Questions on Entanglement and Double-Slit Experiment

[RandallB]

First off, in the context you used "it" for was not for the person Bell

I don't use "it" for persons, so the answer is "A fully deterministic theory”.

you were referring to the "Bell Theorem" or its application.

And just declaring the "assumption that we live in a local deterministic universe" does show anything beyond establishing a point of faith maybe.
And GR has not be shown to be "local" - plenty to read by Smolin on the requirement for indeterminate background for GR (Non-local IMO) that has not been disproved to any reasonable satisfaction .

And the idea that when setting of two space like separated wheels (detector switches) we a powerless to use free will or judgment to set them differently that what the Big Bang preset deterministic universe has already decided what we will do, is just pointless. Talk about an un-testable theory - it demands that we can only know a proof for it IF it has been predetermined for us to learn it.
If you understand what LOCAL means, you would recognize this as a Non-Local Local theory. It is only local within itself as it reaches out to its preset deterministic values to explain correlations. Just like non-local BM and MWI are local within those theories, using invisible guide-waves and multi-dimensional extended realities to explain correlations within their theory.

A deterministic universe (classical or non) is not a Local (Bell Local) theory, and if you want to apply Occum's to the Non-locals this one IMO falls to the bottom of that list.

Personally I think realty is local and real does not need some kind of strange extended reality; but that is just an opinion, I don't go around declaring it as a fact. But unlike yours I know exactly the tool that is required to turn my opinion to fact, and that is the Bell Theorem itself. And it only need do so once, and all the non-locals will fall including yours. But no individual Non-local theory even has a tool that has an expectation of excluding other theories.
So if you cannot even produce a tool that might provide a proof of your theory at least state it as an opinion or personal preference and do not demand it be accepted as a simple fact.

 

[exeric]

Hi, I've done some study on this problem of non-locality and have reached my own conclusions. I've written a paper with my own plausible explanation for it. But rather than muck things up with my own ideas right off the bat I'd like to pose some questions for people who are not afraid to think outside of the box.

1.The Bell theorem, as I understand it, simply "assumes" that the EPR paper proposed a condition that required local variables. It may be more logically said that John Bell simply couldn't think of any other way of looking at quantum entanglement than in this way. My understanding is that Einstein never explicitly called for local variables but just for local "realism". In 1930 or thereabouts he produced his own theory of "teleparallelism". This theory could be said to have anticipated the results of quantum entanglement but through a different mechanism - namely "torsion".

2. If Einstein himself proposed a theory 5 years earlier in which non-locality of cause and effect could possibly happen then it could be said that what Einstein was more properly saying in the EPR paper is that quantum entanglement can exist, but that we just need to fill in our picture of physics in a way that it makes sense. It's interesting to me that so many physicists seem to ignore the title of the EPR paper: "Can The Quantum Mechanical Description of Physical Reality Be Considered Complete?"

It almost seems that the physics community has just built this straw man of "local variables" that Bell produced to show Einstein didn't know what he was talking about. Clearly he did and the title of the paper neatly summed it up what he was "really" saying.

Eric

 

[lalbatros]

Dear all,

I have asked this several times here and there. Sorry to repeat myself, for those concerned.

My question: how much can we say that entanglement is an absolute concept?

I explain more:

Let's go back to our particle A and particle B.
Particles are "just" states of a quantum field, the electromagnetic field for example when photons are involved.

This leads me to the idea that entanglement depends on the point of view, since it depends on the states that one takes as reference. In other words, a state can be a mixed state in a basis B and it could be a pure state in another basis B'.

Nevertheles, I have the intuitive feeling that entanglement should be something measurable and with a kind of absolute meaning, like the entropy in statistical physics.

What do you know about that, what are your ideas?
Some references welcome.

Thanks,

Michel

 

[ZapperZ]

Dear all,

I have asked this several times here and there. Sorry to repeat myself, for those concerned.

My question: how much can we say that entanglement is an absolute concept?

I explain more:

Let's go back to our particle A and particle B.
Particles are "just" states of a quantum field, the electromagnetic field for example when photons are involved.

This leads me to the idea that entanglement depends on the point of view, since it depends on the states that one takes as reference. In other words, a state can be a mixed state in a basis B and it could be a pure state in another basis B'.

Nevertheles, I have the intuitive feeling that entanglement should be something measurable and with a kind of absolute meaning, like the entropy in statistical physics.

What do you know about that, what are your ideas?
Some references welcome.

Thanks,

Michel

Even with your explanation, I'm not sure what you mean by an "abolute concept".

Take note that the EPR-type experiments are just ONE consequence of the property of entanglement (and Einstein's non-locality). The fact that "entanglement" means, mathematically, that the state function of the entangled property is not separable, indicates that it can have other measurable consequences.

One such consequence is that the entangled objects' property can be thought of to be one "macro" particle. If that is the case, then 2 entangled photons behave as if it is just one "macro" photon with twice the energy, and thus, half the wavelength. What this means is that if you do optical measurement with such photons, you CAN beat the diffraction limit of the original light source!

This has been done[1]! The higher order interference pattern has been seen, and this is completely consistent with the QM prediction. So I don't know if you consider this as an "absolute concept", but it certainly is very real if you base it on emprical evidence so far.

Zz.

[1] P. Walther et al. Nature v.429, p.158 (2004).

 

[lalbatros]

ZapperZ,

The way you formulate it is clearer indeed:

The fact that "entanglement" means, mathematically, that the state function of the entangled property is not separable, indicates that it can have other measurable consequences.

Indeed, what I mean is that the separability depends on the choice of the basis.
This choice actually depends on the experiment to be analysed in tems of entanglement.

Am I right to say that:

a pair of spins analysed as up or down may be in a separable state
while the same state analysed as a pair of spins left or right would not be separable​

However, I belong to the set of people who believe that the measurement postulate is not more than a pedagogical convenience (or maybe a king of closure of the theory). But still it represents -in some way- an interaction process. I skip here more discussions about the entangled state system + observer after the measurement. However this indicates that entanglement will play a role not only in a (possibly EPR) measurement process, but in any interaction.

