Is Quantum Entanglement Just Correlation or a Real Physical Process?

[zenith8]

It's meaningless to talk about observables before we measure them.

It's not about CI, it's about superposition of states.

Basic Logic:

(A) If you take an interpretation prepared to make a statement about what exists (e.g. the Bohm interpretation) then it is perfectly reasonable to talk about observables before we measure them.

(B) The Bohm interpretation uses precisely the same mathematics as the Copenhagen interpretation.

(A) + (B) --> It cannot be about superposition of states, it must be about CI.

 

[WaveJumper]

Basic Logic:

(A) If you take an interpretation prepared to make a statement about what exists (e.g. the Bohm interpretation) then it is perfectly reasonable to talk about observables before we measure them.

(B) The Bohm interpretation uses precisely the same mathematics as the Copenhagen interpretation.

(A) + (B) --> It cannot be about superposition of states, it must be about CI.

That's the whole point - you cannot pick ONE interpretation(e.g. the realistic MWI) and pull out an image of atoms and claim - Hey look, atoms are real!

Atoms are in superposition of states when they aren't observed/measured. What is the true nature of wavefunction is a subject of interpretaion and there are a multitude of them to suit all tastes(all of them untestable). You cannot base your logic on the validity of one of them, because they aren't falsifiable(i.e. circular logic). The hard data you have is an image, evidenced by an assumption(interpretation). Based on just these 2 you are not justified to claim with the certainty you did, that the atoms are real or not, which is what i objected to.

 

[zenith8]

That's the whole point - you cannot pick ONE interpretation(e.g. the realistic MWI) and pull out an image of atoms and claim - Hey look, atoms are real!

Again, not so. I wasn't talking about quantum interpretations in the post you are referring to - I was talking about experiments.

And as I keep saying, forget the image - that was just for fun. Read what I said in the text.

Atoms are in superposition of states when they aren't observed/measured. What is the true nature of wavefunction is a subject of interpretaion and there are a multitude of them to suit all tastes(all of them untestable).

You're completely missing the point. Because - in the matter-wave optics experiments - we find that it is possible to diffract, reflect, focus, interfere, do stimulated emission with the wave field in question (that is mathematically represented by the wave function) then that is experimental evidence for the objective existence of the wave. If the wave can be subject to and utilized in such a process, it logically follows that the wave field must exist in order to act and be acted upon.

You cannot base your logic on the validity of one of them, because they aren't falsifiable(i.e. circular logic).

I'm not basing my logic on the validity of one of them. You've just misunderstood (again):

We are trying to falsify your sweeping generalization that it is 'always meaningless to talk about observables before we measure them'. That is (because it's defined that way) a correct statement in the Copenhagen interpretation. It is an incorrect statement in the Bohm interpretation, where we make an ontological commitment as to what exists. Both interpretations are currently in complete accord with experiment. It is therefore not necessarily (and probably not, because it's bizarre) a correct statement in the real world, which is what we are talking about.

Therefore your statement is false.

because [interpretations] aren't falsifiable

That's probably because so many people have such a dogmatic insistence on this point that most don't bother looking how to falsify them. I know at least three possible experimental tests of the Bohm interpretation, for instance. Here's an interesting one I read the other day, due to P. Rigg (relevant to the current discussion):

An infinite potential well is an example of a situation that would offer different predictions for the same phenomenon by Copenhagen and Bohm. They do not give the same answer to the question of what a quantum particle with zero net intrinsic angular momentum is doing within the well. According to CI, it must be in motion, that is, measurements of the momentum would always give values bigger than some threshold (or the uncertainty principle would be violated). According to Bohm (let's not bother why), the particle has zero velocity. Is it possible to test this? Probably, yes:

Let's look at matter wave optics again, where suitable approximations to an infinite well are feasible. In the case of an atom trapped in such a cavity it is possible to ascertain the atom's trajectory by looking at how laser light leaving a cavity is modulated. If we only want to ascertain whether an atom is in motion or not then we can do measurements of the atom's momentum. Imagine a horizontal containment vessel (so that gravity will not affect the atom's motion along the length of the vessel) with evanescent light wave reflectors at each end (produced by a laser beam). The evanescent wave will reflect the atom if it is incident at the ends of the vessel without the atom touching the containment vessel's wall. Skipping the practical details, if the Bohm interpretation is correct, one would expect to detect no phase shift in the reflected laser light (i.e. no motion of the atom). If this proves not technically feasible, then one ought to be able to see phase shifts which consistently indicate values of momenta smaller than the minimum value predicted by orthodox QM. This experiment is very difficult, but probably not impossible to do.

I quote S. Manisalco:

"Quantum mechanics is a theory peppered with counterintuitive and bizarre aspects. For this reason, since its very early days, it has given rise to a heated debate - still far from being concluded - on its interpretation and consequences. ... During the last two decades, extraordinary experimental advances in the control and manipulation of single or small numbers of atoms have made it possible to realize experiments which have been considered for a long time as 'gedanken experiments and potentially test what was previously considered untestable."

I don't want this thread to turn into discussions of testing Bohm's interpretation (and I'm sure it won't), but I mention it merely so we understand that is not in principle impossible to distinguish between interpretations. A dogmatic insistence otherwise is just counterproductive.

21st century now, guys..

 

[zenith8]

Moved to Philosophy? How utterly ridiculous.

