Is Quantum Entanglement Just Correlation or a Real Physical Process?

[ThomasT]

We define nonlocality as a direct influence of one object on another, distant object, contrary to our expectation that an object is influenced directly only by its immediate surroundings.

Ok. But quantum nonlocality refers to logical rather than physical connections, and is just one of many misnomers that have become defacto standards in the literature.

Consider an EPR experiment, measuring spins. With parallel analyzers, we find that measurement of the spin on one side instantly predicts the result on the other.

This is just a result of the experimental designs necessary to produce entanglement. No instantaneous physical connection between A and B is implied. Quantum nonlocality is acausal.

If you do not believe one side can have a causal influence on the other, you require the results on both sides to be determined in advance (the Bertlmann's socks argument).

I'm not familiar with the socks argument, but entanglement experiments are designed to impart a common property to spatially separated entities, and then correlate joint detections with a global parameter. No ftl causal connection or transmission between A and B is necessary to at least begin to understand entanglement correlations. But, of course, events on either side will influence the global experimental situation.

But this has implications for non-parallel settings (e.g. measure spin on axes 45 degrees apart in the two wings) which conflict with quantum mechanics (Bell).

Any formulation which doesn't take into account the global nature of entanglement experimental designs will conflict with the quantum mechanical account, and the experimental results.

Bell's analysis showed that any account of quantum phenomena needs to be non-local, not just any 'hidden variables' account i.e. nonlocality is implied by the predictions of standard quantum theory itself.

No. Bell's analysis showed that a separable, or factorable (which was taken to be the most important feature of any lhv ansatz), formulation was incompatible with the qm account of entanglement.

Such a separable lhv account would only be possible if quantum behavior were trackable to an extent that's precluded by the principles forwarded in the CI.

The predictions and form of standard quantum theory don't imply physical nonlocality. They're a product of our ignorance of what's actually going on beneath the instrumental level. They imply that any attempt at an account of underlying causes will always be an exercise in speculative metaphysics.

Thus, if nature is governed by these predictions (which it is, according to real experiments) then nature is non-local.

Faulty reasoning.

This is essentially because the many-particle wave function in the Schroedinger equation is defined on the configuration space of the system, an abstraction which combines or binds distant particles into a single irreducible reality.

The correlations are the product of the (global) nature of entanglement experimental designs. It has nothing to do with ftl or instantaneous anything traveling between spacelike separated events.

So nonlocality - spooky action at a distance if you like - sounds strange and yet it is experimentally verifiable.

As I mentioned in a previous post, physical action-at-a-distance is meaningless. However, its logical counterpart is evident in any entanglement experiment. Events at either A or B (instantaneously ) affect the global experimental situation.

However, standard QM is not self-consistent due to the measurement problem. This is solvable only by granting real physical existence to theory objects.

This is the mistake that leads to unresolvable disputes about various weird entailments: assume that the deterministic components of the formalism are descriptions of underlying behavior and see where that takes you.

Standard QM is thus fundamentally an anti-realist stance - the wave function is just about probabilities, but probabilities of what?

Probabilities of instrumental behavior :uhh:? If limiting our statements on reality to the only level of reality that we can unambiguously communicate anything about is anti-realistic, then, yes, standard qm is anti-realistic -- and realism refers to metaphysical speculation.

Something does travel - of course - along different paths in, say, an interference experiment; to refuse to call it 'real' is merely to play with words.

Nobody is denying that what happens between emitters and detectors is real. But what can you say about it apart from the instrumental behavior? I agree that some inferences seem inescapable. But combining the more or less descriptive or realistic (read: speculative metaphysics) components of both classical and quantum physics falls far short of a comprehensive understanding of Nature.

Instrumentalist Copenhagen QM is effectively 'an idea for making it easier to evade the implications of quantum theory for the nature of reality' (Deutsch).

Deutsch is wrong in his evaluation of the CI, which is, in its entirety, the only comprehensive interpretation of quantum theory. The other so-called interpretations are actually just metaphysical adjuncts which, in order to actually do any real physics, must resort to the same (instrumental) probability calculus which characterizes standard qm.