Therefore, I believe entanglement is a very important thing. Not only because of some EPR paradox, but even more because I think it plays a big role in the quantum evolution. Maybe this is trivial, but I don't know how to highlight that from -say- the Schrödinger equation.

Considering all that, it could make sense that indeed entanglement is a "relative" property of a composite system. It is relative to the basis states considered (like a reference frame!), and in the end these basis states are related to an (EPR) measurement to be performed.

I was asking myself if entanglement could be given an absolute meaning, and therefore an absolute measure of entanglement could be defined. If there was a "preferred basis", then it would be the case.

Any ideas, suggestions, readings ... ?

Michel

 

[MaverickMenzies]

Hi lalbatros,

There has been some work done to attempt to describe the entanglement of quantum states without requiring a recourse to the tensor product decomposition i.e. the decomposition into subsystems. Here are a couple of e-prints that I have found:

quant-ph/0308043, quant-ph/0305023.

I also think that Prof. Vlatko Vedral (at the university of leeds) has some ideas to relate multipartite entanglement in solid state systems to some order parameter of the system.

I hope that this is of some use.

 

[Doc Al]

Am I right to say that:

a pair of spins analysed as up or down may be in a separable state
while the same state analysed as a pair of spins left or right would not be separable​

No. Whether a two-particle state is entangled or not does not depend on the choice of basis states used to describe it. Perhaps you are thinking of the fact that a "spin-up" state can be expressed as a superposition of "spin-left" and "spin-right" states?

 

[ttn]

No. Whether a two-particle state is entangled or not does not depend on the choice of basis states used to describe it. Perhaps you are thinking of the fact that a "spin-up" state can be expressed as a superposition of "spin-left" and "spin-right" states?

...although the number of terms in the quantum state function (which one might loosely think of as a measure of the "amount" of entanglement) can differ from basis to basis. This, by the way, is the source of the so-called "preferred basis problem" which advocates of the Many Worlds Interpretation are forced to worry about since they are sometimes in the business of "counting worlds" to try to derive Born's rule.

Also, repeating what a previous poster said, there are tons of papers on the question of trying to quantify the "amount" of entanglement. (For the reason I just pointed out, the number of terms in the quantum state function is not a good measure of this since it's basis-dependent!) Search, e.g., on arxiv for "entanglement measure" and lots of things will come up.

Finally, I might be wrong about this, but I got a vague sense that lalbatros was raising these questions about entanglement because of a confusion over Bell's argument for non-locality. Just for the record, the argument is *not* of the form: there's a kind of non-locality associated with entanglement, which is a pretty important/ineliminable feature of quantum theory, hence non-locality is a real physical thing. That's not the argument at all. My sense was that lalbatros was worried that maybe people accepted non-locality too easily (based on some argument like this), when, in fact, there is every reason to wonder if "entanglement" is even an absolute ineliminable concept. It is, after all, a feature of a *theory* -- a theory that there is tons of controversy about whether or to what extent it should be taken as providing a literal true description of physical reality.

I'm not sure I'm saying this very clearly. The point is, anyone who believes that nonlocality is a real feature of the physical world *based on the mere fact that orthodox quantum theory says that spatially separated systems can sometimes be in entangled states* is a crazy fool. Bell was no crazy fool. So anyone interested in understanding why Bell (and those who understand and hence follow him) believed nonlocality was a real physical phenomena, should go read Bell's papers where he explains this all very very clearly!

And now, just in case Zapper Z is still reading... I'm still anxiously waiting to hear what part of the argument in Einstein's Boxes you found unconvincing and/or why you thought the criticisms by Shimony and [that other guy whose name I can't remember] made sense...

 

[exeric]

Hi, I've done some study on this problem of non-locality and have reached my own conclusions. I've written a paper with my own plausible explanation for it. But rather than muck things up with my own ideas right off the bat I'd like to pose some questions for people who are not afraid to think outside of the box.

1.The Bell theorem, as I understand it, simply "assumes" that the EPR paper proposed a condition that required local variables. It may be more logically said that John Bell simply couldn't think of any other way of looking at quantum entanglement than in this way. My understanding is that Einstein never explicitly called for local variables but just for local "realism". In 1930 or thereabouts he produced his own theory of "teleparallelism". This theory could be said to have anticipated the results of quantum entanglement but through a different mechanism - namely "torsion".

2. If Einstein himself proposed a theory 5 years earlier in which non-locality of cause and effect could possibly happen then it could be said that what Einstein was more properly saying in the EPR paper is that quantum entanglement can exist, but that we just need to fill in our picture of physics in a way that it makes sense. It's interesting to me that so many physicists seem to ignore the title of the EPR paper: "Can The Quantum Mechanical Description of Physical Reality Be Considered Complete?"

It almost seems that the physics community has just built this straw man of "local variables" that Bell produced to show Einstein didn't know what he was talking about. Clearly he did and the title of the paper neatly summed it up what he was "really" saying.

Eric

I'd still be interested in any responses to what I said above. I realize what I'm saying maybe a little off in right field to some of you but I really think Bell's inequality is just a starting point for understanding quantum entanglement. It just shows that the non-locality of correlative effects exist but in no way addresses Einstein's real question. I think it misses the forest for the trees. Conversely, I think the EPR paper was concentrating on the forest - something which is done rarely in physics, even today. I promise I won't talk about my own ideas about QE if I can just get you guys to engage on this point.

Eric

 

[ZapperZ]

Indeed, what I mean is that the separability depends on the choice of the basis.
This choice actually depends on the experiment to be analysed in tems of entanglement.