 

[zenith8]

Seriously, a lot of people have invested a lot of time in writing posts for this thread, and now some anonymous moderator feels he can just banish it to the Philosophy forum where no-one will read it, just on the basis of his personal prejudice that mention of the word 'interpretation' means 'philosophy'.

This thread is about Bell's theorem, non-locality, and action at a distance in quantum physics - these are topics worked on by a great many of the world's leading physicists, both experimental and theoretical. It is not, by any definition, philosophy.

Can the anonymous moderator who did this please post to justify his reasoning?

Thank you.
Zenith

 

[fleem]

So if you want a thread moved to philosophy, simply add a troll post and BOING its in the philosophy forum. My how kind of the moderators to give trolls such power!

 

[zenith8]

So if you want a thread moved to philosophy, simply add a troll post and BOING its in the philosophy forum. My how kind of the moderators to give trolls such power!

Where's the troll post?

If you're referring to the experiment I suggested at the end of my last technical post - then it is a real experiment suggested in a peer-reviewed journal - see p. 3072 of the article "Quantum phenomena in terms of energy-momentum transfer" in J. Phys. A: Math. Gen. 32, 3069 (1999) and many subsequent follow-ups.

See also "Manipulating atoms with photons", Cohen-Tannoudji and Dalibard in "The new physics of the 21st century" ed. G Fraser, Cambridge University Press (2005).

 

[fleem]

Where's the troll post?

If you're referring to the experiment I suggested at the end of my last technical post - then it is a real experiment suggested in a peer-reviewed journal - see p. 3072 of the article "Quantum phenomena in terms of energy-momentum transfer" in J. Phys. A: Math. Gen. 32, 3069 (1999) and many subsequent follow-ups.

See also "Manipulating atoms with photons", Cohen-Tannoudji and Dalibard in "The new physics of the 21st century" ed. G Fraser, Cambridge University Press (2005).

My point is that even if a moderator believes some posts are philosophizing, the moderator should still be hesitant to move the thread to the philosophy forum, because otherwise trolls can easily manipulate the forums. This point is important because it proves the mistake of moving this thread to philosophy without having to debate how much philosophizing was actually occurring within this thread (since surely no one believes it was excessive... I hope). Certainly a thread with obvious excessive philosophizing and little or no science, should be moved. That wasn't the case here.

 

[zenith8]

My point is that even if a moderator believes some posts are philosophizing, the moderator should still be hesitant to move the thread to the philosophy forum, because otherwise trolls can easily manipulate the forums. This point is important because it proves the mistake of moving this thread to philosophy without having to debate how much philosophizing was actually occurring within this thread (since surely no one believes it was excessive... I hope). Certainly a thread with obvious excessive philosophizing and little or no science, should be moved. That wasn't the case here.

I agree completely. So how come a thread with little or no philosophizing and no trolls has ended up here? Someone has made a mistake. Can it be rectified please?

 

[ajw1]

This is incredible! How to discourage an interesting discussion.

Please moderators, reevaluate this action.

 

[WaveJumper]

You're completely missing the point. Because - in the matter-wave optics experiments - we find that it is possible to diffract, reflect, focus, interfere, do stimulated emission with the wave field in question (that is mathematically represented by the wave function) then that is experimental evidence for the objective existence of the wave. If the wave can be subject to and utilized in such a process, it logically follows that the wave field must exist in order to act and be acted upon.

Yes, i concede that it appears you are right. The problem with the cat(or should i say cats) re-surfaces and is back in full swing.

 

[zenith8]

Yes, i concede that it appears you are right. The problem with the cat(or should i say cats) re-surfaces and is back in full swing.

No, it isn't. If - as you say - you now accept that the wave exists, and you (just temporarily) grant me some license with my experimental evidence that particles exist (remember particles are all you actually detect in, say, a two-slit experiment with electrons), then one resolves the cat paradox as follows:

The cat is made of particles. There is also an accompanying objectively existing wave field (represented mathematically by the wave function evolving according to the Schroedinger equation). The wave guides the particles along particular trajectories according to the standard de Broglie-Bohm prescription. The wave - for whatever reason - splits up into non-overlapping branches, which (by decoherence arguments for a macroscopic body) can effectively never overlap again. The particles - which cannot pass through nodes in the many-body wave field - just deterministically end up in one of the branches (which one depends on the particular initial conditions, with a probability that depends on the fraction of initial trajectories that end up in a particular branch).

Thus the particles effectively select one of the branches to be the one that actually happens. This saves us from having to say that each branch forms a whole separate new universe, or (and this is really funny) when we look at the cat the wave suddenly decides to stop evolving according to the Schroedinger equation and er.. instantaneously collapses to a point - no matter how widely distributed over the universe it is - then starts evolving according to the Schroedinger equation again (as implied in orthodox QM).. In the Bohm picture the 'empty waves' just disperse and eventually become part of the background noise.

Simple, isn't it?

P.S. Can we invite you to join our protest in ending up in the Philosophy forum?

 

[pallidin]

Very interesting thread! At the very least, the way this thread evolved should take it out of the Philosophy section of PF.
Just my opinion.

 

[ThomasT]

I assume you mean that no proven physical process has been found for the nonlocal effects and the 'spooky action at a distance'.

I mean that "spooky action at a distance" exists solely as a speculative metaphysical explanation for quantum entanglement correlations.

'Nonlocal effects' regarding any given pair of detection attributes are inferred only when joint filter settings are parallel or perpendicular. But nonlocal effects or actions at a distance aren't necessary to understand why these joint settings produce the results that they do.