Anyway, despite the CI, we're still free to speculate about the deep nature of reality based on quantum theory and experiments or any other source.

The positivist belief that empirical adequacy plus a formalized proof procedure is the best any theory can properly aspire to is - when you think about it - bizarre.

Maybe the standard fundamental theory(ies) will become more 'realistic'. Be patient. Physics is in its infancy.

Regarding ftl transmissions -- who knows, maybe they're real, however your thinking on, and reasons for believing in, spooky action at a distance are definitely flawed.

Finally, to your four points vis Maudlin:

* Violation of Bell's inequality does not require superluminal matter or energy transport

Correct.

* Violation of Bell's inequality does not entail the possibility of superluminal signalling

Correct.

* Violation of Bell's inequality does require superluminal causal connections.

Incorrect.

* Violation of Bell's inequality can be accomplished only if there is superluminal information transmission.

Incorrect.

Incompatibility between the salient features of the lhv formulation and the experimental design is sufficient to produce violation of the Bell inequality.

Violation of a Bell inequality is expected in experiments designed to produce statistically nonseparable data sets vis locally transmitted common cause(s).

Violation of Bell's inequality is used as an indicator of quantum entanglement. It isn't, afaik, considered an indicator of ftl or instantaneous physical propagations.

 

[ajw1]

No instantaneous physical connection between A and B is implied. Quantum nonlocality is acausal.

What is the proof for this? As I understand the EPR experiments suggests otherwise.

 

[RUTA]

What is the proof for this? As I understand the EPR experiments suggests otherwise.

There are causal explanations of EPR-Bell experiments. For example, the Bohmians use space-like causal connections (faster than light) and the backwards causation camp uses time-like connections whereby there is no preferred causal direction -- typically past causes future, but they say simply the two events are causally related. The latter is equivalent to blockworld, but not all backwards causation types appreciate that point

 

[ajw1]

Yes, several interesting causal and acausal (MWI) interpretations have been mentioned in this topic.

But if one claims QM nonlocality to be acausal, I would like to know what evidence there is for this claim.

 

[RUTA]

Yes, several interesting causal and acausal (MWI) interpretations have been mentioned in this topic.

But if one claims QM nonlocality to be acausal, I would like to know what evidence there is for this claim.

Exactly. My post #73 was meant to support your post #72 whereby you first issued this challenge. I should've quoted the point you were challenging, but I haven't figured out how to embed "multiple quotes" in my posts. Sorry for the confusion.

 

[WaveJumper]

What if entangled particles are traveling back in time(retrocausality) any time we make a measurement on one of their observables, thus eliminating the spatial separation between them?

 

[ThomasT]

What is the proof for this? As I understand the EPR experiments suggests otherwise.

There are causal explanations of EPR-Bell experiments. For example, the Bohmians use space-like causal connections (faster than light) and the backwards causation camp uses time-like connections whereby there is no preferred causal direction -- typically past causes future, but they say simply the two events are causally related. The latter is equivalent to blockworld, but not all backwards causation types appreciate that point.

Yes, I agree that quantum nonlocality is causal. I stand corrected.

I was thinking of quantum nonlocality as being synonymous with quantum entanglement in standard qm -- which it isn't. Quantum entanglement, wrt standard qm, is acausal.

Nonlocality is associated with certain 'realistic' metaphysical reformulations of, or supplements to, standard qm.

The current matters of fact are:

Nonlocality isn't part of, or implied by, standard qm.
Nonlocality hasn't been demonstrated experimentally.

So, as far as matters of fact are concerned, we can say that "spooky action at a distance" doesn't exist except as a speculative metaphysical explanation for quantum entanglement correlations.

Everything except a certain view of the meaning of Bell's theorem suggests that quantum entanglement correlations are due to common causal factors involving local transmissions/interactions.

Complications arise if Bell's theorem is taken to rule out such a common cause (local) scenario.