Am I right to say that:

a pair of spins analysed as up or down may be in a separable state
while the same state analysed as a pair of spins left or right would not be separable​

I don't understand this part. How do you separate out, for example

$|\Psi> = |up>_1|down>_2 + |down>_1|up>_2$ ?

There are no unitary transformation to a different basis that you can do that separate them out, are there?

Zz.

 

[exeric]

ZapperZ,



However, I belong to the set of people who believe that the measurement postulate is not more than a pedagogical convenience (or maybe a king of closure of the theory). But still it represents -in some way- an interaction process. I skip here more discussions about the entangled state system + observer after the measurement. However this indicates that entanglement will play a role not only in a (possibly EPR) measurement process, but in any interaction.

Therefore, I believe entanglement is a very important thing. Not only because of some EPR paradox, but even more because I think it plays a big role in the quantum evolution. Maybe this is trivial, but I don't know how to highlight that from -say- the Schrödinger equation.

Considering all that, it could make sense that indeed entanglement is a "relative" property of a composite system. It is relative to the basis states considered (like a reference frame!), and in the end these basis states are related to an (EPR) measurement to be performed.

I was asking myself if entanglement could be given an absolute meaning, and therefore an absolute measure of entanglement could be defined. If there was a "preferred basis", then it would be the case.

Any ideas, suggestions, readings ... ?

Michel

I, myself don't think that quantum entanglement can be considered as something relative to the way that it is measured. It might have been an open question before the vast experimental evidence has built up, but I don't think it can be said anymore. Entanglement is not an "interpretative" event in that respect. And measurement only nails the quantum state of each of entangled composite particles at the instant it is measured.

I think you brought up a very interesting point about composite particles. This is the heart of the phenomena. It has only very recently been broadly realized that entanglement is not a rare event but probably plays a part in all particles that are made from composite particles. In this sense the assymptotic freedom of quarks in a proton could be considered just another aspect of quantum entanglement. In this special case it might be speculated that the binding energy between quarks is just a case where the energy of quantum entanglement equals the energy of the angular velocity of the quarks. So no matter how much energy one puts into a proton that energy divides equally between quantum entanglement energy and the energy of each quarks spin velocity. It would explain a lot about the origin of E=mc^2. Half of the energy in the formation of protons in the first microseconds of the universe occurred exactly at c, i.e.1/2 mv^2 = 1/2mc^2. This is the kinetic energy of the spin angular momentum of quarks. The other half of the energy, also equaling 1/2mc^2, equals the energy involved in quantum entanglement. So no matter how much energy you put into a proton that energy will divide equally between the magnitude of the spin angular velocity and the quantum entanglement energy and quantum entanglement will continue to rigidly confine the quarks.

I think people are starting to wake up to the fact that quantum entanglement plays a part in forming mass in all composite particles. And single photons are the only particles that are not composite particles and thus have no mass. However they do have energy so the 'm' in the kinetic energy of quarks but still be their energy but not in the "mass" sense. But even they can acquire mass through entanglement with other photons.

Eric

 

[ZapperZ]

I, myself don't think that quantum entanglement can be considered as something relative to the way that it is measured. It might have been an open question before the vast experimental evidence has built up, but I don't think it can be said anymore. Entanglement is not an "interpretative" event in that respect. And measurement only nails the quantum state of each of entangled composite particles at the instant it is measured.

I think you brought up a very interesting point about composite particles. This is the heart of the phenomena. It has only very recently been broadly realized that entanglement is not a rare event but probably plays a part in all particles that are made from composite particles. In this sense the assymptotic freedom of quarks in a proton could be considered just another aspect of quantum entanglement. In this special case it might be speculated that the binding energy between quarks is just a case where the energy of quantum entanglement equals the energy of the angular velocity of the quarks. So no matter how much energy one puts into a proton that energy divides equally between quantum entanglement energy and the energy of each quarks spin velocity. It would explain a lot about the origin of E=mc^2. Half of the energy in the formation of protons in the first microseconds of the universe occurred exactly at c, i.e.1/2 mv^2 = 1/2mc^2. This is the kinetic energy of the spin angular momentum of quarks. The other half of the energy, also equaling 1/2mc^2, equals the energy involved in quantum entanglement. So no matter how much energy you put into a proton that energy will divide equally between the magnitude of the spin angular velocity and the quantum entanglement energy and quantum entanglement will continue to rigidly confine the quarks.

I think people are starting to wake up to the fact that quantum entanglement plays a part in forming mass in all composite particles. And single photons are the only particles that are not composite particles and thus have no mass. However they do have energy so the 'm' in the kinetic energy of quarks but still be their energy but not in the "mass" sense. But even they can acquire mass through entanglement with other photons.

Eric

Please re-read the PF Guidelines that you have explicitly agreed to. Pay particular attention to speculative personal theories. Your posts might be deleted and you will be ask to submit your "theories" to the Independent Research forum.

Zz.

 

[DrChinese]

...If Einstein himself proposed a theory 5 years earlier in which non-locality of cause and effect could possibly happen then it could be said that what Einstein was more properly saying in the EPR paper is that quantum entanglement can exist, but that we just need to fill in our picture of physics in a way that it makes sense. It's interesting to me that so many physicists seem to ignore the title of the EPR paper: "Can The Quantum Mechanical Description of Physical Reality Be Considered Complete?"

It almost seems that the physics community has just built this straw man of "local variables" that Bell produced to show Einstein didn't know what he was talking about. Clearly he did and the title of the paper neatly summed it up what he was "really" saying.

I'd still be interested in any responses to what I said above. I realize what I'm saying maybe a little off in right field to some of you but I really think Bell's inequality is just a starting point for understanding quantum entanglement. It just shows that the non-locality of correlative effects exist but in no way addresses Einstein's real question. I think it misses the forest for the trees. Conversely, I think the EPR paper was concentrating on the forest - something which is done rarely in physics, even today. I promise I won't talk about my own ideas about QE if I can just get you guys to engage on this point.

