How do particles become entangled?

[Eye_in_the_Sky]

I do think that your argument embodies a reformulated version of Bell which ends up losing a little something in the process.

I agree that my argument does not follow the structure of that given by Bell. (In my argument, I used as the "starting point": 'pre-determined' or not 'pre-determined'. Bell's "starting point" is simply 'locality' (according to Einstein's definition). Originally, I had specific reasons for choosing the "starting point" as I did, but now I am not so sure that that was entirely necessary. Moreover, I am now suspecting that the first part of my argument (labeled "1)", i.e. not 'pre-determined') is less trivial than I thought it to be.)

Let us therefore consider Bell's argument exactly as he originally presented it. You are saying that in that formulation there is a "reality", or a "realistic-ness", assumption of some kind being made. You have also indicated one implication of such an assumption:

Reality=Bell's condition that the chance of an outcome is within the range of 0 to 1.

On the face of it, to negate such a proposition is absurd ... isn't it?

Tell me, is this the only assumption of Bell which physicists consider negating on account of a not-"reality" proposal?

 

[DrChinese]

Let us therefore consider Bell's argument exactly as he originally presented it. You are saying that in that formulation there is a "reality", or a "realistic-ness", assumption of some kind being made. You have also indicated one implication of such an assumption:

Reality=Bell's condition that the chance of an outcome is within the range of 0 to 1.

On the face of it, to negate such a proposition is absurd ... isn't it?

Tell me, is this the only assumption of Bell which physicists consider negating on account of a not-"reality" proposal?

I agree that on the face of it, the proposition is absurd. But further investigation shows it is far from absurd, and that is part of what makes QM so powerful (as you know).

If you look at the outcomes, you will see that certain combinations are actually predicted (by QM) to have negative probabilities, flying in the face of the "obviously reasonable" counter-position of reality shown above. QM makes plenty of similar counter-intuitive predictions, all of which have so far been pretty well verified. Aspect verified this particular one in his famous experiments.

The "loophole" from Bell's Theorem was that a non-local theory could also account for the observed behavior. So there is your option, and you are free to choose it if you prefer.

But there are other tests of QM which show similar negative probabilities. For example, take the reflection of light off a mirror from a source to an intensity detector. There are many paths to the detector that provide negative intensity, in violation of common sense. If you prevent the light from taking those paths (such as via etching the mirror in appropriate spots), the detected intensity increases. This is because the "negative" probability cases are being excluded, which cause the sum of the various path intensities to the detector to increase.

So ultimately, what is "reasonable" to one person may not be reasonable to another. Is non-locaity more reasonable than negative probabilities?

You can also map the hidden variable concept to the negative probabilities in the Bell paper. It is the manipulation of the local hidden variable (your "predetermined") outcomes that directly leads to the negative probabilities in the first place. Another way to say it is that certain combinations are suppressed. The difficulties lie in the words used to describe it more than the actual underlying formalism.

 

[Caroline Thompson]

"Negative probabilities" don't happen either

If you look at the outcomes, you will see that certain combinations are actually predicted (by QM) to have negative probabilities, flying in the face of the "obviously reasonable" counter-position of reality shown above. QM makes plenty of similar counter-intuitive predictions, all of which have so far been pretty well verified. Aspect verified this particular one in his famous experiments.

"Pretty well" is, in this instance, surely not good enough! We're talking about a claim that something happens that is not merely (in my view) "counterintuitive" but actually "impossible". If such a thing is to be believed we need incontrovertible evidence, not experiments whose interpretation only backs the belief if you also accept a number of assumptions that are, to a local realist, simply not reasonable.

The "loophole" from Bell's Theorem was that a non-local theory could also account for the observed behavior. So there is your option, and you are free to choose it if you prefer.

Quite! [Perhaps I should have read a little further before reacting.]

But there are other tests of QM which show similar negative probabilities. For example, take the reflection of light off a mirror from a source to an intensity detector. There are many paths to the detector that provide negative intensity, in violation of common sense. If you prevent the light from taking those paths (such as via etching the mirror in appropriate spots), the detected intensity increases. This is because the "negative" probability cases are being excluded, which cause the sum of the various path intensities to the detector to increase.

I guess you've been reading Feynman's QED? But all the above is only a matter of interpretation, conducted by someone who is determined to believe that light consists of photons. Allow it to be pure waves and take account of the way interference works and these apparently negative intensities simply cease to exist. I wonder if you've read Mach's "Principles of Physical Optics"? It was first published around 1926 but has recently been re-published. It is written totally without any reference to photons or quantum theory and describes some quite amazing phenomena, all of which it explains using wave theory.