The salient feature of Bell's lhv formulation doesn't correspond to common cause or locality, but rather to the independence of the spatially separated statistical accumulations. However, due to the experimental designs necessary to produce entanglement correlations, the separate statistical accumulations aren't independent. So, experimental violations of inequalities based on Bell's ansatz don't rule out locality, but rather the statistical independence of the separate data sets (and such violations are therefore indirect indicators that experiments designed to produce quantum entanglement did in fact produce quantum entanglement).

The experimental production of quantum entanglement involves imparting related properties to separated disturbances whose joint detection attributes are correlated to some global measurement parameter -- and the correlations are what would be expected if everything in these experiments is proceeding within the constraint of local causality. For example, two identical optical emissions filtered and transmitted by two identical polarizers with parallel settings produce, in the ideal, identical detection attributes, (1,1) or (0,0), wrt each joint measurement, and perpendicular settings produce opposite detection attributes, (1,0) or (0,1), wrt each joint measurement. If the joint settings aren't parallel or perpendicular, then the detection attributes for each joint measurement are unpredictable, with the coincidence count approaching the qm prediction as the number of joint measurements increases.

 

[ajw1]

Nonlocality hasn't been demonstrated experimentally.

So, as far as matters of fact are concerned, we can say that "spooky action at a distance" doesn't exist except as a speculative metaphysical explanation for quantum entanglement correlations.

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

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.

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.

 

[zenith8]

Ok. But quantum nonlocality refers to logical rather than physical connections, and is just one of many misnomers that have become defacto standards in the literature.

This is just a result of the experimental designs necessary to produce entanglement. No instantaneous physical connection between A and B is implied. Quantum nonlocality is acausal.

etc..

ThomasT,

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

A standard reference such as the Stanford Encyclopedia of Philosophy article on "http://plato.stanford.edu/entries/qm-action-distance"" dismisses your argument in three of its several thousand lines:

"Orthodox QM is a good instrument for predictions rather than a fundamental theory of the physical nature of the universe. On this instrumental interpretation, the predictions of QM are not an adequate basis for any conclusion about non-locality: the theory is just an incredible oracle (or a crystal ball), which provides a very successful algorithm for predicting measurement outcomes and their probabilities. It offers little information about ontological matters, such as the nature of objects, properties and causation in the quantum realm."

So 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.

Having just read the above article it pretty much agrees with my post but does a much better job of it as you might expect from an Encyclopedia article (though I note it doesn't appear to use many-worlds as a get-out clause, as I do, just many-minds, and adds a minor interest get-out clause about the definition of causation, which it then proceeds to dismiss).

See also Maudlin's excellent "https://www.amazon.com/dp/0631232214/?tag=pfamazon01-20" book which comes to the same conclusions:

"Violation of Bell's inequality shows that the *world* is non-local. It can be no criticism of a theory [like de Broglie-Bohm] that it displays this feature of the world in an obvious way."

or Redhead:

"Some sort of action at a distance - seems to be built into a reasonable attempt to understand the quantum view of reality."

and clearly I could supply several thousand more quotes from clever people along the same lines..

Just for fun, here's a typical review of Maudlin's book:

"There are many books which discuss the issue of quantum non-locality and discuss its connections to relativity theory. The vast majority of them, however, are either un-serious popular pap, or serious tomes written by professional philosophers who are at least as confused as the authors of the pap.

Maudlin's book stands out like a beacon of light in this fog of confusion and muddle-headedness. It is accessible to anyone with a basic high-school education in math and physics, yet surpasses the vast majority of technical papers on this subject in depth, clarity, and (most importantly) correctness. If you want to understand the issue of non-locality that makes some people worry so much about quantum theory and its consistency with relativity, read this book -- study this book -- and this holds whether you are a Joe Schmoe off the street or a famous Professor from (say) Boston University."

I couldn't agree more - read it!

So, my point is that the orthodox interpretation of QM is a prescription for avoiding fundamental questions - that is so because Bohr and Heisenberg designed it that way. It effectively debars all attempts to interpret the quantum formalism aside from their purely instrumental yield. You cannot use it to make the argument you are making.