At joint settings other than parallel or perpendicular, individual detections at both ends remain random.

In my opinion if one accepts that the Bell experiment supports the standard QM interpretation then both 'Nonlocality' as well as 'spooky action at a distance' have been proven experimentally. For me these words refer to the same process that is called 'collapse of wave function forcing entangled particles to take a stand' in classic QM. In this sense 'spooky action at a distance' is also just a name, no explanation at al.

Afaik, standard QM doesn't use 'collapse of the wavefunction' to refer to speculative occurances in the quantum realm underlying instrumental behavior. It refers to changes in the objective experimental situation following qualitative instrumental results.

The objective situation is what has been instrumentally recorded -- and as far as the objective situation is concerned, neither ftl propagations nor actions at a distance have been demonstrated in entanglement experiments.

I think the important conclusion is that one should not suggest that this problem has been solved, as some of the earliest posts in this topic did. It is only solved by ignoring ontological questions or taking one of the (unproved) interpretations for granted.

Nonlocality, like any metaphysical speculation, is only a consideration if one assumes that the possibility of its existence is well supported. In my view, it isn't.

The point of departure for speculations on the existence of nonlocality is a certain take on the meaning of Bell's theorem. If, as has been suggested, Bell's theorem doesn't pertain to nonlocality, then what other reason is there to entertain the possibility of its existence?

 

[ThomasT]

So you're a fundamentalist instrumentalist (far too many syllables for a job description).

It has a nice ring to it, however I believe in and like to speculate about the deeper reality underlying instrumental behavior. While science is limited to the sensory realm, instrumental behavior provides the basis for many good assumptions about deeper reality which might then become the basis for more realistic theories.

... I fail to see why you are using the instrumentalist Orthodox interpretation of QM to make sweeping statements about the physical reality of 'action at a distance', and to justify writing 'Incorrect. Incorrect.' next to perfectly correct statements of fact in my original post #36.

The assumption of nonlocality in nature isn't warranted vis standard qm -- and the passage from the Stanford Encyclopedia of Philosophy (concerning standard qm) that you quoted supports this.

Note that in post #77 of this thread I retracted my statement that quantum nonlocality is acausal. It's causal, but nonlocality isn't part of or implied by standard qm.

Here's the argument against the assumption of nonlocality:

Statistical dependence of the separate data sets is what causes violation of Bell inequalities. The statistical dependence has a local causal explanation vis experimental design and execution.

Hence, as I outlined in post #77, violation of Bell inequalities does not require superluminal causal connections, nor does it require superluminal info transmission.

Where does this leave us wrt nonlocality? It's an open question, of sorts. But there's no 'nonlocality problem' because there's no good reason to assume that nonlocality is a realistic possibility.

I agree with you that physics can benefit from exploring inferences about the deeper reality. However, I don't think that the existence of a deeper wave and particle reality implies nonlocality. Our universe might be local or nonlocal. I think it's, presently, more reasonable to suppose that there's a propagational speed limit equivalent to the speed of light.

The main difference of opinion seems to be that you think that 'realistic' means 'engaging in speculative metaphysics' rather than 'objectively existing' ...

There are levels of reality. Our mode of existence is somewhat limiting. We all agree that there's a deeper reality. When we offer qualitative descriptions of that deeper reality, then we're engaging in speculative metaphysics because there's no way to completely objectify the descriptions themselves. The only things that are amenable to objectification are the instrumental behaviors predicted by the quantitative theory.

... and that 'metaphysics' appears to be some sort of term of abuse.

It is, somewhat. Speculative physics involves formulating testable hypotheses. Metaphysical speculations are, by definition, nontestable -- though they can still be evaluated as more or less reasonable.

Anyway, it seems that a certain amount of metaphysical speculation will always be part of theoretical physics -- and both despite and because of this, physics will continue to progress.

We cannot accept, as a legitimate argument form, inferences from the unobservability of a distinction to the unreality of the distinction.

FAPP we can. If the level of reality wrt which objective distinctions are made (instrumental predictions) produces no distinction, then as far as the science is concerned there's no distinction.

It's mostly just a matter of taste as to which of several competing nonverifiable descriptions of deep reality is adopted. I say mostly, because some metaphysical speculations are more reasonable than others.

Given what we know, the assumption that our universe is local is the more reasonable alternative.

 

[fleem]

We find nothing spooky about a pair of local particles transferring information (energy, particles, virtual photons) without regard to causality because we consider such interactions as occurring instantaneously, and we learned from the classical world that where there is no time there is no "sequence of events", and where there is no sequence of events there is no causality. In studying entanglement we've discovered the exact same thing can apply to particles that we presume through classical laws are some distance apart from each other, as long as we do not attempt to measure the space-time interval between them. Specifically, it can happen as long as there are no events at each end of that presumed space-time interval. So this should lead us to realize that a space-time interval doesn't exist unless there are events at each end. Specifically, it is those events that define the space-time we're so used to measuring classically (macroscopically).

 

[ThomasT]

As for this particular thread being moved to the (general) Philosophy forum, I don't care. The issues of nonlocality and spooky action at a distance involve certain experimental techniques, results, etc., as well as logical analysis. Sorting it all out is doing philosophy, but it's also an integral part of the whole scientific enterprise.

It's a coin flip. In the absence of some compelling reason to stick it in the Philosophy forum, why not just leave it where it was?