Caroline

 

[reilly]

Re Neg. Probs. (Dr. Chinese)

I agree that on the face of it, the proposition is absurd. But further investigation shows it is far from absurd, and that is part of what makes QM so powerful (as you know).

If you look at the outcomes, you will see that certain combinations are actually predicted (by QM) to have negative probabilities, flying in the face of the "obviously reasonable" counter-position of reality shown above. QM makes plenty of similar counter-intuitive predictions, all of which have so far been pretty well verified. Aspect verified this particular one in his famous experiments.

*************************************

I have a problem with negative probabilities. So, I'd be most grateful if you could provide details and chapter and verse on this idea. Thank you.

Regards,
Reilly Atkinson

 

[Caroline Thompson]

Caroline:
Thanks for your contribution to the thread. I guess many of us here are just trying to gain a better understanding of QM as it has been formulated and generally accepted. I understand the value of questioning the accepted dogma, but at least in my case I think I'll benefit more from gaining full understanting of the subject as presently understood and not to venture into concepts that deffy the commonly accepted theory. (at least not yet)
From all I know, and as Dr.Chinese clearly states, it appears that the tests (which you question) of Bell's inequalities sucessfully prove that locality or reality must give way. Your position is at odds with the accepted theory, and that must be the reason you didn't get a response. You might get better results by initiating a thread just on your proposal. Good luck.

Thanks. I may do some day (I'm not sure I'm allowed to at present) but for the time being will just carry on trying to make sure that people know what they are doing. It is entirely possible that there is no future in "entanglement" and hence no benefit (other than passing exams and/or impressing your friends) in trying to gain a "better understanding" of it.

I maintain that the future of physics lies in a return to the experimental evidence and intuitive approaches. This is as true of Einstein's theories as it is of quantum theory. I think the era in which we are content with mathematical algorithms that give us the right answer but leave us unsatisfied as regards understanding is drawing to a close. We can carry on using the algorithms but we need a new fundamental theory. So far as the experiments are concerned, there is no reason that this should not be entirely intuitive. It need not necessarily produce quantatitive predictions. Its sole purpose is to give us understanding of our universe, with local causes for everything.

Of two things I'm quite certain: the "true" physics of the future will model light as pure waves, with no "photons", and will not involve entanglement. All actual experiments can be explained using ordinary classical correlations, once you allow for the imperfections and the use of inappropriate versions of the Bell test.

Incidentally, unless allowance is made for the fact that real experiments have hidden variables that are "stochastic", only accounting for the probabilities of outcomes and not the outcomes themselves, rational interpretation of the results is impossible. Surely we all agree that when it comes to interpreting real experiments we need to use a model that covers what is actually done, not just an ideal situation dreamt up by theorists? Do have a look at my wikipedia pages (which DrChinese thinks should be somehow made to vanish!). Start with http://en.wikipedia.org/wiki/Bell's_Theorem and follow links to pages on the actual experiments and their loopholes.

Caroline
http://freespace.virgin.net/ch.thompson1/

 

[DrChinese]

Do have a look at my wikipedia pages (which DrChinese thinks should be somehow made to vanish!). Start with http://en.wikipedia.org/wiki/Bell's_Theorem and follow links to pages on the actual experiments and their loopholes.

Caroline
http://freespace.virgin.net/ch.thompson1/

Not vanish, just move to a page called Caroline's Theorem! :)

 

[alexepascual]

Caroline:
I can understand that DrChinese and you don't get along too well. On the other hand, from reading the posts it appears you might find some compatibility with Reilly's ideas. He also has expressed the opinion that quantum correlations are no different than classical correlations.
For the moment I'll accept the standard theory and try to find my own intuitive framework to make sense of it. With respect to the need for intuitive understanding, I see some compatibility between your position and mine. I think that quantum theory still needs to be modified or complemented until it becomes a better explanatory system. (I don't accept the Copenhagen interpretation) But given its success in predicting results (which you may question) , I would not question the validity of the equations.
But when it comes to finding a particular intuitive structure that makes the theory easier to make sense of, there is where you and I take different routes. I understand you are a local realist, which makes you reject anything that departs from classical thinking. I would say you are a conservative person in this respect, although being a conservative may appear as being a rebel nowadays when most people have accepted the revolutionary ideas and these don't appear revolutionary anymore.
I, on the other hand feel more confortable with an explanation that seems absurd to many people, and it is the "many worlds" interpretation. There is an apparent problem with this interpretation (there may be other problems too) and it is the proliferation of worlds. But I think perhaps a new version of this interpretation could turn out to eliminate that proliferation.
Paradoxically, I think in the end the "many worlds" interpretation is also a realist interpretation. Except that "reality" is not constrined to a 4-dimensional space-time but includes all possible outcomes. In this sense, I would say the many worlds interpretation is "super-realist" (that's my own idea).
But I can understand that such interpretation would be repulsive to you, because you are a positivist and would not accept the existence of other "worlds" which cannot be detected or measured directly.
I think Mach's ideas had an important role in the philosophy of science but are not always beneficial when taken to extremes. Remember that Mach didn't believe in the existence of atoms.
I think that some times it is advantageous to consider elements which are not directly measurable but which serve to organize the results of measurement in a more elegant way. Being the fact that nature appears to (most of the time) turn out to be pretty elegant, these non-observable constructs stand a chance of eventually becoming observable or at least so pervasive and necessary that could be considered as part of reality.
On the other hand, I think the original purpose of this thread was to explore the process of entanglement (whose existence you denny. For that reason, I think we continue to debate this controversial topic in the wrong place. You say you are not sure you can create a thread. As far as I know anybody who is a subscriber to the forum can create threads. You should have a button visible in your screen (when you are looking at the list of threads) that says "create new thread" or something similar.