Eric

Einstein did not believe in non-locality. As the inventor of relativity, he essentially took locality as a given.

As to the title of the great EPR paper: perhaps you should refresh yourself with EPR's primary conclusion, which was proven and is generally accepted: If Quantum Mechanics is complete (i.e. there is no better description of the state of the system - my words), then there cannot be simultaneous reality to non-commuting operators. The contranegative is also true: if there is simultaneous reality to non-commuting operators, then Quantum Mechanics is incomplete.

EPR then speculates as follows: a) that there is simultaneous reality to non-commuting operators MUST be true; therefore QM is incomplete; or b) there exists non-local forces (spooky action at a distance). Since Einstein did not believe b) was true, this shows that he believed in a) and ultimately that the predictions of QM could not hold in this case.

This speculation is what ultimately led to Bell's paper, which showed that: if QM is incomplete but otherwise correct in its predictions, then there must exist non-local forces. I would not call Bell's assumptions "straw men". Although some have referred to them as "naive realism" and/or "naive locality", they are taken plenty seriously today. And certainly so by Einstein, although he of course never saw Bell's work. I am quite sure he would have appreciated what Bell did.

 

[exeric]

Please re-read the PF Guidelines that you have explicitly agreed to. Pay particular attention to speculative personal theories. Your posts might be deleted and you will be ask to submit your "theories" to the Independent Research forum.

Zz.

Why don't you let people pick apart what I've said before you delete it. And if people wish to pick apart what I've said it is always a good idea to first debate the concepts presented by the messenger than to debate the quality of the messenger himself. That is one of the first principles of open debate. I've done substantial work on quantum entanglement and do not wish to overpromote myself on this. I can email you privately what my background on this is if you are interested.

 

[ZapperZ]

Why don't you let people pick apart what I've said before you delete it. And if people wish to pick apart what I've said it is always a good idea to first debate the concepts presented by the messenger than to debate the quality of the messenger himself. That is one of the first principles of open debate. I've done substantial work on quantum entanglement and do not wish to overpromote myself on this. I can email you privately what my background on this is if you are interested.

You could be a Nobel Prize winner, and we will still enforce the Guidelines. You know what you are getting yourself into from the very beginning.

If you wish to have people pick apart your ideas, that is exactly that the Independent Research forum is for. We apply this rule to everyone, you included.

This forum is not the place for you to work out your personal theory.

Zz.

 

[exeric]

You could be a Nobel Prize winner, and we will still enforce the Guidelines. You know what you are getting yourself into from the very beginning.

If you wish to have people pick apart your ideas, that is exactly that the Independent Research forum is for. We apply this rule to everyone, you included.

This forum is not the place for you to work out your personal theory.

Zz.

Ok, delete those posts. But don't delete my first two posts to this thread. There is nothing wrong with them being placed here. I think its a very fine line between trying to advance knowledge by challenging accepted theory and quarantining new ideas to a "safe" place, where they can be ignored. I think it is something to be concerned about, don't you? Science cannot be entirely extricated from human impulses for overt social control but it should be at least recognized that it also happens in science just as in non-scientific areas.

Eric

 

[exeric]

What on Earth are you talking about? You first say you have a couple questions – but give none, only opinions. Just what is “this point” ??
And then what do you think Einstein's real question was, if not to claim QM cannot be complete as QM claims itself to be, as it calls for reality to be non-local.

It's hard to know where to begin. The most blatant problem with quantum entanglement is in asking where the energy for quantum entanglement comes from. Do you actually think conservation of energy is not involved in the quantum entanglement process? If you accept that "free lunch" premise then I'm sorry, but you've already drunk the quantum mechanical kool-aid. This is the real essence Einstein was getting at in the question: "Can the quantum mechanical description of physical reality be considered complete?" There are no free lunches and Einstein was just stating the worst example of non-conservation of energy in the EPR paper, which is the energy involved in quantum entanglement. What's so difficult in understanding this is a problem?

Eric

 

[ZapperZ]

Ok, delete those posts. But don't delete my first two posts to this thread. There is nothing wrong with them being placed here. I think its a very fine line between trying to advance knowledge by challenging accepted theory and quarantining new ideas to a "safe" place, where they can be ignored. I think it is something to be concerned about, don't you? Science cannot be entirely extricated from human impulses for overt social control but it should be at least recognized that it also happens in science just as in non-scientific areas.

Eric

Since when is the advancement of science done on an open internet physics forum?

Again, you AGREED to abide by OUR rules when you signed on. You are more than welcome to 'advance science' elsewhere if you don't care for the guidelines.

Zz.

 

[ttn]

As to the title of the great EPR paper: perhaps you should refresh yourself with EPR's primary conclusion, which was proven and is generally accepted: If Quantum Mechanics is complete (i.e. there is no better description of the state of the system - my words), then there cannot be simultaneous reality to non-commuting operators. The contranegative is also true: if there is simultaneous reality to non-commuting operators, then Quantum Mechanics is incomplete.

I've been over this with you a million times before, but... for the benefit of any intelligent lurkers... the above represents a failure to grasp what is at issue in the EPR argument, and what they were trying to argue for. Dr C suggests that the thrust of the EPR paper was to argue for the following statement: if QM is complete, then there cannot be simultaneous reality to non-commuting operators/observables.

But that's not even the kind of thing one needs to argue for. It's simply a *definition* of completeness -- or more specifically, it's a clear litmus test for completeness in the context of a theory which simply doesn't *allow* the assignment of simultaneous definite values to non-commuting operators. It's just a given that, in orthodox QM, you can't do this. And so, to whatever extent, out there in physical reality, such observables *do* possesses simultaneous definite values, then orthodox QM is not complete.