I think it might be a good idea to consider adding a few new sub-forums. Foundational and other, more or less philosophical, issues surrounding quantum theory could branch from the Quantum Physics forum.

 

[ThomasT]

We find nothing spooky about a pair of local particles transferring information (energy, particles, virtual photons) without regard to causality because we consider such interactions as occurring instantaneously, and we learned from the classical world that where there is no time there is no "sequence of events", and where there is no sequence of events there is no causality. In studying entanglement we've discovered the exact same thing can apply to particles that we presume through classical laws are some distance apart from each other, as long as we do not attempt to measure the space-time interval between them. Specifically, it can happen as long as there are no events at each end of that presumed space-time interval. So this should lead us to realize that a space-time interval doesn't exist unless there are events at each end. Specifically, it is those events that define the space-time we're so used to measuring classically (macroscopically).

I don't understand what you're saying here.

 

[fleem]

I don't understand what you're saying here.

We learned about space-time by observing the average behavior of many interacting particles. Specifically, we created the idea of space-time to explain the average behavior of particles. A theory designed solely to explain the average behavior of many simple machines, without any regard whatsoever to the behavior of one of those machines, will not likely be very useful in explaining the behavior of a single machine. It will far more likely prevent us from understanding the machine. Space-time is a strictly classical theory. In fact, even the idea of continuums and manifolds is a strictly classical theory in the same way. Yet scientists the world round continue to blindly presume that the very concepts we designed strictly to predict the average behavior of many particle interactions must unequivocally be used as the foundational axioms in a theory designed to predict the behavior of just one of those interactions. Its rather silly when you think about it.

 

[Doc Al]

Moderator's Note: I'm returning this thread to Quantum Physics, with the proviso that the discussion remain focused on the physics. I think there's some good physics being discussed and that the discussion should continue as long as it doesn't drift off course.

- Doc

 

[ajw1]

The statistical dependence has a local causal explanation vis experimental design and execution.

This seems to be the heart of our difference in opinion. If this would be correct the results of the experiment could not be used to support the predictions made by orthodox QM. Furthermore there would be no reason for all the hard work done by http://www.physorg.com/pdf132830327.pdf" .

A local causal explanation is a local hidden variable explanation. Of course de Bell experiments might have flaws, but the common view is that hidden variables are excluded by the experiment.

 

[zenith8]

This seems to be the heart of our difference in opinion. If this would be correct the results of the experiment could not be used to support the predictions made by orthodox QM. Furthermore there would be no reason for all the hard work done by http://www.physorg.com/pdf132830327.pdf" .

A local causal explanation is a local hidden variable explanation. Of course de Bell experiments might have flaws, but the common view is that hidden variables are excluded by the experiment.

You're quite right - apart from the fact that only local hidden variables are considered to be excluded by experiment; non-local hidden variables (as in the Bohm theory) are not.

It is not clear to me either why ThomasT appears to think the results of Bell-type experiments have a perfectly simply local hidden variable explanation. It is the whole point of the thing that it does not.

 

[ajw1]

If we accept for now that the Bell experiment isn't flawed and the data from the experiments suggest that some FTL action appears to happen, are there any experiments that support one of the ontological interpretations mentioned in this topic?

"Perhaps the most convincing proof of the reality of the quantum world would be to capture some of its creatures and hold them in place for all to see. This has become feasible." [Ho-Kim et al., 2004]

Clear evidence for the existence of the wave field (which is mathematically represented by the wave function) comes from the modern development of matter wave optics. In ultracold atomic gases the speed of the atoms is so slow that the de Broglie wavelength of an atom is approximately equal to the spacing between individual atoms. The atoms then have a dominant wave behaviour that allows manipulation by laboratory atom-optical devices. Although the matter wave (i.e. wave field) is not directly observable, the fact that significant quantities of matter can be diffracted, focussed, reflected, etc using essentially optical devices is clear evidence that wave fields are physically real.

Also 'matter wave amplification' experiments give further evidence for the existence of wave fields i.e. production of an output of atoms with particular properties from a Bose-Einstein condensate reservoir of atoms in a trap using a process similar to stimulated emission of light in a laser. If the wave can be subject to and utilized in such a process, it logically follows that the wave field must exist in order to act and be acted upon.

Maybe a bit off-track, but very interesting: If the experiments suggests the De Broglie waves are real, are there any theories/indications about what might be waving?

p.s. Do you recommend Quantum Causality from Peter Riggs for futher reading? Looks interesting to me.

 

[zenith8]

If we accept for now that the Bell experiment isn't flawed and the data from the experiments suggest that some FTL action appears to happen, are there any experiments that support one of the ontological interpretations mentioned in this topic?

See Valentini's work cited in my post #51 in this thread, as well as Riggs's book that you mention.

Maybe a bit off-tack, but very interesting: If the experiments suggests the De Broglie waves are real, are there any theories/indications about what might be waving?

You're not allowed to ask that question in electromagnetism either! It is the wave field (mathematically represented by the wave function) that is waving. What it actually is - hmm...

p.s. Do you recommend Quantum Causality from Peter Riggs for futher reading? Looks interesting to me.

I read that book a few weeks back - I recommend it wholeheartedly for those who wish to understand the viewpoint I have espoused in this thread.

On the specific topic of nonlocality - as already mentioned - I recommend Tim Maudlin's "https://www.amazon.com/dp/0631232214/?tag=pfamazon01-20 from Cambridge also gives an interesting perspective on this.

