaged by the EPR Paradox.

[Deepak Kapur]

Is action at a distance possible as envisaged by the EPR Paradox?

 

[SpectraCat]

Is action at a distance possible as envisaged by the EPR Paradox?

It's not just possible, it has been experimentally demonstrated. Read up on some of the entanglement threads that have been running on here for a while. Or you could just visit Dr Chinese's website ...

 

[Fredrik]

I'll just add that it's not quite what you might expect "action at a distance" to be. You can't use entanglement to remote control your TV, or send any kind of messages.

 

[DrChinese]

As Fredrik says, the kind of action at a distance entailed by entanglement is not one which allows signaling or causation. It will always be random, a result of an observation which leads to wave function collapse.

 

[ThomasT]

Is action at a distance possible as envisaged by the EPR Paradox?

No. There's no action at a distance (or paradox) involved in EPR -- just some deductions about one particle based on the experimental preparation and detection of the other particle.

 

[Pio2001]

Such a thing would be possible if
1-a non-local hidden variable theory is true.
2-hidden variables can be locally manipulated.

Then Alice just has to change the hidden variables on her side and give them the value that causes result +. Bob thus receives the bit -.

 

[Frame Dragger]

I'll just add that it's not quite what you might expect "action at a distance" to be. You can't use entanglement to remote control your TV, or send any kind of messages.

Sure you could... you just need Classical means to make any sense of it, and then you're limited to 'c' at max. I use IR to control my TV, and that is certainly not FTL. I know you, fredrik understand this, but for the sake of clarity...

 

[DevilsAvocado]

But... even if we cannot use entanglement to send usable information FTL, the particles must clearly be 'communicating' in some way to present the opposite random property, right? And Bell showed there are no local hidden variables involved... or did I miss something?

MWI is the only 'way out' of this is, as I understand...?

 

[Frame Dragger]

But... even if we cannot use entanglement to send usable information FTL, the particles must clearly be 'communicating' in some way to present the opposite random property, right? And Bell showed there are no local hidden variables involved... or did I miss something?

MWI is the only 'way out' of this is, as I understand...?

Well, I don't espouse or believe in it, but there is the Bohmian view (Demystifier and Zenith are the dBB'ers here), there is the Transactional Interpretation... and there are the rest of us who just have no idea, don't want to be purely Instrumentalist pretty much just deal with the cognitive dissonance.

DrChinese is the master of Bell I'd say, and to essentially quote him, Bell shows that no LHV theory can match the prediction of QM. de Broglie-Bohm sidesteps this with NON-Local Hidden Variables, MWI you know about... etc. Bell doesn't really say anything for or against QM, just sets a standard of predictiablity and a test for it.

What that means... is anyone's guess. I don't think you've missed anything. There is still some kind of "Spukhafte Fernwirking"... or a Hidden Variable.

 

[zonde]

But... even if we cannot use entanglement to send usable information FTL, the particles must clearly be 'communicating' in some way to present the opposite random property, right? And Bell showed there are no local hidden variables involved... or did I miss something?

Only if you assume that whole sample in experiments can present the opposite random property.
However if you do not assume that then you can not deduce anything radical out of Bell inequality type experiments.
That is so called unfair sampling possibility.

 

[DevilsAvocado]

Well, I don't espouse or believe in it, but there is the Bohmian view (Demystifier and Zenith are the dBB'ers here), there is the Transactional Interpretation... and there are the rest of us who just have no idea, don't want to be purely Instrumentalist pretty much just deal with the cognitive dissonance.

Thanks for the reply Frame Dragger. Very wise, and I think I want to join your spukhafte-gang of "just-have-no-idea" for the moment... There seems to be more to know about "Spukhafte Fernwirkung"/NLHV... (funny German word )

But, if we accept the cognitive dissonance completely, we might never be able to reach "the grapes", that obviously are there.

Mitch Hedberg: "Sometimes in the middle of the night, I think of something that's funny, then I go get a pen and I write it down. Or if the pen's too far away, I have to convince myself that what I thought of ain't funny."

 

[DevilsAvocado]

... then you can not deduce anything radical out of Bell inequality type experiments.
That is so called unfair sampling possibility.

Okay, that’s a pretty harsh Aspect on the Bells ringing at Einstein’s funeral...

Are you saying that John Bell was totally wrong, and Alain Aspect was totally stupid spending all this time & money in experimentally verifying that Bell's inequalities are physically violated??

Isn’t that a little bit too unfair...?