So not only is that not the main thing EPR are arguing for, it's not the kind of thing one needs to argue for at all. To understand what the statement means is to see it as obviously true. The hard part is to construct some kind of argument that, in fact, out there in physical reality, such observables (i.e., those corresponding respectively to non-commuting operators) do possesses simultaneous definite values. And Dr C seems to completely miss that there is something like this argument in EPR, though, admittedly, it is hard to understand because of the way Podolsky wrote the manuscript. (Einstein didn't see the final draft and got mad that Podolsky had "buried" the main argument.) But now we know what Einstein had in mind. The argument was fundamentally based on *locality*. See "Einstein's Boxes" for further details.

EPR then speculates as follows: a) that there is simultaneous reality to non-commuting operators MUST be true; therefore QM is incomplete;

This is a ridiculous piece of trash. As a fan of Einstein I'm personally insulted that someone would publicly suggest that this was the EPR argument. I mean, come on. Einstein "speculates" (i.e., just makes up arbitrarily because he feels like it, not based on any argument) that observables corresponding to non-commuting operators "MUST" have simultaneous definite values? He just makes it up? I mean, please. It's a disgusting insult to the greatest physicist ever. Anyone who has a shred of respect for the great man should realize, if they think this was the argument, that maybe they just haven't *understood* the argument yet... and so they should go back and do some homework to find out what Einstein actually thought, rather than spread vicious lies and confusions that make Einstein sound like a moron.

or b) there exists non-local forces (spooky action at a distance).

Look, the argument is that *unless* one accepts spooky nonlocal forces, one must posit certain elements of reality. There's an actual *argument* there. If you haven't understood the argument, go back and study the issue some more. But don't keep spouting this nonsense that Einstein just arbitrarily "speculated" that it was a or b... Sheesh.

Since Einstein did not believe b) was true, this shows that he believed in a) and ultimately that the predictions of QM could not hold in this case.

Where did Einstein ever say that "the predictions of QM could not hold"? Actually the whole EPR argument (or his Boxes version) is premised on the predictions of QM being true. The whole argument is that the only way to explain certain correlations (namely, those *predicted by QM*) LOCALLY is to posit certain "hidden variables".

This speculation is what ultimately led to Bell's paper, which showed that: if QM is incomplete but otherwise correct in its predictions, then there must exist non-local forces.

You misunderstand this as well. One needn't assume that "QM is incomplete" in order to derive a Bell type inequality. The inequality follows from locality (a certain mathematically precise definition thereof which Bell first articulated) alone. That's it. Of course, it is possible to get a Bell inequality by first assuming certain hidden variables (and locality). But this doesn't change what I just said, since the existence of those hidden variables is itself a logical consequence of the locality assumption. That, as Bell points out repeatedly in his papers, is the EPR argument. Locality *requires* those hidden variables. So if Bell assumes them (and sometimes he does, but not always and it isn't logically necessary) it doesn't matter one way or the other. Either way, the inequality follows from Locality alone. The only question is whether one gets there in one step or two.

I don't expect to change your mind on any of this since I've tried so many times before and failed completely. But I can't in good conscience sit here and watch you disgustingly pervert these beautiful arguments. Not in front of what might (for all I know) be innocent children.

 

[RandallB]

EPR then speculates as follows: a) that there is simultaneous reality to non-commuting operators MUST be true; therefore QM is incomplete; or b) there exists non-local forces (spooky action at a distance). Since Einstein did not believe b) was true, this shows that he believed in a) and ultimately that the predictions of QM could not hold in this case.

I’m sorry tnn I just don’t see where this is an insult to Einstein any more than calling HV theories a belief in "naive locality / realism". It true and there is nothing wrong with that – it’s just not likely a correct view of actual reality based on testing so far.

Maybe using the word asserts instead speculates would help. I’ll sleep on it and reread your point in the AM.

 

[exeric]

Since when is the advancement of science done on an open internet physics forum?

Again, you AGREED to abide by OUR rules when you signed on. You are more than welcome to 'advance science' elsewhere if you don't care for the guidelines.

Zz.

I thought I said you could delete the post involving quantum entanglement in protons. Do you want to argue with me now by projecting on to me that I didn't accept that? I did.

Are you annoyed because I accepted it with protest? Well, then be annoyed. I'm annoyed too. But I'm not threatening to kick you off like you are threatening me. I can live with annoyance. I guess you can't.

Hazzard the thought that we would EVER want to think deeply about science and not just accept the status quo.

Eric

 

[lalbatros]

Doc Al,
ZapperZ,
Dear All,

I don't understand this part. How do you separate out, for example

$|\Psi> = |up>_1|down>_2 + |down>_1|up>_2$

There are no unitary transformation to a different basis that you can do that separate them out, are there?

Would it not be possible to take

$|\Psi>$

as a basis vector and build the space by orthogonality around it?

I know that doing this would not only mix the spin part of the state but also the particle part. But why would that be a problem? Maybe because the particle state IS the preferred "frame of reference" ? If I consider photons as an exemple, should such a photon-mix state be less preferred?

Michel

 

[ZapperZ]

Doc Al,
ZapperZ,
Dear All,



Would it not be possible to take

$|\Psi>$

as a basis vector and build the space by orthogonality around it?

Then show me how you would do that. How do you separate out each of the ket vectors.

Zz.

 

[DrChinese]

I've been over this with you a million times before, but... for the benefit of any intelligent lurkers...

1. But that's not even the kind of thing one needs to argue for. It's simply a *definition* of completeness -- or more specifically, it's a clear litmus test for completeness in the context of a theory which simply doesn't *allow* the assignment of simultaneous definite values to non-commuting operators. It's just a given that, in orthodox QM, you can't do this. And so, to whatever extent, out there in physical reality, such observables *do* possesses simultaneous definite values, then orthodox QM is not complete.

2. This is a ridiculous piece of trash. As a fan of Einstein I'm personally insulted that someone would publicly suggest that this was the EPR argument. I mean, come on. Einstein "speculates" (i.e., just makes up arbitrarily because he feels like it, not based on any argument) that observables corresponding to non-commuting operators "MUST" have simultaneous definite values? He just makes it up?