 

[ThomasT]

The statistical dependence has a local causal explanation vis experimental design and execution.

This seems to be the heart of our difference in opinion.

It's part of it. The point is that, in the absence of a certain interpretation of the meaning of violations of Bell inequalities, the design, execution, and standard qm models of quantum entanglement experiments don't exclude, and even suggest, that the correlations are the result of causal interactions and transmissions constrained by c.

So, the assumption of nonlocality rests on the interpretation of the meaning of Bell's lhv ansatz. The "crucial assumption" is, according to Bell, nonlocality (ie., causal independence of spacelike separated events at A and B) which is represented in the formulation by the factorability of the joint statistical probability.

However, A and B can be causally independent while still being statistically dependent if outcomes at one end affect the sample spaces at the other end vis the pairing process. Since the sample spaces and outcomes at A and B are in fact interdependent, and the separate data sets therefore statistically dependent, then factorability by itself isn't sufficient to represent locality -- and Bell's 'locality condition' isn't a locality condition but rather just a statistical independence condition.

If this is correct, then we can infer that:

(1) experimental violation of Bell inequalities doesn't imply the existence of nonlocality or ftl transmissions in Nature.

(2) nonfactorability or nonseparability of the standard qm representation of entangled states doesn't mean or imply nonlocality.

 

[StandardsGuy]

sokrates,
I guess their idea is that the wave function is some kind of material "fluid", that superposition of states is a real thing, and that wavefunction's collapse is an objective physical process.

The definition in the link to wave function is: "A wave function is a mathematical function that describes a physical system in quantum mechanics. The time evolution of this wave function, and thus, the system itself is described by the Schrödinger Equation."

Emphasis is mine. What is the "Time evolution"? Is it instantaneous or not?

 

[ThomasT]

If this would be correct the results of the experiment could not be used to support the predictions made by orthodox QM.

Why not? QM accurately predicts the outcomes of Bell experiments no matter how Bell is interpreted.

Furthermore there would be no reason for all the hard work done by http://www.physorg.com/pdf132830327.pdf" .

“The significance of our experiment lies entirely in achieving space-like separation, even under the assumption that a quantum measurement is only finished after a macroscopic mass has moved, as in the Penrose-Diosi model,” Zbinden explained.

Bell experiments usually advance the state of the art. They're valuable for that reason alone.

A local causal explanation is a local hidden variable explanation.

An intuitive understanding of the statistical dependencies and the correlations as being locally caused, which is what we have without the inference of nonlocality vis Bell, isn't quite the same as a local hidden variable explanation.

Of course de Bell experiments might have flaws, but the common view is that hidden variables are excluded by the experiment.

The lhv formulation on which experimentally violated inequalities are based is incompatible with the experimental designs which produce entanglement. The incompatibility has to do with the locality condition which is, sufficiently, a statistical independence condition.

Bell's analysis doesn't exclude lhv formulations. Lhv formulations are compatible with qm wrt the prediction of individual detections (the rates are predictable, the sequences are random). The CI goes a bit deeper in saying that, assuming locality, hidden variable descriptions are excluded due to foundational principles of quantum theory which emerge from the assumption of the existence of a fundamental quantum of action.

Interestingly, wrt Bell experiments the hidden variables determining individual detection are irrelevant. Knowing the exact qualitative properties of the separately measured quanta wouldn't alter the joint probabilities, because the joint probabilities depend only on assumptions (based on local causality) already embodied in the standard qm models. That is, it's only the relationship between the separately measured quanta that matters.

 

[ajw1]

Why not? QM accurately predicts the outcomes of Bell experiments no matter how Bell is interpreted.

Yes, but it wouldn't say anything conclusive between orthodox QM interpretation and any local hidden variable theory

“The significance of our experiment lies entirely in achieving space-like separation, even under the assumption that a quantum measurement is only finished after a macroscopic mass has moved, as in the Penrose-Diosi model,” Zbinden explained.

Bell experiments usually advance the state of the art. They're valuable for that reason alone.

The referenced article also contains the quote
"Altogether, the experiment serves to fill a loophole by ruling out any kind of communication between two entangled particles separated by a distance, provided the collapse happens only after a mass has moved. By spatially separating the entangled photons, the test once again confirms the nonlocal nature of quantum correlations."

An intuitive understanding of the statistical dependencies and the correlations as being locally caused, which is what we have without the inference of nonlocality vis Bell, isn't quite the same as a local hidden variable explanation.

The lhv formulation on which experimentally violated inequalities are based is incompatible with the experimental designs which produce entanglement. The incompatibility has to do with the locality condition which is, sufficiently, a statistical independence condition.

Bell's analysis doesn't exclude lhv formulations. Lhv formulations are compatible with qm wrt the prediction of individual detections (the rates are predictable, the sequences are random). The CI goes a bit deeper in saying that, assuming locality, hidden variable descriptions are excluded due to foundational principles of quantum theory which emerge from the assumption of the existence of a fundamental quantum of action.

Interestingly, wrt Bell experiments the hidden variables determining individual detection are irrelevant. Knowing the exact qualitative properties of the separately measured quanta wouldn't alter the joint probabilities, because the joint probabilities depend only on assumptions (based on local causality) already embodied in the standard qm models. That is, it's only the relationship between the separately measured quanta that matters.

Without any raw data from the experimental setup and results I consider myself incapable of conclusively judge the statistical results of Bell experiments, so you might be right. The thing is that people actually working with these kinds of experiments seem to conclude otherwise.