For some reason you think this interpretation has some special status for discussing questions of this nature. It has no such status - other than purposefully restricting itself to stating the obvious. It wasn't even the first interpretation of QM - the de Broglie-Bohm one (which I strongly suspect will win out when all the old brainwashed guys die) beat it by at least two years. And in the ultra-modern era where we have to accept that quantum particles and matter waves actually exist - effectively because we can trap, see and manipulate them - Copenhagen is no longer sufficient.

So to summarize the difference:

I said (post #36):

(A) If there exists an objective reality, then Bell's/GHZ etc. theorems and subsequent experiments show that 'spooky action at a distance' is a genuine physical effect (in the absence of backwards time travel or many universes).

[I note by the way in your reponse to my post you fail to mention my three get-out clauses, thus implying my statement (A) consists of the words only between 'Bell' and 'effect'.]

ThomasT statement (I paraphrase):

(B): Because quantum physics is not about real objects, it is about the results of observations, then statement (A) is incorrect. Hence in quantum mechanics, nonlocality is acausal.

However, while the mathematical objects in quantum physics may not map onto real objects (despite the utter obviousness of de Broglie-Bohm) that does not matter. The unfortunate fact is that Bell's theorem is ultimately directly dependent neither on quantum physics, nor on the precise nature of the metaphysics. What one can say is that if there is an objective reality, that is if something which actually exists travels through the apparatus in an interference experiment, then the physical existence of nonlocality may be upheld (in the absence of backwards time travel or ..aaargghhh.. bazillions of new universes being created every time something happens). Note that this is true whatever the nature of the real thing in question. It may be a Bohmian particle and wave field, it may be just a wave function, it may be an invisible cow with bells on - it doesn't matter for the sake of this argument. It merely needs to objectively exist.

Now, I know you don't actually deny the existence of an objective reality, because you say so explicitly. I quote:

"Nobody is denying that what happens between emitters and detectors is real. But what can you say about it apart from the instrumental behavior?"

Well, given that 'whatever it is' that goes through the holes in a double-slit experiment produces a perfectly standard interference pattern then you can say a wave of some kind must go through the slits. If it wasn't a wave, then no interference pattern would be produced. (If the wave function represents 'knowledge' then how do you get interference, exactly?)

And given that the wave pattern is only built up over millions of individual particle detection events, then it's highly likely that particles go through the slits as well, and that they are 'guided' by the waves (via a 'quantum force').

Hmm.. do you recognize the theory? Wave-particle duality implying waves and particles? No, it can't be true. Feynman said so:

"How does it really work? What machinery is actually producing this thing? Nobody knows any machinery. Nobody can give you a deeper explanation of this phenomenon than I have given; that is, a description of it."

I don't claim that the above inferences are unique, but it certainly is very interesting that using them, one can write down a more or less obvious 'causal explanation' for just about every phenomenon of quantum physics. Ever tried explaining, say, Pauli's exclusion principle to an undergraduate using only the Orthodox interpretation (er.. "the indistinguishability of electrons leads to er.. 'statistical repulsion' through er.. the Pauli force and thus same-spin electrons - which don't er.. exist until you look at them - tend to avoid each other". Anyone?). It's just not possible with a theory that denies the possibility of explanatory clarity on a point of principle. Add the 'quantum force' - which is identical to the so-called Pauli force and whose mathematical form is sitting, usually unnoticed, already in the QM formalism - and the explanation is easy.

Anyway, sadly, it doesn't matter what you can say about it. If the objects in an EPR experiment are real, then given our current knowledge about physics, nonlocality exists. The main difference of opinion seems to be that you think that 'realistic' means 'engaging in speculative metaphysics' rather than 'objectively existing', and that 'metaphysics' appears to be some sort of term of abuse. Realist theories of QM are no more 'metaphysical' than any other theory in physics about things that you can't see directly (curved space, quarks, black holes etc.) And at least the realistic theories themselves explain why you can't directly measure e.g. electron trajectories.