 

[Frame Dragger]

Thanks for the reply Frame Dragger. Very wise, and I think I want to join your spukhafte-gang of "just-have-no-idea" for the moment... There seems to be more to know about "Spukhafte Fernwirkung"/NLHV... (funny German word )

But, if we accept the cognitive dissonance completely, we might never be able to reach "the grapes", that’s obviously there.

Ahhh the grapes... you're right. Then again, I find curiosity drives me, even if I'm unable to buy into a particular Interpretation. It is a luxury I get by not having to produce my own theories or hypotheses, not being in the field of physics. I realize that isn't an option for everyone, and of course many really believe in their view.

@Zonde: Isn't that a bit of an ongoing debate with you and DrChinese and others (on PF), that is as yet, unsettled here, never mind the world at large?

 

[DevilsAvocado]

... I find curiosity drives me, even if I'm unable to buy into a particular Interpretation. It is a luxury I get by not having to produce my own theories or hypotheses, not being in the field of physics. I realize that isn't an option for everyone, and of course many really believe in their view.

Okay, now I definitely want to join your "spukhafte-gang", where can I buy the member card!?

 

[Frame Dragger]

Okay, now I definitely want to join your "spukhafte-gang", where can I buy the member card!?

You just did? To be fair, I think we both join a gang now, not mine... Spukhafte was Einstein... but he didn't believe in QM's predictions. I think most people feel this way to some degree, but I could be wrong...

 

[DevilsAvocado]

... I think most people feel this way to some degree, but I could be wrong...

Very true, and if I’m not totally wrong, John Bell initially hoped that Einstein’s view was accurate, but had to face the facts his theorem finally showed him. To me, that’s what science is all about; to ask questions – and accept the proven answers.

I’m not particularly fond of solving one strange "spukhafte", by introducing another amazingly more stranger "spukhafte" – without physical proof... (EPR + MWI = no problem). But then again, this might actually turn out to be the actual solution. We just don’t know yet.

The future is interesting and not 100% clear!

PS: If we know that QM & GR is not 100% compatible, then one or both must be (slightly) wrong.

 

[ThomasT]

But... even if we cannot use entanglement to send usable information FTL, the particles must clearly be 'communicating' in some way to present the opposite random property, right?

No. The properties, motion(s) of the entangled particles that are being jointly analyzed are either identical or closely related in some way due to past interaction(s), a common source, or they're parts of an encompassing system.

So there really doesn't need to be any communication or causal link of any sort between the separated particles in order to understand why joint detections of them are correlated wrt some global measurement parameter(s).

And Bell showed there are no local hidden variables involved ...

That's right, but that statement needs some qualification. In the contexts where joint detection attributes are correlated to global measurement parameters the hidden variable that would, if it were known, allow more precise prediction of individual results is simply not relevant.

What's relevant in the joint context is the relationship between the two separated particles.

The oft repeated statement that QM is incompatible with local hidden variables isn't quite true. QM is compatible with lhv formulations of certain setups, such as wrt the individual arms of optical Bell tests. QM is incompatible with lhv formulations of setups where the lhv is irrelevant wrt determining the results, such as wrt the correlations of joint results with some global measurement parameter.

MWI is the only 'way out' of this is, as I understand...?

'Way out' of what -- nonlocality? What nonlocality? If you think that it can be inferred via experimental violations of Bell inequalities or via GHZ inconsistencies, then consider that the physical meaning attributed to BIs and GHZ manipulations associated with Bell tests is rather questionable.

You might start a separate thread exploring exactly how BIs are derived and exactly how the limits imposed by them are connected with the reality of the experimental setups -- and also exactly how the detection attributes (+1s and -1s) involved in GHZ manipulations are connected to EPR elements of reality.

It isn't at all a foregone conclusion, nor has it been definitively demonstrated, that experimental violations of BIs or GHZ inconsistencies have the physical meaning that's been attributed to them by some -- that is, quantum entanglement should not be taken as being synonymous with nonlocality or ftl propagations.

 

[DevilsAvocado]

ThomasT, pardon my French, but this reasoning doesn’t convince me in any way. I may be a layman, but I’m not stupid.

1) Quantum entanglement is a quantum mechanical state of a system of two or more objects.

2) It is generally accepted that there can be no interpretations of quantum mechanics which use local hidden variables.​

I’m no expert; I just use 'common sense' to make up my mind of what is plausible (for the moment), and if I add Bell's theorem:

"No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics."​

To the fact that a lot of serious Bell test experiments have all indicated that Bell's theorem is accurate, and that not one has pointed clearly in the other direction; it’s a no-brainer to make a decision of what’s plausible.