3. Look, the argument is that *unless* one accepts spooky nonlocal forces, one must posit certain elements of reality. There's an actual *argument* there.

4. Where did Einstein ever say that "the predictions of QM could not hold"?

The paper says exactly what I say, it is you that brings in discussion from after EPR.

1. Wrong! It may be the definition today, but hardly at the time. In effect, EPR is attacking the HUP and is connecting the HUP to the completeness argument. It's a great piece of work, and I think it stands the test of time.

2. I didn't insult Einstein, would never do that. But I did accurately relate the EPR arguments. There is speculation in the last sentence of the paper, which sums it up: "We believe, however, that such a theory [local realistic] is possible." And clearly, the statement 2 sentences previously: "No reasonable definition of reality could be expected to permit this" is completely speculative. QED.

3. They are trying to make the argument that it is an either/or, I have no disagreement with that. There is non-locality on one side (expressed by the statement "there is no longer any interaction between the two parts"), and something else on the other - whatever you want to call it. I specifically pointed this out to you in my post, see my a) and b) !

4. Wigner said in the 30's that Einstein believed "...that quantum mechanics has a limited validity, just as the basic ideas of Newton were..." I can't find a more suitable quote at this time, but I certainly don't believe for one moment that Einstein ever believe that any apparently non-local effect would be discovered from space-like particles which had interacted in the past. Of course he also did not have the benefit of Bell to make this dilemma more clear.

 

[ueit]

First off, in the context you used "it" for was not for the person Bell you were referring to the "Bell Theorem" or its application.

OK, my mistake.

And just declaring the "assumption that we live in a local deterministic universe" does show anything beyond establishing a point of faith maybe.

It's not about faith, it's a hypothesis, and this hypothesis cannot be proven wrong by Bell's theorem. This is all I'm saying. I do not claim that it is true. It may be, we don't know yet.

And GR has not be shown to be "local" - plenty to read by Smolin on the requirement for indeterminate background for GR (Non-local IMO) that has not been disproved to any reasonable satisfaction.

I've never seriously studied GR so you may be right, but can you be more specific about this? Gravity travels at c, so at least GR is not non-local in the way Newtonian gravity was. What exactly is that travels at infinite velocities in GR?

And the idea that when setting of two space like separated wheels (detector switches) we a powerless to use free will or judgment to set them differently that what the Big Bang preset deterministic universe has already decided what we will do, is just pointless. Talk about an un-testable theory - it demands that we can only know a proof for it IF it has been predetermined for us to learn it.

Free will is a very weak hypothesis, in fact is almost certainly wrong even if QM is fundamentally random, because the neural activity is in the classical regime.

The absence of free will is a logical consequence of determinism unless you believe that humans are somehow above nature (immaterial souls?).

I don't think that a deterministic theory is untestable. May be "it has been predetermined for us" to test it.

If you understand what LOCAL means, you would recognize this as a Non-Local Local theory. It is only local within itself as it reaches out to its preset deterministic values to explain correlations. Just like non-local BM and MWI are local within those theories, using invisible guide-waves and multi-dimensional extended realities to explain correlations within their theory.

A deterministic universe (classical or non) is not a Local (Bell Local) theory, and if you want to apply Occum's to the Non-locals this one IMO falls to the bottom of that list.

I don't propose any "extended realities". Think at those wheels as the known particles. For example, it may be that BM could find a local explanation just like Newtonian gravity found one in GR (I know, you object to that but you should at least agree that gravity does not propagate at an infinite velocity in GR).

Personally I think realty is local and real does not need some kind of strange extended reality; but that is just an opinion, I don't go around declaring it as a fact.

This is my opinion too. And I don't claim it is a fact either. The only claim I make is that Bell's theory doesn't disqualify local realistic theories from the start. That is, it is logically possible that a local-realistic theory underlies QM. And I think we agree on that.

But unlike yours I know exactly the tool that is required to turn my opinion to fact, and that is the Bell Theorem itself. And it only need do so once, and all the non-locals will fall including yours. But no individual Non-local theory even has a tool that has an expectation of excluding other theories.

I don't propose any non-local theory, in fact I'm not capable of proposing any theory to revolutionize physics. I only try to point some logical mistakes frequently done even by experienced physicists when interpreting Bell's theorem.

So if you cannot even produce a tool that might provide a proof of your theory at least state it as an opinion or personal preference and do not demand it be accepted as a simple fact.

I didn't intended for my analogies to be taken as "theories". They are only examples of how non-local correlations could be simulated in a local theory.

 

[ttn]

The only claim I make is that Bell's theory doesn't disqualify local realistic theories from the start. That is, it is logically possible that a local-realistic theory underlies QM. And I think we agree on that.

Bell's theorem has nothing to do with 'realism', but it does prove that no local theory can agree with experiment. You have a "hunch" that says otherwise... but is this actually based on anything? For example, can you tell us exactly where Bell went wrong in his reasoning? He quite unambiguously states -- and I have studied his work in detail and believe he is right -- that the theorem proves that no local theory can be viable. The argument -- the detailed proof of this conclusion -- is right there in his papers. So the burden is clearly on you to justify your speculation that he was wrong. Otherwise, you're just some schmuck spouting BS on an internet forum.

I only try to point some logical mistakes frequently done even by experienced physicists when interpreting Bell's theorem.

So point to them.

 

[RandallB]

"assumption that we live in a local deterministic universe"
It's not about faith, it's a hypothesis, and this hypothesis cannot be proven wrong by Bell's theorem. This is all I'm saying. I do not claim that it is true. It may be, we don't know yet.

Of course Bell doesn’t address deterministic it only address Local vs. Non-local. And deterministic theories are non-local

I've never seriously studied GR so you may be right, but can you be more specific about this? Gravity travels at c, so at least GR is not non-local in the way Newtonian gravity was. What exactly is that travels at infinite velocities in GR?