We cannot accept, as a legitimate argument form, inferences from the unobservability of a distinction to the unreality of the distinction. And I suspect you know that.

 

[ueit]

If the objects in an EPR experiment are real, then given our current knowledge about physics, nonlocality exists.

I do not think that one can reach the above conclusion. Imagine the folowing example:

A computer program places points of different colors on the screen. You observe that red points appear always in pairs at opposite places of the screen. Two explanations are possible:

1. The program is designed to place directly those points, at the same time, at distant positions (this would be non-local theory)

2. There is a fractal that computes the color of each point from the color of nearby points. The correlations appear as a result of the fractal formula, a kind of emergent symmetry. (this is a local theory)

As far as I know, both can be true for our universe and there is no way to experimentally distinguish between them unless they follow from a theory that makes other, verifiable predictions as well.

 

[RUTA]

If there exists an objective reality, then Bell's/GHZ etc. theorems and subsequent experiments show that 'spooky action at a distance' is a genuine physical effect (in the absence of backwards time travel or many universes).

What one can say is that if there is an objective reality, that is if something which actually exists travels through the apparatus in an interference experiment, then the physical existence of nonlocality may be upheld (in the absence of backwards time travel or ..aaargghhh.. bazillions of new universes being created every time something happens). Note that this is true whatever the nature of the real thing in question. It may be a Bohmian particle and wave field, it may be just a wave function, it may be an invisible cow with bells on - it doesn't matter for the sake of this argument. It merely needs to objectively exist.

Is there a proof of this published somewhere? Prima facie it strikes me as true, but I tend to think like a physicist so I don't trust my intuition in philosophical matters

 

[DrChinese]

Is there a proof of this published somewhere? Prima facie it strikes me as true, but I tend to think like a physicist so I don't trust my intuition in philosophical matters

I think zenith8 is simply giving a restatement of Bell's Theorem. I.e. if reality holds, then locality does not.

 

[RUTA]

I think zenith8 is simply giving a restatement of Bell's Theorem. I.e. if reality holds, then locality does not.

I guess my question then relates to "reality." Zenith8 explicitly says if there is something(s) moving through the apparatus (wave, particle, cow, ...), then you must have non-locality (given EPR-Bell results). Just to make it clear, there are interpretations whereby NO THING moves through the apparatus to cause detector clicks, i.e., so-called "screened-off" entities don't exist. In those cases, you can have locality but sacrifice separability. So, I'm just wondering if it is necessarily true that you don't have such an option with the existence of screened-off causal agents.

 

[WaveJumper]

I think it's a bit arrogant that in 6 pages no one has questioned the ability of the human mind to comprehend everything. It's an assumtion that has brought us to the technological development seen today and without it science will more or less collapse.

But deep down inside, do all of you guys always entertain the idea that we have the imagination/intellect to understand and explain how absolutely everything works?

What if we lack the imagination to picture a yet unknown mechanism by which quantum entanglement works in a local objectively existent universe? What if the reality/universe isn't completely comprehensible?

 

[zenith8]

I guess my question then relates to "reality." Zenith8 explicitly says if there is something(s) moving through the apparatus (wave, particle, cow, ...), then you must have non-locality (given EPR-Bell results). Just to make it clear, there are interpretations whereby NO THING moves through the apparatus to cause detector clicks, i.e., so-called "screened-off" entities don't exist. In those cases, you can have locality but sacrifice separability. So, I'm just wondering if it is necessarily true that you don't have such an option with the existence of screened-off causal agents.

Oh, for God's sake, lads.. it's not the 1920s any more.

Modern progress in experimental physics shows without doubt that quantum entities are in fact real. They exist whether we 'observe' them, conduct experiments with them, or not.

Single atoms and even electrons can be isolated and trapped in containment vessels for long periods. You can repeat the examination over and over again and get the same data. Individual atoms can be 'pushed around', arranged into patterns (which can also be imaged - IBM anyone?) and otherwise manipulated. These experiments all yield consistent results and information about quantum entities using a variety of techniques and under different conditions.