 

[DrChinese]

I have a problem with negative probabilities. So, I'd be most grateful if you could provide details and chapter and verse on this idea. Thank you.

Regards,
Reilly Atkinson

It will probably take me a day or two :) to present it fully, but here is the starting point so you can see where I will be going:

a. 2 single channel detectors I will call Left and Right. The Left is set at angle A=67.5 degrees. The Right alternates between B=22.5 degrees and C=0 degrees. The selection of the angles is done to allow some sleight of hand with the math later. I will call it + if there is a detection, and a - if there is no detection. Efficiencies and actual experimental requirements are ignored as I am just trying to show the concepts involved.

b. In the Realistic case (the assumption of Realism, that the variables exist and have values independent of their observation), you could imagine that both B and C exist at the same time. Therefore, there are 8 combinations that must total to 100%. They are:

[1] A+ B+ C+
[2] A+ B+ C-
[3] A+ B- C+
[4] A+ B- C-
[5] A- B+ C+
[6] A- B+ C-
[7] A- B- C+
[8] A- B- C-

c. In the quantum world, 2 of the above cases are suppressed: [3] and [6]. The reason is that they don't actually exist as possibilities. B is the angle between A and C in my example, and B must always yield the same +/- value as either A or C. In these two cases, B is opposite to A and C. So in the Realistic scenario, [3]>=0 and [6]>=0 (and the sum of all 8 cases=1).

d. So what I have to do is to demonstrate that the quantum mechanical predictions for these 2 cases is actually less than zero. If I can do this, it will demonstrate a big conflict. The difficulty is that I have to do it using terms involving measurements of B or C, but not both at the same time. Can I do it? To be continued...

-DrC

 

[Caroline Thompson]

[1] A+ B+ C+
[2] A+ B+ C-
[3] A+ B- C+
[4] A+ B- C-
[5] A- B+ C+
[6] A- B+ C-
[7] A- B- C+
[8] A- B- C-

This setup looks very similar to the one used in http://en.wikipedia.org/wiki/Sakurai%27s_Bell_inequality
The page covers my interpretation of the Wigner-d'Espagnat inequality, which is alternatively covered by a quantum theorist at http://en.wikipedia.org/wiki/Wigner-d%27Espagnat_inequality . Your idea seems subtly different, but perhaps it would make your task easier to switch to this better-known case? Since the inequality violates local realism it would be expected to also produce negative probabilities if analysed in the manner suggested by Feynman in

Feynman, R P, Simulating Physics with Computers, International Journal of Theoretical Physics 21, 467-488 (1982).​

[I read this a very long time ago and don't guarantee anything!]

Caroline

 

[Caroline Thompson]

Not vanish, just move to a page called Caroline's Theorem! :)

Now that's not fair and you know it!

I discuss Bell's theorem in the spirit originally intended, though, not in the manner to which people have become accustomed. Bell was originally a realist. When experiments were found to (apparently) back quantum theory he was saddened. He said:

"So, for me, it is a pity that Einstein's idea does not work. The reasonable thing just does not work." [P Feyerabend "Historical Comments on Realism", p 194 of A Van der Merwe, F Selleri and G Tarozzi, “Bell's Theorem and the foundations of modern physics” (World Scientific, Singapore, 1992)]​

Caroline
http://freespace.virgin.net/ch.thompson1/

 

[Caroline Thompson]

Caroline:
I can understand that DrChinese and you don't get along too well.

[Actually we understand each other quite well, I think.]