 

[RUTA]

An intuitive understanding of the statistical dependencies and the correlations as being locally caused, which is what we have without the inference of nonlocality vis Bell, isn't quite the same as a local hidden variable explanation.

Are you pointing out the distinction between separability and locality a la Howard?

Separability principle: any two systems A and B, regardless of the history of their interactions, separated by a non-null spatio-temporal interval have their own independent real states such that the joint state is completely determined by the independent states.

Locality principle: any two spacelike separated systems A and B are such that the separate real state of A let us say, cannot be influenced by events in the neighborhood of B.

D. Howard in Potentiality, Entanglement and Passion-at-Distance, R.S. Cohen et. al. (eds.), (Kluwer Academic Publishers, London, 1997), pp. 124-125.

 

[RUTA]

Without any raw data from the experimental setup and results I consider myself incapable of conclusively judge the statistical results of Bell experiments, so you might be right. The thing is that people actually working with these kinds of experiments seem to conclude otherwise.

If you'd like to see some data in these types of experiments, check out Table 1 in:

"Entangled photons, nonlocality, and Bell inequalities in the undergraduate laboratory," D. Dehlinger & M.W. Mitchell, Am. J. Phys. 70, Sep 2002, 903-910.

 

[ThomasT]

Are you pointing out the distinction between separability and locality a la Howard?

No. I'm just saying that there's a difference between an intuitive understanding of the statistical dependencies and correlations as being solely due to interactions and transmissions constrained by c, and a formal lhv model.

A real contradiction between our intuitive local causal view and standard qm hasn't been definitively established.

 

[pallidin]

No. I'm just saying that there's a difference between an intuitive understanding of the statistical dependencies and correlations as being solely due to interactions and transmissions constrained by c, and a formal lhv model.

A real contradiction between our intuitive local causal view and standard qm hasn't been definitively established.

Now, that's a serious statement! Nice job!

 

[john 8]

Play UK stated;
Coming at this problem from the angle of philosophy/psychology and an unhealthy relationship with the Journal of Consciousness Studies, I'm interested to know how you Physicists interpret the process of collapse, or rather the concept of entanglement. I've read so much new age rubbish all over the place (although I wouldn't call Penrose or Evin Harris Walker new-ager's). Does the violation of Bell's Inequalities demonstrate that quantum "spooky action at a distance" is not merely correlation, but some real physical process? Is this only the case if you try to interpret QM in local realistic terms?

I suppose what I really want to know is how does photon A "connect with" photon B, such that a measurement on A instantaneously acts on B? Is there no fact of the matter at the moment, or is it all down to your particular flavour of philosophical interpretation?



You replied;

PlayUK, Welcome to PF...

Murray Gell-Mann gives an analogy I like a lot when interpreting "spooky action at a distance":

Professor X has a peculiar habit, he puts on a BLUE sock and a RED sock every day instead of wearing identical pairs like normal people. The foot he chooses to put on these socks, however, is random. Therefore one day he could put on a blue sock on his right foot,but the other day he could do just the opposite. You, as the observant student, cannot know which color will end up in which foot before seeing one of his feet (and no complicated theory will help you predict that because it's really random), but once you see one of his socks, you immediately know the color of the sock you didn't see. There's no mechanism, no spooky action at a distance, when you see the the blue sock, you KNOW where the red sock is.

This is Gell-Mann's interpretation (I think it's originally attributed to someone else but I can't remember it now) and could be found in his book "The Quark and the Jaguar" . So if anybody is going to attack this with their own view on the subject, MGM is the man to talk to.

But I have a feeling his interpretation would be far more convincing than any other that I'll ever see in this forum.

Alright, time to take a look at your example. First let's give a quick and simple definition of this “spooky action at a distance” aka, quantum entanglement.

This action refers to the interaction of two objects which are separated by a distance, any distance, and this interaction occurs instantaneously and with no known physical connection or medium.

So one object does one thing and instantly another object responds to this action.

Now in your example one sock does not change the color of the other sock. In fact nothing changes, both socks remain the same color as they were when professor X put his socks on in the morning.

Like you said there is no “spooky action at a distance” between objects. So I would like to know what your point is in presenting this example. Has the phenomena of quantum entanglement been explained in the above example? Did you answer Play Uk's question?

If so I just do not see how.

What are we to be convinced of?

 

[Nick666]

I suppose what I really want to know is how does photon A "connect with" photon B,

They are one and the same ?

 

[ajw1]

No. I'm just saying that there's a difference between an intuitive understanding of the statistical dependencies and correlations as being solely due to interactions and transmissions constrained by c, and a formal lhv model.

A real contradiction between our intuitive local causal view and standard qm hasn't been definitively established.

Now, that's a serious statement! Nice job!

How is that a nice job? I haven't seen any evidence for this statement so far. And again: articles on this subject all confirm the nonlocal behaviour for entangled particles.

@ThomasT, do you have any reference supporting your statement?

 

[zenith8]

Now, that's a serious statement! Nice job!

Hi Pallidin,

OK just to check you have understood ThomasT's idea (and to help slow people like me) here's an exercise for you:

Can you re-explain ThomasT's statement to us - using different words to him as far as you can - and tell us why you think it might be true? (Imagine we're all idiots if it'll help).