"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.

See the attached images. Yes - those are atoms.

Thus, in my opinion, the de Broglie-Bohm ontology of having particles and waves present in a quantum system seems by far the most sensible way to look at these things.

In 1927 it may have been considered reasonable for Bohr et al. to design an interpretation of QM as an algorithm for obtaining statistical predictions for the results of experiments (and thus as a prescription for avoiding fundamental questions). It was reasonable because in 1927 quantum entities were not observable in experiments and thus could be considered - though this is a non sequitur - not real. In the 21st century, considering that something real doesn't move through the slit if you diffract atoms is just laughable.

``... the idea of an objective real world whose smallest parts exist objectively in the same sense as stones or trees exist, independently of whether or not we observe them ... is impossible.'' [Heisenberg, 1958]

Many older physicists get really angry if one dares to suggest that Heisenberg was merely deluded. Clearly most of them will never overcome the dominant though patterns of the prevailing paradigm of orthodox QM (such as the denial of an independently existing quantum realm) and, sadly, it will almost certainly require a generational change for this to be otherwise.

 

[zenith8]

I think it's a bit arrogant that in 6 pages no one has questioned the ability of the human mind to comprehend everything. It's an assumtion that has brought us to the technological development seen today and without it science will more or less collapse.

But deep down inside, do all of you guys always entertain the idea that we have the imagination/intellect to understand and explain how absolutely everything works?

What if we lack the imagination to picture a yet unknown mechanism by which quantum entanglement works in a local objectively existent universe? What if the reality/universe isn't completely comprehensible?

You're completely correct, of course. I guess we should all just give up then.

Anyone for a beer down the pub this evening? We can discuss the future direction of our ruined careers..

 

[WaveJumper]

You're completely correct, of course. I guess we should all just give up then.

Anyone for a beer down the pub this evening? We can discuss the future direction of our ruined careers..

I did not imply that the research should somehow stop, but conjecturing that the universe is non-local or objectively existent or there are many worlds or that observation creates reality or that we are all one wholeness, etc. is no more evidenced than the idea that the universe may not be fully 100.00% comprehensible.

Was the universe fully tailored for the human mind to comprehend and explain?

It's common knowledge that not everyone in the physics community believes in a theory of everything. There is a chance different than zero that it might be a red herring(though i don't subscribe to the idea, i don't hold absolute confidence that such a theory exists)

 

[DrChinese]

In the 21st century, considering that something real doesn't move through the slit if you diffract atoms is just laughable.

``... the idea of an objective real world whose smallest parts exist objectively in the same sense as stones or trees exist, independently of whether or not we observe them ... is impossible.'' [Heisenberg, 1958]

Now you are falling prey to the EPR argument, which is simply wrong. You cannot assume objective reality of observables, which they did tautologically. There may be an objective reality, true, but this cannot be assumed. Non-realistic solutions are viable at this time.

 

[zenith8]

Now you are falling prey to the EPR argument, which is simply wrong. You cannot assume objective reality of observables, which they did tautologically. There may be an objective reality, true, but this cannot be assumed. Non-realistic solutions are viable at this time.

I'm not assuming it. I'm looking at it..

I'm not sure I understand your point. Can you elaborate?

 

[DrChinese]

I'm not assuming it. I'm looking at it..

I'm not sure I understand your point. Can you elaborate?

Sure. EPR concluded correctly that either: a) QM was incomplete (as they defined incompleteness); or b) "... the reality of P and Q depend upon the process of measurement carried out on the first system, which does not disturb the second system in any way."

b) is a direct quote from the 1935 paper, and is considered to be observer-dependent realism. I.e. not objective realism at all - which is defined to be observer independent - and thus non-realistic. Of course they did not even consider the idea of "spooky action at a distance" as a possibility.

Their tautology is evident is the sentence following: "No reasonable definition of reality could be expected to permit this." So they throw out b) and therefore conclude a). However, there is actually no rational or logical reason to exclude b). This was driven home nearly 50 years later with Aspect's experimental test of Bell's Theorem. It was shown that the EPR premise (a=true and b=false) was incorrect because actually a=false and b=true.