I already gave you Smolin – 3 books and lots of papers; plus READ though the forum below this one (SR & GR) that more than enough to keep you out of trouble till to start to understand enough to talk about GR – take your time and think as you go – remember it took Einstein 10 years – you think you should get it in ten minuets?

Plus, what do infinite velocities have to do with anything? Newton was very clear about gravity and he never called for infinite velocity, if someone says he did ask them in which Newton Book, Issue, Chapter, Page and Line he did.

….. it is logically possible that a local-realistic theory underlies QM. And I think we agree on that.

NO we don’t agree because you’re saying that locality could be a correct underlying part of a correct and complete QM – you do not understand Bell-local here. I agree or I should say QM agrees with me, including DrC IMO, that IF (read it again IF) locality is shown to be true, at that instant anyone that understands QM will admit QM is wrong – The Whole Point Is - the evidence so far is for a Non-Local World.

I don't propose any non-local theory …….

But you DO! A classical deterministic is NOT BELL LOCAL.
Bell Local means that as each of the series of individual photons the meet up with the PDC to interact with it there are only the local inputs of the PDC and the one Photon that creates two Photons, only local variables can exist in each of them based on all the conservation of etc. etc. There is nothing to keep the two connected they depart that local area to how ever far away taking only Local Variables with them.
The results found at the later distant test say we don’t know all those variables. Plus even no unknown hidden one we can come up with will explain is the results seen there so far. Thus – if this conclusion is correct then our common sense realistic ideas of reality are wrong; that is the correct reality is non-local and our comfy local realist inclinations are just wrong. Bell can say no more than this – period!

Sure the PDC and each of those photons have a history – BUT to “extend ancient reality” of them to the past reality of any possible measuring devise they may encounter. Even if the have to go all the way back to the big bang, AND expect that “extended reality” to be informative enough as to cause the correlations we see. And sure full and complete determinism would do that but it sure is not BELL LOCAL! And IMO it is a ridiculous hypothesis. The Non-local BM and MWI theories (and others) with realities that add guide waves and extra dimensions to the “realistic” are far more sensible than any deterministic theory no matter how many dimensions it may or may not have.

SO PLEASE take this, no free will, deterministic “science” to the Philosophical forums, just use the menu to get there.

 

[NateTG]

And sure full and complete determinism would do that but it sure is not BELL LOCAL! And IMO it is a ridiculous hypothesis. The Non-local BM and MWI theories (and others) with realities that add guide waves and extra dimensions to the “realistic” are far more sensible than any deterministic theory no matter how many dimensions it may or may not have.

I almost don't have the heart to point out that MWI is, in fact, an example of 'full and complete determinism' which just uses a slighly different form of bookkeeping. After all, from the point of view of the interpreation, any time a measurement takes place, all possible results occur even if the observer (after measurement observers) must individually go with each of these results. Really, the difference between this, and a 'braindead' all measurements are determined in advance according to rules x, y and z approach is that one is more frequentist while the other is more baesian.

 

[RandallB]

I almost don't have the heart to point out that MWI is, in fact, an example of 'full and complete determinism' which just uses a slighly different form of bookkeeping.

I disagree; it seems easy to me that a MWI view can maintain free will as it will only serve to limit the MW’s to those uncertainties within the bounds of free will choices. Be those choices made by an amoeba or some other free will form.
Sure a more restrictive interpretation may be defined, especially if one desires to describe MWI as brain-dead.
But, as I’m not a fan of MWI, I have not right to demand that it be interpreted as using 'full and complete determinism' just so I can discard the theory; without my offering some proof that it must be thought of that way and I cannot.

As long as it is used to create extended HV’s in a definition of “local” that simply extends beyond our 3D world into some extra-dimensional MW view of reality I cannot refute MWI’s ability to resolve entanglement its own non-local manor.

BUT, I don’t accept that view or any non-local view until it can create an experiment that can produce convincing results that only that view can explain. No non-local has and if QM is correct none ever will, including QM.

 

[RandallB]

Bell's theorem has nothing to do with 'realism',

tnn
I disagree as since the ‘realism’ or reality expected by a “local realist” (like me) is not just local but “Bell Local”. To the extent that Bell Tests have demonstrated that expectation (mine) is wrong; it means that the correct reality is something other than 'realism' expected by a “local realist”.

I’ve tried to understand the conflict between you and DrC, but at the end of each of your respective points to me you both seem to end up at the same place.

- EPR and Bell as the modern distillation of it can looks for LHV’s in an effort to decide between Local vs. Non-Local. It can not confirm anyone version of a Theory, Bell tests can only comment on the local vs. non-local issue.

- QM claims to be complete; Complete in that no physical explanation of reality can provide greater predictive ability than the statistical “shut-up and calculate” style of QM.

- Other Non-Locals (BM, WMI, M, Strings etc.) claim to have a ‘good’ explanation, BUT offer no experiments that exceed the ability of QM to make predictions.

The only place I see conflict might be in an expectation that Bell could prove a theory, and that is clearly wrong for either side as I think we all agree EPR-BELL can only address Local vs. Non-Local. It will take something other than Bell in some experiment to select between QM, MWI, BM, etc.

For QM the bad news is there can be no experiment ever that can affirmatively prove the claim of completeness. For such a positive proof to be found and made it could only do so by revealing something new QM had not already accounted for, thus showing itself to have been incomplete! That is the claim of QM is even if something like MWI or BM is correct – it will be impossible to every find a way to prove it.

For the other Non-Locals (MWI, BM, etc) they can hold out hope that something someday may prove their case, by showing us something that QM cannot. But no one has yet proposed any experiment or prediction of an event that can only be explained by their theory.