On the other hand, from reading the posts it appears you might find some compatibility with Reilly's ideas. He also has expressed the opinion that quantum correlations are no different than classical correlations.

Thanks, I'll look him up.

Re your multiworlds ideas, you are quite right: I have no place for them in my world!

On the other hand, I think the original purpose of this thread was to explore the process of entanglement (whose existence you deny. For that reason, I think we continue to debate this controversial topic in the wrong place. You say you are not sure you can create a thread. As far as I know anybody who is a subscriber to the forum can create threads. You should have a button visible in your screen (when you are looking at the list of threads) that says "create new thread" or something similar.

Thanks for the advice, but I can't find that button. I have found, though, a comforting little note that says I have the right to create new threads. Some day I'm sure I'll find out how to do so!

Caroline

 

[DrChinese]

Now that's not fair and you know it!

I discuss Bell's theorem in the spirit originally intended, though, not in the manner to which people have become accustomed. Bell was originally a realist. When experiments were found to (apparently) back quantum theory he was saddened. He said:

"So, for me, it is a pity that Einstein's idea does not work. The reasonable thing just does not work." [P Feyerabend "Historical Comments on Realism", p 194 of A Van der Merwe, F Selleri and G Tarozzi, “Bell's Theorem and the foundations of modern physics” (World Scientific, Singapore, 1992)]​

Caroline
http://freespace.virgin.net/ch.thompson1/

Sorry, but I really don't think it is all that important whether Bell believed in local realism at various points in his life or not. His theorem holds great significance and I only wish that Einstein could have lived to see it.

As to the spirit of your Wikipedia presentation of Bell's work: I think you would be disingenuous if you said you were not aware of your presentation bias. Anyone familiar with his work will recognize the hand of a highly biased author. As I have said before, your anti-establishment bias is a good thing when it is properly disclosed. It is not fair to the less educated reader to mis-characterize your stand as commonly accepted science when it is not. That statement remains true even if you are eventually shown to be correct, because then your position would itself become mainstream. That is the way of science.

 

[freep2]

There is no space or matter in the univeres. Just Energy. Light=Energy. Thought= Energy.

 

[DrChinese]

I have a problem with negative probabilities. So, I'd be most grateful if you could provide details and chapter and verse on this idea. Thank you.

Regards,
Reilly Atkinson

I have pretty well completed my post in response, Reilly. I will be creating a separate thread to discuss this, no later than tomorrow. I think the result should be as straightforward as is possible, and the math is such that anyone can easily follow. I hope I don't bungle it :)

-DrC

 

[Caroline Thompson]

Sorry, but I really don't think it is all that important whether Bell believed in local realism at various points in his life or not. His theorem holds great significance and I only wish that Einstein could have lived to see it.

As to the spirit of your Wikipedia presentation of Bell's work: I think you would be disingenuous if you said you were not aware of your presentation bias. Anyone familiar with his work will recognize the hand of a highly biased author. As I have said before, your anti-establishment bias is a good thing when it is properly disclosed. It is not fair to the less educated reader to mis-characterize your stand as commonly accepted science when it is not. That statement remains true even if you are eventually shown to be correct, because then your position would itself become mainstream. That is the way of science.

See my response to your entry http://en.wikipedia.org/wiki/Talk:B...pson.27s_POV_and_Self_Promotion_in_this_topic.

I have never disguised my bias. In my opinion, as I think you know, it is unfair on the public to be told that quantum entanglement has been confirmed experimentally when this is not the case. Why, if it had been satisfactorily proven, would people still be trying to find "loophole-free" tests?

 

[caribou]

Here's a quote from Roland Omnes' book Understanding Quantum Theory:

An entangled state is a quantum superposition of two distinct physical systems. This is a very frequent situation because any composite system whose wave function is not simply a product of the wave functions of its components is entangled. The existence of these states is proclaimed by the Pauli principle, and in that sense, it is responsible for a host of physical properties from the hardness of a stone to the laser.

I consider the hardness of stones and the existence of lasers to be experimentally confirmed.

 

[DrChinese]

1. I have never disguised my bias.

2. In my opinion, as I think you know, it is unfair on the public to be told that quantum entanglement has been confirmed experimentally when this is not the case.

3. Why, if it had been satisfactorily proven, would people still be trying to find "loophole-free" tests?

1. Your participation in public forums usually omits reference to your unorthodox views, so I would say you disguise your bias by omission.

2. My opinion, shared by most scientists, is that it has been shown. Unambiguously.

3. The "closing of loopholes" is one of the most important elements of modern science, and in no way negates existing experiements or lessens their significance. That is why ever more elaborate tests of General Relativity are being performed today - even though GR is here to stay regardless of the outcome. Refinements and improvements to theory are good, even if minor.