Now, one could argue there are no "perfect experiments", and this doesn’t prove anything, and so on and so forth...

First objection: Let’s quit science – we can’t prove anything anymore – there are no perfect experiments.

Second objection: Yes, there are loopholes in Bell test experiments, as in any experiment. But there are different kind of loopholes, and different kind of performed experiments. The sum of performed experiments, all pointing in the same direction, is IMO much more convincing than current theoretical oppositions.​

Time will definitely tell – and I hope I’m free to have my own view in the meantime.

You are free to have yours.


As a dessert, it would be interesting if some of the pros could comment on this:

... The oft repeated statement that QM is incompatible with local hidden variables isn't quite true. QM is compatible with lhv formulations of certain setups, such as wrt the individual arms of optical Bell tests. QM is incompatible with lhv formulations of setups where the lhv is irrelevant wrt determining the results, such as wrt the correlations of joint results with some global measurement parameter.

 

[Frame Dragger]

I would add, Thomas, that a thread such as you describe exists... you were in it, and I believe you and DrChinese et al couldn't come to an agreement. If we're going to continue that discussion, lets, but starting from square one seems silly.

 

[Deepak Kapur]

ThomasT, pardon my French, but this reasoning doesn’t convince me in any way. I may be a layman, but I’m not stupid.

1) Quantum entanglement is a quantum mechanical state of a system of two or more objects.

2) It is generally accepted that there can be no interpretations of quantum mechanics which use local hidden variables.​

An atom is taken to be 99.9999... percent empty. Seeing from this viewpoint aren't all the actions 'actions at a distance'. Or the possibility of interacting particles for every kind of action is a certainity?

 

[DevilsAvocado]

An atom is taken to be 99.9999... percent empty.

Right, but it definitely depends on the selected 'perspective'. If we take the atom electron orbital; if measured as a particle, the 'voids' are huge. But if we think of the electron as a wave function, which is the preferred way without a measurement, the picture gets 'slightly' different:

[PLAIN]http://upload.wikimedia.org/wikipedia/en/thumb/e/e7/Hydrogen_Density_Plots.png/450px-Hydrogen_Density_Plots.png
The electron probability density for the first few hydrogen atom electron orbitals
shown as cross-sections, for the wave function of the electron.

Now, for the quarks inside nucleons, there’s a lot of 'space'. But according to recent discoveries in Quantum Chromodynamics (QCD) there are virtual particles, popping in and out, in the nucleon all the time:

[URL]http://www.physics.adelaide.edu.au/~dleinweb/VisualQCD/QCDvacuum/su3b600s24t36cool30actionHalf.gif[/URL]
And these virtual particles give 90% of the mass of atoms!

Therefore, when you say 99.9999% empty, it’s not the whole picture.

Seeing from this viewpoint aren't all the actions 'actions at a distance'.

Well, when grandmaster-spukhafte (Einstein) talked about "Spukhafte Fernwirkung" he meant spooky action at a distance, and the spooky part is – faster than the speed of light (FTL).

And all forces, inside and outside the atom, are propagated at (or below) the speed of light.

 

[Deepak Kapur]

Right, but it definitely depends on the selected 'perspective'. If we take the atom electron orbital; if measured as a particle, the 'voids' are huge. But if we think of the electron as a wave function, which is the preferred way without a measurement, the picture gets 'slightly' different:

[PLAIN]http://upload.wikimedia.org/wikipedia/en/thumb/e/e7/Hydrogen_Density_Plots.png/450px-Hydrogen_Density_Plots.png
The electron probability density for the first few hydrogen atom electron orbitals
shown as cross-sections, for the wave function of the electron.

Now, for the quarks inside nucleons, there’s a lot of 'space'. But according to recent discoveries in Quantum Chromodynamics (QCD) there are virtual particles, popping in and out, in the nucleon all the time:

[URL]http://www.physics.adelaide.edu.au/~dleinweb/VisualQCD/QCDvacuum/su3b600s24t36cool30actionHalf.gif[/URL]
And these virtual particles give 90% of the mass of atoms!

Therefore, when you say 99.9999% empty, it’s not the whole picture.


Well, when grandmaster-spukhafte (Einstein) talked about "Spukhafte Fernwirkung" he meant spooky action at a distance, and the spooky part is – faster than the speed of light (FTL).