The point is that if you toss out non-realistic solutions, as EPR did (they also threw out non-local solutions so don't feel bad), you run smack into logic problems. Better to make it an opinion or a hunch, rather than an absolute.

 

[WaveJumper]

I'm not assuming it. I'm looking at it..

I'm not sure I understand your point. Can you elaborate?

May i elaborate instead of DrChinese?

That you have seen an image of atoms does not mean that they are there when you aren't probing/measuring them with a scanning tunneling microscope. In fact, the multiple double slit experiments all show the opposite(including the one done with atoms).

 

[zenith8]

May i elaborate instead of DrChinese?

That you have seen an image of atoms does not mean that they are there when you aren't probing/measuring them with a scanning tunneling microscope. In fact, the multiple double slit experiments all show the opposite (including the one done with atoms).

Read my post again. It's not just about seeing a photo of atoms once. I said:

"Single atoms and even electrons can be isolated and trapped in containment vessels for long periods. You can repeat the examination over and over again and get the same data. Individual atoms can be 'pushed around', arranged into patterns (which can also be imaged) and otherwise manipulated. These experiments all yield consistent results and information about quantum entities using a variety of techniques and under different conditions."

So the point is that you can now explore the same individual quantum system over and over again and get the same data each time. Not only can we trap a quantum particle, we find that it is still in its trap after intervals of time where there have been no interactions. Single atoms can be imaged and re-imaged with the same results. This is only possible because quantum systems and elementary particles exist whether we observe them, conduct experiments with them, or not.

Note also the stuff about matter wave optics.

How exactly do multiple double slit experiments show the opposite?

 

[WaveJumper]

Read my post again. It's not just about seeing a photo of atoms once. I said:

"Single atoms and even electrons can be isolated and trapped in containment vessels for long periods. You can repeat the examination over and over again and get the same data. Individual atoms can be 'pushed around', arranged into patterns (which can also be imaged) and otherwise manipulated. These experiments all yield consistent results and information about quantum entities using a variety of techniques and under different conditions."

So the point is that you can now explore the same individual quantum system over and over again and get the same data each time. Not only can we trap a quantum particle, we find that it is still in its trap after intervals of time where there have been no interactions. Single atoms can be imaged and re-imaged with the same results. This is only possible because quantum systems and elementary particles exist whether we observe them, conduct experiments with them, or not.

Note also the stuff about matter wave optics.

How exactly do multiple double slit experiments show the opposite?

While it's obviously true that particles can be confined/trapped, all those quantum objects can't be localised(objectified) until they are measured, due to the wave nature of matter. No one knows where they are until they are measured, all we can say about them is a probability that they might be somewhere.

Why they appear the way they do and maintain the order we see in our macro world is the problem of outcomes which is unsolvable at this time.

 

[zenith8]

While it's obviously true that particles can be confined/trapped, all those quantum objects can't be localised(objectified) until they are measured, due to the wave nature of matter. No one knows where they are until they are measured, all we can say about them is a probability that they might be somewhere.

Why they appear the way they do and maintain the order we see in our macro world is the problem of outcomes which is unsolvable at this time.

Not so. That's just what you've been led to believe.

Atoms stay where they are put. The IBM guys could repeatedly re-image the xenon atoms spelling IBM on the nickel surface, and see that they remained undisturbed between observations. The idea that the atoms take a quick trip around the universe when you're not looking at them and then fly back into precisely the same configuration when you do is no more believable than saying the world ceases to exist when you close your eyes. Read what the experimentalist guys themselves say about this - especially the more modern stuff that has been done in the last few years..

 

[DrChinese]

While it's obviously true that particles can be confined/trapped, all those quantum objects can't be localised(objectified) until they are measured, due to the wave nature of matter. No one knows where they are until they are measured, all we can say about them is a probability that they might be somewhere.

I don't think the question is so much whether the particles exist or not, when not observed. The question is whether they have all possible observable-attributes at times when no observation is occurring. And further, whether those observable-attributes have specific well-defined values at all times.