 

[Caroline Thompson]

Here's a quote from Roland Omnes' book Understanding Quantum Theory:

An entangled state is a quantum superposition of two distinct physical systems. This is a very frequent situation because any composite system whose wave function is not simply a product of the wave functions of its components is entangled. The existence of these states is proclaimed by the Pauli principle, and in that sense, it is responsible for a host of physical properties from the hardness of a stone to the laser.

I consider the hardness of stones and the existence of lasers to be experimentally confirmed.

OK, so that was Omnes opinion and you are happy to go along with it. You may not be surprised to know that I do not and that I have my own ideas as to why stones are hard and how a laser works. See my web site: http://freespace.virgin.net/ch.thompson1/

Caroline

 

[Caroline Thompson]

1. Your participation in public forums usually omits reference to your unorthodox views, so I would say you disguise your bias by omission.

2. My opinion, shared by most scientists, is that it has been shown. Unambiguously.

3. The "closing of loopholes" is one of the most important elements of modern science, and in no way negates existing experiements or lessens their significance. That is why ever more elaborate tests of General Relativity are being performed today - even though GR is here to stay regardless of the outcome. Refinements and improvements to theory are good, even if minor.

Surely nobody is quite so naive as to think that local realists don't exist? Surely anyone can quickly deduce that I am one?

Re (2), on what is your opinion based? Perhaps it does not depend on the Bell tests, but really there is no other known way to test for entanglement of separated particles and, as you know, there has been no loophole-free experiment. Not only that but it is possible to find perfectly straightforward local causal explanations for all experiment to date if you take account of the actual variant of Bell test used and actual conditions.

You statement (3) is misleading. The kind of revision of theory that will be needed if entanglement turns out to be not a fact is a fundamental one. It may not involve many changes in the equations that are used, but it involves a huge change in outlook. It would mark the beginning of a new era (or is it a return to an old one?) in which magic (i.e. anything not due to local realist causes) was banished from science.

Caroline

 

[Eye_in_the_Sky]

"non-reality" vs. "nonlocality"

I still do not quite see it. I am unable to convince myself that it is wrong to say "quantum correlations imply nonlocality". I acknowledge that Bell's argument as he originally presented it is not enough to establish that claim, and moreover, that my original argument way back at post #59 is inadequate in this regard. However, if I shift the terms of that argument ever so slightly, my 2) becomes:

2') hidden variables "exist" → nonlocality .

And that is fine.

What then would my 1) become? It would become:

1') hidden variables do not "exist" → state-vector description is "complete" → state-vector description gives a full account of the "real factual situation" → under appropriate conditions, the "real factual situation" in one place will change on account of an action performed at another place arbitrarily far away → nonlocality .

I suppose that the main problem with my 1') has to do with this construct of a "real factual situation". Perhaps it is not necessarily a valid one. Is that so? If we (tentatively) grant validity to that construct, can 1') be invalidated on other grounds?

 

[caribou]

OK, so that was Omnes opinion and you are happy to go along with it. You may not be surprised to know that I do not and that I have my own ideas as to why stones are hard and how a laser works.

I think you'll find it's the opinion of Omnes and most physicists who either founded or developed quantum theory.

 

[Caroline Thompson]

I think you'll find it's the opinion of Omnes and most physicists who either founded or developed quantum theory.

Well yes, the majority of physicists may well believe that without QT we could not explain the hardness of stone of how a laser works. Clearly those who developed the theory fondly hoped that they had now explained everything (and that despite, incidentally, the fact that Bohr and Von Neumann did not think lasers possible until one had been demonstrated to them! See http://freespace.virgin.net/ch.thompson1/People/CarverMead.htm)

Several of the Founding Fathers, though, recognised later in life that they could have been wrong -- that better theories might be possible. And I rather like this quotation:

The scientific community ... is like a pack of hounds ... where the louder-voiced bring many to follow them nearly as often on a wrong path as a right one, where the entire pack even has been known to move off bodily on a false scent.
Samuel Pierpont Langley, 1889​

I first encountered it in the report on one of the Solvay lectures from the 1920's, though I have not been able to trace the exact reference. It was one of the older generation of physicists who said it.

Caroline

 

[DrChinese]

Well yes, the majority of physicists may well believe that without QT we could not explain the hardness of stone of how a laser works. Clearly those who developed the theory fondly hoped that they had now explained everything (and that despite, incidentally, the fact that Bohr and Von Neumann did not think lasers possible until one had been demonstrated to them!