And all forces, inside and outside the atom, are propagated at (or below) the speed of light.

Thanks for a very illustrative reply.

 

[DevilsAvocado]

You are welcome!

 

[ThomasT]

ThomasT, pardon my French, but this reasoning doesn’t convince me in any way. I may be a layman, but I’m not stupid.

1) Quantum entanglement is a quantum mechanical state of a system of two or more objects.

2) It is generally accepted that there can be no interpretations of quantum mechanics which use local hidden variables.​

I’m no expert; I just use 'common sense' to make up my mind of what is plausible (for the moment), and if I add Bell's theorem:

"No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics."​

To the fact that a lot of serious Bell test experiments have all indicated that Bell's theorem is accurate, and that not one has pointed clearly in the other direction; it’s a no-brainer to make a decision of what’s plausible.


Now, one could argue there are no "perfect experiments", and this doesn’t prove anything, and so on and so forth...

First objection: Let’s quit science – we can’t prove anything anymore – there are no perfect experiments.

Second objection: Yes, there are loopholes in Bell test experiments, as in any experiment. But there are different kind of loopholes, and different kind of performed experiments. The sum of performed experiments, all pointing in the same direction, is IMO much more convincing than current theoretical oppositions.​

Time will definitely tell – and I hope I’m free to have my own view in the meantime.

You are free to have yours.

Nice rant, but (1) I didn't say anything about Bell test loopholes, and (2) if there's some specific statement of mine that you disagree with, then please let us know exactly why you disagree with it.

There's no disagreement that the results of Bell tests agree with QM predictions, or that the results generally violate Bell inequalities. However, there's an ongoing debate regarding the physical meaning that should be given to these violations via the meaning given to the inequalities (and, similarly, to the detection attributes involved in GHZ inconsistencies).

Another consideration is that the application of Malus Law in Bell tests has a purely local basis.

It's important to keep in mind that the entanglement correlations in Bell tests have to do with the relationship between the entangled entities. This relationship isn't the same as the hidden variable. It's a hidden, constant parameter that's assumed (in the QM treatment as well) to have a local cause.

So when it's stated that no local hidden variable account of entanglement is possible, I agree -- but, this is simply due to the fact that the hidden variable(s) is irrelevant wrt the joint context correlations.

 

[ThomasT]

I would add, Thomas, that a thread such as you describe exists... you were in it, and I believe you and DrChinese et al couldn't come to an agreement. If we're going to continue that discussion, lets, but starting from square one seems silly.

That thread, ostensibly about the fair sampling loophole, went in a lot of directions. To get to an understanding of the physical meaning of BIs and GHZ it's necessary to start from 'square one'.

 

[Frame Dragger]

That thread, ostensibly about the fair sampling loophole, went in a lot of directions. To get to an understanding of the physical meaning of BIs and GHZ it's necessary to start from 'square one'.

Alright then, why not start a new thread? You're making the same argument with a slightly different audience, which may be why some of us are reacting poorly. I'm sure if you started a thread re: Malus' Law and the rest, you would probably have a more vigorous debate.

 

[ThomasT]

Alright then, why not start a new thread? You're making the same argument with a slightly different audience, which may be why some of us are reacting poorly. I'm sure if you started a thread re: Malus' Law and the rest, you would probably have a more vigorous debate.

Same argument as what?

 

[DevilsAvocado]

Nice rant

Thanks, you are much too friendly!

There's no disagreement that the results of Bell tests agree with QM predictions, or that the results generally violate Bell inequalities.

Great! Welcome to the spukhafte-gang! What’s the problem...??

However, there's an ongoing debate regarding the physical meaning that should be given to these violations via the meaning given to the inequalities

Ahhh, the physical meaning of things... I don’t want to spoil the familial atmosphere, but this question belongs in the Philosophical Section, don’t you think?

Another consideration is that the application of Malus Law in Bell tests has a purely local basis.

Bad math. Both you and I know that Malus Law is gone by the wind, when we use other particles.

It's important to keep in mind that the entanglement correlations in Bell tests have to do with the relationship between the entangled entities.

Okay, now we are talking!

This relationship isn't the same as the hidden variable. It's a hidden, constant parameter that's assumed (in the QM treatment as well) to have a local cause.

Yes, finally! Let’s discuss this:

You are saying – There are no Local Hidden Variables in QM, in QM there is Entanglement.
YES, I definitely agree!

You are saying – The QM Entanglement is local, hidden & constant.
Okay, you dismiss LHV, and 'replace' it with your version of QM entanglement that is local, hidden & constant...

