Is Quantum Entanglement Just Correlation or a Real Physical Process?

[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).