Your point that even famous scientists change their minds as new information becomes available has been discussed ad nauseum in the past. It is well recognized that current theory will be adjusted in the future as we learn more. So what? You use that to justify your own otherwise meritless position by trying to convince us that "maybe" you will turn out to be right in the end. Well, maybe pigs will fly tomorrow as well. In the meantime, I am waiting for you to produce something more than an elaborate conspiracy to hide the "truth" according to Caroline.

Science is about creating useful theory. QM is useful. What you are espousing is essentially that no one can ever know anything - because no level of proof is sufficient for you. Your viewpoint lacks utility.

 

[caribou]

Quantum theory is the most successful physical theory of all and entanglement is a very important part of it. Many people may not understand the true meaning of the superposition of states of distant particles in entanglement but that is very much their problem and not the theory's.

 

[Caroline Thompson]

Your point that even famous scientists change their minds as new information becomes available has been discussed ad nauseum in the past. It is well recognized that current theory will be adjusted in the future as we learn more. So what? You use that to justify your own otherwise meritless position by trying to convince us that "maybe" you will turn out to be right in the end. Well, maybe pigs will fly tomorrow as well.

I'm not talking about pigs flying, DrChinese, but about common sense. It has been out of fashion ever since Einstein's 1905 relativity paper (well actually rather later than that: since he rose to fame after the 1919 eclipse data was claimed to support his GR theory) to believe that we can hope to use our intuition to arrive at valid models of the real world. All I am saying is that the actual data in no case forces this fashion on us. The reason we accept counterintuitive theories is that the mathematics behind them is manageable. They enable us to build formulae that appear to work.

The Bell tests, though, could be shown to be the exception if only a wider range of parameters were used in each experiment. The published results suport QM, but what about other unpublished ones or results that would have been obtained under slightly different conditions? For these conditions, the mathematics of QM becomes intractable. Nobody even attempts it unless it is absolutely forced upon them, and when this happens the services of an expert are required. With my "local realist" models, on the other hand, once you understand the basics of how each piece of apparatus works, anyone can see how the model should be modified. The realist model would, in the hands of someone knowledgeable about the actual apparatus, be more flexible and have greater predictive power than QM

In the meantime, I am waiting for you to produce something more than an elaborate conspiracy to hide the "truth" according to Caroline.

I am not talking of conspiracy, merely of ignorance, together with the consequences of living with a theory to which you cannot apply your intuition. It can lead to absurdities and you have no way of judging when this has happened. It happens, I maintain, in just about every "quantum optics" experiment, not just in the Bell tests. They can all benefit by switching to a realist model.

Science is about creating useful theory. QM is useful.

QM in general may be useful. Quantum optics (the area that includes the Bell test experiments) is redundant. The whole area is already covered by what is essentially classical optics, with just a few extensions to cover things that were not known 100 years ago.

What you are espousing is essentially that no one can ever know anything - because no level of proof is sufficient for you. Your viewpoint lacks utility.

I trust you have read sufficient of my work to know what you are talking about here. I am not talking in general, only about a certain area of physics in which previously accepted standards of scientific explanation have been abandoned on insufficient evidence.

Though I am more concerned with understanding than with utility, in the long term I maintain that applications of "entanglement" will benefit from recognition of the fact that this it not any magical quantum-theoretical phenomenon but merely a result of ordinary correlations of ordinary variables such as polarisation direction. The act of looking at "coincidences" produces results that look strange until you stop to work out (as I did in my Chaotic Ball model) what is really happening. Surely it is unwise to just look at them and say "How strange!" and not investigate further?

Sorry to gabble on, but if it's just my voice against the masses I feel it to be necessary.

Caroline
http://freespace.virgin.net/ch.thompson1/

 

[reilly]

Caroline Thompson writes:I'm not talking about pigs flying, DrChinese, but about common sense. It has been out of fashion ever since Einstein's 1905 relativity paper (well actually rather later than that: since he rose to fame after the 1919 eclipse data was claimed to support his GR theory) to believe that we can hope to use our intuition to arrive at valid models of the real world. All I am saying is that the actual data in no case forces this fashion on us. The reason we accept counterintuitive theories is that the mathematics behind them is manageable. They enable us to build formulae that appear to work.

****
With what time i have for this forum, I should be doing my due diligence on Dr. Chinese's ideas on negative probabilities. But, where do you ever get the idea that common sense and intuition no longer play a role in physics? (If you don't use these, what can you do?)