In fact there has been only one theories that has been able to even propose an idea or experiment capable of proving itself correct. That would be the Local Realist and the experiment, EPR-Bell; as both Einstein and J. Bell hoped it would make known the unknown hidden variable that must exist for the Local Realist”. BUT, Part of the risk of putting forward such an experiment is that it may just falsify you own ideas; which seems to be the case so far.

 

[ttn]

tnn
- QM claims to be complete; Complete in that no physical explanation of reality can provide greater predictive ability than the statistical “shut-up and calculate” style of QM.

Except that isn't what "complete" actually means.

- Other Non-Locals (BM, WMI, M, Strings etc.) claim to have a ‘good’ explanation, BUT offer no experiments that exceed the ability of QM to make predictions.

First, MWI i s not non-local. Second, how is it valid to ever say something like "BM offers no experiments that exceed the ability of QM to make predictions."? The two theories make the same predictions. So one can just as correctly say "QM offers no experiments that exceed the ability of BM to make predictions... so to hell with QM". Get it? There are two theories. They make the same predictions. So it is completely invalid to dismiss one of them merely on the grounds that it just reproduces the predictions of the other. In fact, people who make that argument are using it as a smokescreen to hide the fact that they have some kind of indefensible bias against one of the theories.

The only place I see conflict might be in an expectation that Bell could prove a theory, and that is clearly wrong for either side as I think we all agree EPR-BELL can only address Local vs. Non-Local.

Not to speak for Dr C, but I'm pretty sure he doesn't agree with that. He's argued with me all over the place here over the years that one gets to choose either to reject locality or ... some other thing.

It will take something other than Bell in some experiment to select between QM, MWI, BM, etc.

Of course. Who ever said that Bell's theorem proves one of these right as against the others?

For QM the bad news is there can be no experiment ever that can affirmatively prove the claim of completeness. For such a positive proof to be found and made it could only do so by revealing something new QM had not already accounted for, thus showing itself to have been incomplete! That is the claim of QM is even if something like MWI or BM is correct – it will be impossible to every find a way to prove it.

That's one piece of bad news, yes. But there is also the measurement problem, the fact that it is a nonlocal theory, etc...

For the other Non-Locals (MWI, BM, etc) they can hold out hope that something someday may prove their case, by showing us something that QM cannot. But no one has yet proposed any experiment or prediction of an event that can only be explained by their theory.

In fact there has been only one theories that has been able to even propose an idea or experiment capable of proving itself correct. That would be the Local Realist and the experiment, EPR-Bell; as both Einstein and J. Bell hoped it would make known the unknown hidden variable that must exist for the Local Realist”. BUT, Part of the risk of putting forward such an experiment is that it may just falsify you own ideas; which seems to be the case so far.

"Local realist" is not a theory. And as I said before, "realist" (or "realism" or whatever) has no place in any of these discussions anyway. Bell's theorem proves that any empirically viable theory has to be nonlocal. That's it. Anyone who thinks "realism" is also at play better explain what they mean by that term.

 

[DrChinese]

1. Not to speak for Dr C, but I'm pretty sure he doesn't agree with that. He's argued with me all over the place here over the years that one gets to choose either to reject locality or ... some other thing.

2. Anyone who thinks "realism" is also at play better explain what they mean by that term.

1. You are so correct!

2. Realism is simply another word for the completeness doctrine, really as EPR defines it. This can be expressed many different ways as words (and they are just words):

a) Non-realistic = QM is Complete = No greater description of state possible = Observer Dependence.

b) Realistic = QM is Incomplete = Hidden variables = Observer Independent Reality

In the QM formalism, I see this as saying that the state function fundamentally obeys the HUP, so statistical outcomes are dependent on what is observed.

 

[NateTG]

tnn
I disagree as since the ‘realism’ or reality expected by a “local realist” (like me) is not just local but “Bell Local”. To the extent that Bell Tests have demonstrated that expectation (mine) is wrong; it means that the correct reality is something other than 'realism' expected by a “local realist”.

In some sense, 'Bell Test' is a misnomer since Bell's Theorem does, in fact, involve untestable assumptions such as Bell Locality and realism.

- QM claims to be complete; Complete in that no physical explanation of reality can provide greater predictive ability than the statistical “shut-up and calculate” style of QM.

- Other Non-Locals (BM, WMI, M, Strings etc.) claim to have a ‘good’ explanation, BUT offer no experiments that exceed the ability of QM to make predictions.

From the Stanford Encyclopedia of Philosophy:
http://plato.stanford.edu/entries/qm-bohm/

It is perhaps worth mentioning that despite the empirical equivalence between Bohmian mechanics and orthodox quantum theory, there are a variety of experiments and experimental issues that don't fit comfortably within the standard quantum formalism but are easily handled by Bohmian mechanics. Among these are dwell and tunneling times (Leavens 1996), escape times and escape positions (Daumer et al. 1997a), scattering theory (Dürr et al., 2000), and quantum chaos (Cushing 1994, Dürr et al., 1992a).

 

[exeric]

tnn
In fact there has been only one theories that has been able to even propose an idea or experiment capable of proving itself correct. That would be the Local Realist and the experiment, EPR-Bell; as both Einstein and J. Bell hoped it would make known the unknown hidden variable that must exist for the Local Realist”. BUT, Part of the risk of putting forward such an experiment is that it may just falsify you own ideas; which seems to be the case so far.

You are wrong. I can think of at least another.

Eric

 

[wm]

2. Realism is simply another word for the completeness doctrine, really as EPR defines it. This can be expressed many different ways as words (and they are just words):

a) Non-realistic = QM is Complete = No greater description of state possible = Observer Dependence.

b) Realistic = QM is Incomplete = Hidden variables = Observer Independent Reality

In the QM formalism, I see this as saying that the state function fundamentally obeys the HUP, so statistical outcomes are dependent on what is observed.

Is there a problem with the middle-way?

c) Realistic = QM is Incomplete = Hidden variables = Observer Dependent Reality = the particular hidden variable exposed is dependent on the observer's choice of ''measurement''.