The answer to that question appears to be NO per many recent experiments (not just Bell, also GHZ, Hardy, etc.). So you would want to accept non-realism and reject non-locality to be consistent with experiment. On the other hand, non-realism is a weird concept and non-locality is easier to imagine as a mechanism. Thus explaining its popularity.

 

[WaveJumper]

Not so. That's just what you've been led to believe.

Atoms stay where they are put. The IBM guys could repeatedly re-image the xenon atoms spelling IBM on the nickel surface, and see that they remained undisturbed between observations. The idea that the atoms take a quick trip around the universe when you're not looking at them and then fly back into precisely the same configuration when you do is no more believable than saying the world ceases to exist when you close your eyes. Read what the experimentalist guys themselves say about this - especially the more modern stuff that has been done in the last few years..

Did someone observe the wave properties of matter?

I did not say that IBM could not repeatedly re-image the same atoms. I specifically said that this fact, that atoms appear in classical matter the way they do, is the problem of outcomes(objectification). The problem of outcomes seeks the answer to the question - why is a particular eigenstate selected out of all other(to maintain our classical predictability and order, aka deterministic world).

 

[zenith8]

Did someone observe the wave properties of matter?

Read my post again - I devoted several paragraphs and one picture to it. There is a whole field of physics called matter wave optics which does precisely that.

I did not say that IBM could not repeatedly re-image the same atoms. I specifically said that this fact, that atoms appear in classical matter the way they do, is the problem of outcomes(objectification). The problem of outcomes seeks the answer to the question - why is a particular observable selected out of all other(to maintain our classical predictability and order)

Look, they're just atoms, with a position. You've been conditioned to believe that something weird is going on in such a situation. There (almost certainly) isn't.

Let's say it like this: the methods of physics have yielded compelling evidence for accepting the existence of the quantum realm. We might take a leaf out of the pages of the history of science and say that it now remains a matter of how much evidence is required to convince the sceptics. Whether it be the acceptance of a heliostatic over an Earth-centred solar system or the Einsteinian over the Newtonian worldview, it was the weight of the evidence which finally decided the question.

So answer me this: what evidence would be needed to convince you of the reality of atoms?

 

[WaveJumper]

Read my post again - I devoted several paragraphs and one picture to it. There is a whole field of physics called matter wave optics which does precisely that.
Look, they're just atoms, with a position. You've been conditioned to believe that something weird is going on in such a situation. There (almost certainly) isn't.

Let's say it like this: the methods of physics have yielded compelling evidennce for accepting the existence of the quantum realm. We might take a leaf out of the pages of the history of science and say that it now remains a matter of how much evidence is required to convince the sceptics. Whether it be the acceptance of a heliostatic over an Earth-centred solar system or the Einsteinian over the Newtonian worldview, it was the weight of the evidence which finally decided the question.

So answer me this: what evidence would be needed to convince you of the reality of atoms?

I never said or implied that they aren't real, i was merely opposed to the way you were trying to prove that atoms were real(by showing an image of atoms). My whole statement during the debate has been:

It's meaningless to talk about observables before we measure them. (i.e. from this we cannot infer if there is or is not an objective reality, an image of atoms is not enough)

 

[zenith8]

I never said or implied that they aren't real, i was merely opposed to the way you were trying to prove that atoms were real(by showing an image of atoms). My whole statement during the debate has been:

The image of atoms was not the main point - it was just meant to be a helpful visual addition to the text. I apologize if you took it otherwise.

It's meaningless to talk about observables before we measure them. (i.e. from this we cannot infer if there is or is not an objective reality, an image of atoms is not enough)

In general, no. In the Copenhagen interpretation, yes - but this is a circular argument, since Copenhagen defines itself to be only concerned with the results of measurements.

 

[WaveJumper]

In general, no. In the Copenhagen interpretation, yes - but this is a circular argument, since Copenhagen defines itself to be only concerned with the results of measurements.

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

 

[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