Very few, if any professional physicisits would agree. Rather, many could cite many occasions in their careers in which common sense/and intuition played a huge role. And, the literature is full of such examples. Your notion that we accept what you term "counterintuitive theories: because of mathematical nicities is, with all due respect, quite wrong. Einstein, Bohr were highly intuitive thinkers, Cooper's approach to explaining superconductivity was highly intuitive -- which, in fact, allowed him, to simplify the math of an interacting electron gas in an appropriate lattice. The WKB approximation is highly intuitive, the Fermi-Thomas approach to heavy atoms is again highly inuitive. Much of basic nuclear physics, thermal neutron sattering for example -- giving the idea of a scattering length, a very useful "intuitive" tool.

There's much more to say, but I've not the time now. I'll say that the history and literature of 20th century physics does not support your contention.

Regards, Reilly Atkinson

 

[Hans de Vries]

Quantum theory is the most successful physical theory of all and entanglement is a very important part of it. Many people may not understand the true meaning of the superposition of states of distant particles in entanglement but that is very much their problem and not the theory's.

There are no non-local "action on a distance" terms in the Standard Model
which describes the Electro Magnetic, Weak and Strong Interactions.
It is a local Quantum Field Theory.

Non-local theories are in serious conflict with both Special Relativity
and Quantum Mechanics.

Non-local theorist claim that instantaneous action on a distance doesn't
violate Special Relativity with arguments that seem more like a word play.

Quantum teleportation is supposed to work because it "Circumvents"
Heisenberg's uncertainty principle according to Zeilinger.

Regards, Hans

 

[Caroline Thompson]

... where do you ever get the idea that common sense and intuition no longer play a role in physics? (If you don't use these, what can you do?)

Perhaps I did not choose my wording sufficiently carefully. What I said was "It has been out of fashion [recently] to believe that we can hope to use our intuition to arrive at valid models of the real world."

What I meant was simply that it has become acceptable to use models that are not intuitive when this seems to be necessary. This may not matter in some contexts, but if the idea is extended to mean that no intuitive model is ever going to be possible we need to think again. Have we been sufficiently careful in deciding whether or not the observed facts really do imply this?

I maintain that Dirac et al's mathematics forced the idea of entanglement of separated particles on us and our reluctance to relax the assumption of the particle nature of light has blinded us to alternative, purely intuitive, explanations of the observations.

Einstein set the scene for this in two ways:

a) by inventing the "photon" (though this was not consistently used as meaning an indivisible particle: at one stage he referred to it as "needle radiation", which has no such implications) and
(b) by postulating the constancy of the speed of light, declaring the notion of an underlying wave medium -- the aether -- to be superflous.​

Heisenberg, when he first introduced his Uncertainty Principle, actually referred to Einstein's counterintuitive idea of the constancy of the speed of light as a precedent. See page P117 of:

Hendry, John, “The Creation of Quantum Mechanics and the Bohr-Pauli Dialogue”, D Reidel Publishing Company 1984​

... Your notion that we accept what you term "counterintuitive theories: because of mathematical nicities is, with all due respect, quite wrong. Einstein, Bohr were highly intuitive thinkers, Cooper's approach to explaining superconductivity was highly intuitive -- which, in fact, allowed him, to simplify the math of an interacting electron gas in an appropriate lattice. The WKB approximation is highly intuitive, the Fermi-Thomas approach to heavy atoms is again highly inuitive. Much of basic nuclear physics, thermal neutron sattering for example -- giving the idea of a scattering length, a very useful "intuitive" tool.

There's much more to say, but I've not the time now. I'll say that the history and literature of 20th century physics does not support your contention.

Right, so the initial maths tends to be based on intuition and experience, but what happens next is what concerns me. The maths gets extrapolated. It is assumed to apply in situations broader than its original purpose. Perhaps I should not generalise, but this is what has, I maintain, happen in the case of quantum entanglement. It was an unwanted side effect of trying to apply mathematics intended for single particles to pairs of them. A decision was taken to assume that these could be modeled by one, "nonseparable", wave function. This assumption led to a nice neat formula, one of whose consequences was that Malus' Law would apply to coincidence counts between two separate polarisers just as it was (so long as you assume detection rates proportional to input intensities) known to apply to the output from crossed polarisers placed "in series".

But this extrapolation was not based on any physical model and is, under local realist theories, false. Experiments only approximately back it up, and only in a limited set of conditions, sometimes only after data adjustments that themselves rely for their justification on further quantum-theoretical mathematics. [See Thompson. C H: “Subtraction of ``accidentals'' and the validity of Bell tests”, Galilean Electrodynamics 14 (3), 43-50 (May 2003).
http://arXiv.org/abs/quant-ph/9903066]

Incidentally, if I am right then there is no need to delve into the question of negative probabilities. These have never been shown to happen, which is scarcely surprising since the concept is mathematically impossible.