How could this ever help your cause? If your version of entanglement is local and constant, it has even less probabilities to 'explain' what happens in Bell test experiments...??

Is it clear to you that the polarizing measuring apparatus can be rotated AFTER the photons left the source...?? ​

Conclusion: With a local *constant* in Bell test experiments you can’t do anything!

 

[Frame Dragger]

Same argument as what?

No response I could give to this would be appropriate on PF, so I will refrain.

Beyond that... I feel that DevilsAvocado now, and DrChinese before, have done a nice job of pointing out the errors in your personal beliefs.

 

[DevilsAvocado]

Thanks for the support Frame Dragger!

 

[RUTA]

But... even if we cannot use entanglement to send usable information FTL, the particles must clearly be 'communicating' in some way to present the opposite random property, right? And Bell showed there are no local hidden variables involved... or did I miss something?

MWI is the only 'way out' of this is, as I understand...?

There are other interpretations, as Frame Dragger points out in post #9 of this thread, to include the view where there are no particles (or any other quantum "entities") to communicate between one another in the first place. So, there are many ways people have devised to deal with "the greatest mystery in physics."

 

[Frame Dragger]

There are other interpretations, as Frame Dragger points out in post #9 of this thread, to include the view where there are no particles (or any other quantum "entities") to communicate between one another in the first place. So, there are many ways people have devised to deal with "the greatest mystery in physics."

Of course, as you aptly pointed out in another thread, the entire exercise of Interpretations is somewhat, if not entirely, fruitless. In fact, it can be distracting and the resulting agendas make life... difficult.

 

[RUTA]

Of course, as you aptly pointed out in another thread, the entire exercise of Interpretations is somewhat, if not entirely, fruitless. In fact, it can be distracting and the resulting agendas make life... difficult.

I'm sorry if I gave you that impression with something I wrote in another thread. In fact, I agree with Smolin (The Trouble with Physics, Houghton Mifflin, Boston, 2006) that the foundational problems of quantum mechanics probably constitute “the most serious problem facing modern science,” and this problem “is unlikely to be solved in isolation; instead, the solution will probably emerge as we make progress on the greater effort to unify physics.”

“In the past, fundamental new discoveries have led to changes – including theoretical, technological, and conceptual changes – that could not even be imagined when the discoveries were first made. The discovery that we live in a universe that, deep down, allows for Bell-like influences strikes me as just such a fundamental, important new discovery. … If I am right about this, then we are living in a period that is in many ways like that of the early 1600s. At that time, new discoveries, such as those involving Galileo and the telescope, eventually led to an entirely new way of thinking about the sort of universe we live in. Today, at the very least, the discovery of Bell-like influences forces us to give up the Newtonian view that the universe is entirely a mechanistic universe. And I suspect this is only the tip of the iceberg, and that this discovery, like those in the 1600s, will lead to a quite different view of the sort of universe in which we live.” Richard DeWitt, Worldviews: An Introduction to the History and Philosophy of Science, Blackwell Publishing, 2004, p 304.

 

[Frame Dragger]

I'm sorry if I gave you that impression with something I wrote in another thread. In fact, I agree with Smolin (The Trouble with Physics, Houghton Mifflin, Boston, 2006) that the foundational problems of quantum mechanics probably constitute “the most serious problem facing modern science,” and this problem “is unlikely to be solved in isolation; instead, the solution will probably emerge as we make progress on the greater effort to unify physics.”

“In the past, fundamental new discoveries have led to changes – including theoretical, technological, and conceptual changes – that could not even be imagined when the discoveries were first made. The discovery that we live in a universe that, deep down, allows for Bell-like influences strikes me as just such a fundamental, important new discovery. … If I am right about this, then we are living in a period that is in many ways like that of the early 1600s. At that time, new discoveries, such as those involving Galileo and the telescope, eventually led to an entirely new way of thinking about the sort of universe we live in. Today, at the very least, the discovery of Bell-like influences forces us to give up the Newtonian view that the universe is entirely a mechanistic universe. And I suspect this is only the tip of the iceberg, and that this discovery, like those in the 1600s, will lead to a quite different view of the sort of universe in which we live.” Richard DeWitt, Worldviews: An Introduction to the History and Philosophy of Science, Blackwell Publishing, 2004, p 304.