Cheers,
Zenith

 

[WaveJumper]

Hi Pallidin,

OK just to check you have understood ThomasT's idea (and to help slow people like me) here's an exercise for you:

Can you re-explain ThomasT's statement to us - using different words to him as far as you can - and tell us why you think it might be true? (Imagine we're all idiots if it'll help).

Cheers,
Zenith

I thought Pallidin was disagreeing with ThomasT's statement.

Anyway, i keep on thinking that we've reached a time when we have to embrace the idea that our inherent classical logic and reasoning of spatial differentation is not a proper picture of how the universe is, in trying to understand how non-local effects can manifest in a local universe. Pretty mind-bending but i suppose that's how if was when the Earth was declared round.

 

[zenith8]

I thought Pallidin was disagreeing with ThomasT's statement.

In which case he's being damned subtle about it. Too subtle for the likes of me at any rate.

Anyway, i keep on thinking that we've reached a time when we have to embrace the idea that our inherent classical logic and reasoning of spatial differentation is not a proper picture of how the universe is, in trying to understand how non-local effects can manifest in a local universe. Pretty mind-bending but i suppose that's how if was when the Earth was declared round.

You sound just about ready for Bohm's concepts of implicate and explicate orders then.. (Look it up!)

 

[pallidin]

All I was doing was expressing an appreciation for someone making bold assertions.
From those assertions comes eventual clarification or outright rebuttal.

I love it! People taking an actual position, right or wrong.

I recall something in my studies which, to paraphrase, says "I would that thou were either hot or cold, but because thou art lukewarm I will spew thee out of my mouth."

I learn a lot from this! Bold assertions! That's why I "pushed" his comment.

 

[ThomasT]

How is that a nice job? I haven't seen any evidence for this statement so far. And again: articles on this subject all confirm the nonlocal behaviour for entangled particles.

@ThomasT, do you have any reference supporting your statement?

I at first thought that pallidin was being facetious. But on reading his last post, maybe not. In any case, there's nothing particularly bold about my assertions (or conjectures).

I thought that the pre-Bell or sans-Bell mainstream view was a local causal one.

The historical development of qm, the design and execution of entanglement experiments, and the similarity between the angular dependencies produced in archetypal A-B optical Bell tests and polarimetric setups are all compatible with a local causal view.

Optical disturbances between crossed polarizers don't produce a linear correlation between the angular difference and the resultant intensity. The situation with two, presumably identical, opposite-moving quantum optical disturbances is essentially the same. The correlation between the angular difference and the joint detection rate isn't linear, but follows, ideally, the Law of Malus.

keep in mind that it's the relationship between separated disturbances that's being measured by a global parameter. This relationship is itself a global parameter. Is it so surprising that measuring the same thing with the same devices and the same (or opposite) settings produces predictable results, and even accurate conditional predictions wrt individual detections?

Nonseparability of the joint state in standard qm doesn't by itself imply nonlocality -- quantum entanglement experiments are designed to produce the observed statistical dependencies via local interactions and transmissions. The qm treatment contains all the necessary info. The values of the hidden variables that determine individual detections are irrelevant.

Bell's theorem and Bell inequalities are, afaik, the sole basis for inferring nonlocality.

The inference of nonlocality has to do with the representation of locality. The locality condition is the separability of the joint state. An lhv representation requires this. However, separability excludes statistical dependence (the interdependence of detection events at one end and sample spaces at the other end) as well as nonlocality.

So, violation of inequalities based on this locality condition might be due to nonlocal interactions and transmissions, or they might be due to statistical dependence, which we can understand vis local causality -- and, therefore, the existence of nonlocality hasn't been conclusively demonstrated.

There are as well other reasons to believe that we inhabit a locally causal universe. So, it's an assumption that's not easily abandoned. The meaning of Bell's theorem and violations of the inequalities have been approached in different ways. Maybe it's gotten more complicated than necessary. Another reason why some physicists think that there's no definitive word on the existence of nonlocality has to do with the inability to close all of the loopholes in a single experiment. But (if that's still the case) that's another discussion.

 

[ajw1]

keep in mind that it's the relationship between separated disturbances that's being measured by a global parameter. This relationship is itself a global parameter. Is it so surprising that measuring the same thing with the same devices and the same (or opposite) settings produces predictable results, and even accurate conditional predictions wrt individual detections?

Of course it's no surprise that the Bell experiment produces correlated results for the combined measurements. The astonishment of the scientific world was that Bell showed that the statistic results would be different when the particles measured would have effected each other at the time of measurement or when it was just about particles with opposite properties.

 

[zenith8]

All I was doing was expressing an appreciation for someone making bold assertions. From those assertions comes eventual clarification or outright rebuttal.

I love it! People taking an actual position, right or wrong.

The planet Pluto is made of toffee ice cream!

(the exclamation marks make it a bold assertion).

I repeat, do you actually understand what ThomasT is saying, or is this just like picking a sports team and whooping when you think they've scored a goal? It's OK if you don't understand him - we won't judge you. I'm just interested..

 

[ThomasT]

Of course it's no surprise that the Bell experiment produces correlated results for the combined measurements. The astonishment of the scientific world was that Bell showed that the statistic results would be different when the particles measured would have effected each other at the time of measurement ...

Why is that astonishing? A successful causal, hidden variable, joint state representation requires that the individual results, by themselves, be predictable (for a local model) -- or that nonlocal interactions be assumed (for a nonlocal model).

... or when it was just about particles with opposite properties.

I'm not sure what you mean by this.