Caroline
http://freespace.virgin.net/ch.thompson1/

 

[vanesch]

Quantum optics (the area that includes the Bell test experiments) is redundant. The whole area is already covered by what is essentially classical optics, with just a few extensions to cover things that were not known 100 years ago.

I defy you to explain the results of:

Am. J. Phys. Vol 72, No 9, September 2004

with classical optics.

cheers,
Patrick.

 

[caribou]

There are no non-local "action on a distance" terms in the Standard Model
which describes the Electro Magnetic, Weak and Strong Interactions.
It is a local Quantum Field Theory.

Non-local theories are in serious conflict with both Special Relativity
and Quantum Mechanics.

Non-local theorist claim that instantaneous action on a distance doesn't
violate Special Relativity with arguments that seem more like a word play.

Quantum teleportation is supposed to work because it "Circumvents"
Heisenberg's uncertainty principle according to Zeilinger.

Regards, Hans

Actually, the "true meaning" I was referring to is that apparently people have been mistaken when they think there are "spooky action-at-a-distance" and faster-than-light effects in quantum theory.

If I understand experts like Zurek and Omnes, things like the EPR experiment apparently involve a superposition of measurement outcomes and no faster-than-light effects.

 

[Hans de Vries]

If I understand experts like Zurek and Omnes, things like the EPR experiment apparently involve a superposition of measurement outcomes and no faster-than-light effects.

There is definitely faster then light correlation in the teleporting theories.

The twisted argument is that it doesn't count because it can not
be checked immediately if an event is correlated to another distant
one. The check would have to go with the speed of light.

With some real bad luck I could get killed instantaneously by some
astronomical catastrophe some 100 lightyears away via entanglement.
It would however take 100 years to check that my dead was correlated
to the distant catastrophe.

So, am I not dead then as long as the correlation is not checked?
Doesn't it count?

Regards, Hans

 

[vanesch]

If I understand experts like Zurek and Omnes, things like the EPR experiment apparently involve a superposition of measurement outcomes and no faster-than-light effects.

Yes ! That's also what's my opinion. It is the observer who considers the correlation that does "the collapse thing", and not the two distant "observers" who just entangle their message with the part of the state of the received subsystem.
(but the price to pay for that opinion is a kind of solipsism...)

 

[alexepascual]

Caroline:
To make new thread, while looking at the posts on this thread, look at the top of the page. There should be a box that says:
Physics > Quantum Physics > How do particles become entangled ?
Click on "Quantum Physics", which will take you to the list of threads under this topic.
On the top left of that screen, just above the first thread, you'll see a button that says: "New Thread". Good luck!

Eye_in_the_sky:
Things came up and I am still reading your post. Some of it I understand, some of it I have questions. But I'll read it again and do a little more thinking before I respond.

 

[Caroline Thompson]

Yes ! That's also what's my opinion. It is the observer who considers the correlation that does "the collapse thing", and not the two distant "observers" who just entangle their message with the part of the state of the received subsystem.
(but the price to pay for that opinion is a kind of solipsism...)

Never mind the interpretation! What Bell showed was (as EPR had suspected), that the QM theory of entangled particles involves something in conflict with local realism. It is this that bothers me -- the failure of basic assumptions such as the ablity to predict probabilities of joint outcomes of independent events by multiplying the individual probabilities.

Before some people jump on me and say that the two sides are not independent, do look at the actual local realist calculation given in Appendix C of http://arXiv.org/abs/quant-ph/9903066! You will see then just what role the hidden variable, lambda, plays and at what stage the multiplication takes place. It is before integration over lambda.

Bell discusses the necessary assumptions in pp 36-37 of

Bell, John S, The Speakable and Unspeakable in Quantum Mechanics, Cambridge University Press 1987​

Caroline

 

[vanesch]

Never mind the interpretation! What Bell showed was (as EPR had suspected), that the QM theory of entangled particles involves something in conflict with local realism.

That's true if you think that the result of a measurement is classical and "graved in stone". However, if you consider that the "measurement" just transmits the entanglement, and that the result also comes in a superposed state, you just get, when you look at the correlations of the results from both distant photodetectors, a local interference of entangled systems. So this saves the "local" part. I'm not sure it saves the "realist" part :tongue2:
Imagine sending out Bob to the left photodetector, and Alice to the right photodetector. They come back in a superposed state, with all different possible results in a superposition, and it is when you look at both of them that the actual von Neuman measurement takes place, for you, as an observer. It's all in the mind

But ok, if you don't buy into photons, you won't buy into this. Although it is 100% in agreement with all of existing physics