You do realize that everything you just said is in accord with the statement of mine you're disagreeing with? I'm saying that experiments, research, and theory are needed, not attempts at "Interpretations" of a theory that is clearly incomplete. I am, and have in the past here, argued for a semi-Instrumentalist approach, but with curiosity. I don't like the idea of these endless attemts to provide an ad hoc framework into which QM can be crammed.

I thought I made that clear in that other thread where I mentioned the need for an understanding of what occurs at and below the Planck Scale.

 

[DevilsAvocado]

... So, there are many ways people have devised to deal with "the greatest mystery in physics."

Agree. The important thing is maybe for now to accept that there are "grapes" out there that we can’t reach, but not act in absurdity to deny their existence.

And Smolin is very true.

Edit :) It’s very late here... I don’t know what I’m typing anymore... good night everybody...

 

[pallidin]

Interesting thread. Hard to grasp at times.

 

[zonde]

Are you saying that John Bell was totally wrong, and Alain Aspect was totally stupid spending all this time & money in experimentally verifying that Bell's inequalities are physically violated??

No, I am not saying that.
Derivation of Bell inequalities is mathematically sound. And how else you would find out to what extent mathematical construction is applicable to physical situation without performing experiments?

Anyways if we allow the possibility that unfair sampling is justified assumption then Aspect experiment demonstrates that photon ensembles can have QM type properties that individual photons can't have. And finding that out wouldn't seem like waste of time and money.

 

[DrChinese]

I would add, Thomas, that a thread such as you describe exists... you were in it, and I believe you and DrChinese et al couldn't come to an agreement. If we're going to continue that discussion, lets, but starting from square one seems silly.

I seem to remember twisting around on this for an extended period of time. I think I got dizzy in the end.



So I am not sure I can survive another round. To sum up some of my comments quickly:

Please think of Bell's Theorem as a roadmap rather than a Bible. Bell charted the way for us. Once he showed us the way, we can accomplish all kinds of things with entanglement - all of which are completely consistent with garden variety quantum mechanics.

If you try to analyze Bell semantically, you will miss the point entirely.

 

[RUTA]

You do realize that everything you just said is in accord with the statement of mine you're disagreeing with? I'm saying that experiments, research, and theory are needed, not attempts at "Interpretations" of a theory that is clearly incomplete. I am, and have in the past here, argued for a semi-Instrumentalist approach, but with curiosity. I don't like the idea of these endless attemts to provide an ad hoc framework into which QM can be crammed.

I thought I made that clear in that other thread where I mentioned the need for an understanding of what occurs at and below the Planck Scale.

Many in the foundations community believe attempts to interpret quantum physics are a good way to look for a theory to complete quantum physics. For example, what makes you believe there's something relevant to completing quantum physics "at and below the Planck Scale?" You must have some implicit metaphysical "interpretation" of quantum physics that suggests the importance of this scale.

 

[DevilsAvocado]

... Anyways if we allow the possibility that unfair sampling is justified assumption then Aspect experiment demonstrates that photon ensembles can have QM type properties that individual photons can't have. And finding that out wouldn't seem like waste of time and money.

With all due respect, this is almost an even worse insult to Alain Aspect...

Would a member of the French Academy of Sciences and French Academy of Technologies, and professor at the Ecole Polytechnique, awarded with 2010 Wolf Prize in physics, spend all this time & money to find out that the detection efficiency is always less than 100% in optical experiments...!?

A high school student can figure this out by asking his teacher...

This is not a sound debate. To me, it seems like a classical example of "not seeing the forest for the trees"... among some.
This is not a question whether we can trust physical experiments involving photons; it’s a much bigger question.


Let’s take a step back - To clarify the background
(for pallidin et al.)

Albert Einstein was not perfectly happy with the non-causal nature of the new quantum physics, and he had an ongoing debate with Niels Bohr about this matter. Both were Nobel Laureates in Physics, and considered the brightest minds of their time (and history!).

To keep it short: Einstein favored 'real' particles like photons – Bohr was only interested in the wave function, or to be precise, the equations describing wave function.

In 1935, Albert Einstein published a paper, known as the EPR paradox, with the title; "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?". So far Niels Bohr, almost in triumph, had dismantled every argument from Einstein swift and easy. But this time it was different, Bohr’s reply was published five months later (with the exact same title as the original), and the paper implied he had misinterpreted the profound analysis of Einstein.

According to Einstein the EPR experiment yields a dichotomy, either:

1) A quantum system has a non-local effect on the physical reality.
2) Quantum mechanics is incomplete in the sense that some extra variable is needed to account for it.​

In 1964, John Bell showed (theoretically) that quantum mechanics predicts much stronger statistical correlations between the measurement results, than the theory of hidden variable is ever capable of.