 

[ajw1]

Maybe this will help clearing things up: can you please describe where exactly you think this author "[URL Wiki[/URL] goes wrong (and please use external references if possible that support your vision)?

In contrast, Bell's theorem places a straight-line limit on the curve that any local hidden variable model (involving identical particles) can follow from correlated to anti-correlated. The QM prediction for entangled particles breaks this limit. For example, when the relative analyzer alignment is 22.5 degrees QM gives 0.71 correlation whereas the straight-line limit (implied by Bell's theorem) is 0.5. From this, one may conclude that the outcome of Quantum measurements on entangled particles cannot be replicated by a model that employs identical particles that have hidden attributes/properties which locally determine the outcome of measurements.

One possible way for a hidden variable system to break the limit imposed by Bell's theorem, is to suppose that some non-local process or communication acts to increase the degree of correlation above the limits imposed by Bell's theorem. To test this possibility, the analyzer angles are set at arbitrary angles before measuring the particles, even after the particles leave the source. In this case, this supposed non-local interaction or communication would have to occur instantaneously (i.e. faster than light) in order to reproduce the behavior observed in quantum systems. Note that this does not necessarily mean that QM itself involves non-local or instantaneous communication, it just means that hidden variable accounts of QM would require these, or similar, drastic elements to be viable.

... or when it was just about particles with opposite properties.

I'm not sure what you mean by this.

"a model that employs identical particles that have hidden attributes/properties which locally determine the outcome of measurements." is what I mean. But as I understand the particles properties are mirrored (spin up for one is spin down for the other)

 

[ThomasT]

Maybe this will help clearing things up: can you please describe where exactly you think this author "[URL Wiki[/URL] goes wrong (and please use external references if possible that support your vision)?

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

I agree.

Physically, Bell's theorem proves that local hidden variable theories cannot remove the statistical nature of quantum mechanics.

I agree with this also.

Philosophically, Bell's theorem implies that if quantum mechanics is correct, the universe is not locally deterministic.

No, it only means that lhv models of entangled states, requiring separability, are incompatible with qm's representation of such states in a nonseparable form -- which is due to the statistical dependencies that the experiments are designed to produce. Statistical dependence doesn't imply nonlocality.

Neither the existence of nonlocality nor the nonexistence of a reality underlying the objective reality of instrumental behavior is implied by violations of Bell inequalities.

 

[RUTA]

No, it only means that lhv models of entangled states, requiring separability, are incompatible with qm's representation of such states in a nonseparable form -- which is due to the statistical dependencies that the experiments are designed to produce. Statistical dependence doesn't imply nonlocality.

Neither the existence of nonlocality nor the nonexistence of a reality underlying the objective reality of instrumental behavior is implied by violations of Bell inequalities.

So, are you saying it can be a nonseparable "reality underlying the objective reality of instrumental behavior" rather than nonlocality? That's what I showed you from Howard previously, but you said that wasn't your point. I don't see what else the above statement leaves. Nonseparability and nonlocality are generally understood to exhaust the options, so if you have yet another, you should publish it.

 

[ajw1]

No, it only means that lhv models of entangled states, requiring separability, are incompatible with qm's representation of such states in a nonseparable form -- which is due to the statistical dependencies that the experiments are designed to produce. Statistical dependence doesn't imply nonlocality.

Neither the existence of nonlocality nor the nonexistence of a reality underlying the objective reality of instrumental behavior is implied by violations of Bell inequalities.

Since you don't provide any external references we must conclude that you are expressing a personal view, not supported by peer reviewed articles. You should know that - without judging your view - this is prohibited by forum rules.

So again I challenge you to support your view by references.

 

[ThomasT]

So, are you saying it can be a nonseparable "reality underlying the objective reality of instrumental behavior" rather than nonlocality?

I'm saying that the only thing one can infer from violations of Bell inequalities is nonseparability of the joint state, which is sufficiently due to statistical dependence.

The statistical dependence results from modification of the sample space at one end associated with detection events at the other end. The pairing or matching up of the detection attributes accumulated in the separate data sets is done through strictly local transmissions and interactions.

 

[ThomasT]

Since you don't provide any external references we must conclude that you are expressing a personal view, not supported by peer reviewed articles. You should know that - without judging your view - this is prohibited by forum rules.

So again I challenge you to support your view by references.

We're talking about the physical meaning of quantum nonseparability. If that's prohibited in this forum, then I apologize.

Bell showed that the essential feature (separability) of any lhv formalism of quantum entanglement is incompatible with the essential feature (nonseparability) of the standard qm entanglement formalism.

This incompatibility, by itself, implies nothing about what does or doesn't exist in the reality that underlies instrumental behavior.

 

[ajw1]

We're talking about the physical meaning of quantum nonseparability. If that's prohibited in this forum, then I apologize.

Bell showed that the essential feature (separability) of any lhv formalism of quantum entanglement is incompatible with the essential feature (nonseparability) of the standard qm entanglement formalism.

This incompatibility, by itself, implies nothing about what does or doesn't exist in the reality that underlies instrumental behavior.

Bell's assumption is that given the experimental setup there is a limit to the correlation of the findings that can be explained by experimental setup/local factors. A higher correlation must be due to nonlocal behavior. This is the common view supported by most scientists.

Since you're view contradicts this common view you must supply hard evidence in the form of citations from peer reviewed articles, otherwise it’s just like crackpot science (and of course forum rules are made to prevent crackpot science being discussed).