Bell's theorem proves that every quantum theory must violate either locality or counterfactual definiteness (i.e. Heisenberg uncertainty principle; one cannot simultaneously know the position and momentum of a particle).

To make things even more 'contradictory' – we know that quantum mechanics and the predictions of quantum field theory (QFT) are the most precise in all of physics!

John Bell knew that there where theoretical escape routes from his theorem, e.g. Superdeterminism in which we (and the particles) lose our free will by the predetermined laws of physics, and become 18th century Laplace's demons.

And as discussed here, there are other interpretations of QM, like Many-worlds (MWI) where we split the whole universe for every particle in EPR, etc.
​

Now, with this in mind, it seems almost silly with all this focus on photons!? The brightest minds in history knew that EPR was an important and profound aspect of quantum mechanics.

And we are discussing unfair or fair sampling assumption of photons??

Well, that approach to EPR is certainly unfair to all the effort that has been made by a lot of very intelligent people, in nearly a century.

But, as I mentioned earlier, there are different kind of Bell test experiments performed – and to quit the discussion about 'unfair sampling', once and for all, we can point out the fact that in 2001 M. Rowe et al. conducted an experiment that used detection methods that were almost 100% efficient, thus avoiding the 'unfair sampling loophole', using two trapped ions:

http://www.nature.com/nature/journal/v409/n6822/abs/409791a0.html"

Fair sampling is a reasonable assumption and is therefore not a loophole.

Time to rethink.

"It is difficult for me to believe that quantum mechanics, working very well for currently practical set-ups, will nevertheless fail badly with improvements in counter efficiency ..." -- J.S. Bell

 

[Frame Dragger]

Many in the foundations community believe attempts to interpret quantum physics are a good way to look for a theory to complete quantum physics. For example, what makes you believe there's something relevant to completing quantum physics "at and below the Planck Scale?" You must have some implicit metaphysical "interpretation" of quantum physics that suggests the importance of this scale.

You are diverting my point, by raising another. Tit for Tat RUTA... "A cat for a hat, or a hat for a cat, but nothing for nothing."

As for the rest, why do you feel I have a metaphysical interpretation? I don't see that as a logical conclusion from the standpoint of wanting to see the two major theories of physics AGREE (i.e. GR/QM). As for believing that interpeting QM will lead to breakthroughs... I'm yet to see that. It DOES provide people with something to say other than, "we don't know"... a notoriously bad phrase to place in a grant request. Please don't assume what I "must" or must not believe.

 

[DevilsAvocado]

the standpoint of wanting to see the two major theories of physics AGREE (i.e. GR/QM)

YES! That 'gang' is definitely on my supporter-list!

 

[Frame Dragger]

YES! That 'gang' is definitely on my supporter-list!

Heh, thanks DA. I always was under the impression that, while it seems to always be an elusive goal, that having these two amazingly useful and predictive theories NOT dovetailing is... unacceptable. Perhaps that would be my "metaphysical" reason for wanting to understand the Planck scale...

Btw, great last post!

 

[DevilsAvocado]

Heh, thanks DA. I always was under the impression that, while it seems to always be an elusive goal, that having these two amazingly useful and predictive theories NOT dovetailing is... unacceptable. Perhaps that would be my "metaphysical" reason for wanting to understand the Planck scale...

Well, as we all know – It takes two to tango!
And it’s not always that bad move your a*s around in space-time to see what we’ll find!

Btw, great last post!

Thanks!

 

[hmm.max]

I would add, Thomas, that a thread such as you describe exists... you were in it, and I believe you and DrChinese et al couldn't come to an agreement. If we're going to continue that discussion, lets, but starting from square one seems silly.

As a reader of this thread, I would personally rather that ThomasT wasn't discouraged from participating in the conversation. As someone trying to understand the current state of affairs with "hidden variable theories", his comments were the only part of this thread that peaked my interest, i.e. the only statements that I had not already come across numerous times on this forum already.

Obviously, everything in this thread has already been discussed elsewhere. It seems very strange to me to suddenly single out someone who is drawing a very subtle distinction, and tell them to stop, in the midst of advanced discourse such as

"Are you saying that John Bell was totally wrong, and Alain Aspect was totally stupid.."

Not trying to be inflammatory, I just mean that this thread doesn't seem so sacred that shutting someone up is warranted.

 

[zonde]

Now, with this in mind, it seems almost silly with all this focus on photons!? The brightest minds in history knew that EPR was an important and profound aspect of quantum mechanics.

And we are discussing unfair or fair sampling assumption of photons??

Well, that approach to EPR is certainly unfair to all the effort that has been made by a lot of very intelligent people, in nearly a century.

This is unfair in respect to Many-worlds interpretation, right?
MWI is so exciting and how can it be compared with something as dull as unfair sampling.
But bear in mind that success of QM is actually success of "shut up and calculate" interpretation and the closest interpretation to this approach is Ensemble interpretation.

But, as I mentioned earlier, there are different kind of Bell test experiments performed – and to quit the discussion about 'unfair sampling', once and for all, we can point out the fact that in 2001 M. Rowe et al. conducted an experiment that used detection methods that were almost 100% efficient, thus avoiding the 'unfair sampling loophole', using two trapped ions:

http://www.nature.com/nature/journal/v409/n6822/abs/409791a0.html"

To consider this experiment as an EPR paradox test is a bit of stretch. EPR paradox considers separate measurements of two systems that are not interacting at the moment of measurement. But in this experiment there is only one joined measurement of both systems.

Fair sampling is a reasonable assumption and is therefore not a loophole.

Yes, in most cases fair sampling assumption is considered reasonable. But in this case fair sampling assumption necessarily comes packaged with one of the not-so-reasonable speculations like MWI, superdeterminism or nonlocality of Pilot-wave.
And in that light fair sampling is as reasonable as most reasonable one of those alternatives.

Time to rethink.

As you say

"It is difficult for me to believe that quantum mechanics, working very well for currently practical set-ups, will nevertheless fail badly with improvements in counter efficiency ..." -- J.S. Bell

When Bell said that? Definitely it was quite some time ago. And still there is uncomfortable lack of experiments that explicitly test what happens when counter efficiency is changed above usual ~10% level even when there is constant improvement in photon detection technologies.

 

[DevilsAvocado]

Please hmm.max, you are commenting Frame Dragger, but quoting me...

I would personally rather that ThomasT wasn't discouraged from participating in the conversation.

I have never discouraged ThomasT from participating in the conversation, in fact the contrary:

Time will definitely tell – and I hope I’m free to have my own view in the meantime.
You are free to have yours.

As someone trying to understand the current state of affairs with "hidden variable theories", his comments were the only part of this thread that peaked my interest, i.e. the only statements that I had not already come across numerous times on this forum already.

I do think you have misinterpreted ThomasT, he does not support "hidden variable theories", but he replaces it with his own version of "entanglement" (as far as I understand):

It's important to keep in mind that the entanglement correlations in Bell tests have to do with the relationship between the entangled entities. This relationship isn't the same as the hidden variable. It's a hidden, constant parameter that's assumed (in the QM treatment as well) to have a local cause.

It seems very strange to me to suddenly single out someone who is drawing a very subtle distinction, and tell them to stop, in the midst of advanced discourse such as

"Are you saying that John Bell was totally wrong, and Alain Aspect was totally stupid.."

I’m afraid you’re mixing persons, quotes and arguments into an unrecognizable clutter. The quote above was from me addressed to zoned, and not to the very subtle drawings of ThomasT.

that shutting someone up is warranted.

Wrong, but I think Frame Dragger can speak for himself.

 

[DrChinese]

As a reader of this thread, I would personally rather that ThomasT wasn't discouraged from participating in the conversation. As someone trying to understand the current state of affairs with "hidden variable theories", his comments were the only part of this thread that peaked my interest, i.e. the only statements that I had not already come across numerous times on this forum already.

I don't think anyone is trying to shut anyone up, but to be fair some of the discussion with ThomasT has been had multiple times previously. I for one don't want to repeat the exact same debate with the same person.

On the other hand: if you are interested in discussing any element of EPR/Bell, I am sure we would all be interested.

 

[DrChinese]

Well, as we all know – It takes two to tango!
And it’s not always that bad move your a*s around in space-time to see what we’ll find!

Thanks!

Just adding to what was said already: you had some great posts above... good stuff.

 

[DrChinese]

I do think you have misinterpreted ThomasT, he does not support "hidden variable theories", but he replaces it with his own version of "entanglement" (as far as I understand):

ThomasT has indicated previously that there are definitional issues with entanglement. I don't see those particular ones and neither do most folks. So it gets hard to have a discussion because his vewpoint hinders that. There is a generally accepted common ground to discuss these issues, and that usually goes all the way back to EPR.