EPR Debate: Nature Agrees with Einstein

[ZapperZ]

I think it is in http://arxiv.org/abs/quant-ph/0102139 that Lev Vaidman explains why, though an inequality was violated, we don't have to interpret it as illustrating entanglement: the ions in Rowe's experiment were very close together. The measurements on them could not be considered (as required for the Bell inequality) to be independent.

Cat

While this may not be entirely relevant to the point you're trying to make, take note that the existence of entanglement is not solely verified via the EPR-type experiments. 2 entangled photons, for example, are not separable and can essentially be described as a connected, single system. It means that it is a macro particle with twice the energy of a single, isolated photon. If this is true, then one should be able to do a diffraction experiment with a higher resolution using the entangled pair than with single photon since the entangled macro particle has twice the energy (and thus, half the wavelength) of a single, unentangled photon.

Guess what? That's what has been observed, and in two separate experiments![1,2] The entangled photons can beat the diffraction limits of single photons. The first experiment showed interference patterns from a state of 3 entangled photons, while the other showed a state of 4 entangled photons. In both cases, the resolution was better than for a single photon: they were lambda/3 and lambda/4 respectively, as expected.

One can read a brief report of these experiements here

http://physicsweb.org/article/news/8/5/6

As is typical in physics, a particular idea, principle, or theory, isn't verified with just one experiment. Often, several difference experiments and techniques are required for a convincing verification. This appears to be the case here.

Zz.

[1] P. Walther et al., Nature v.429, p.158 (2004).
[2] M.W. Mitchell et al., Nature v.429, p.161 (2004).

 

[marlon]

One can read a brief report of these experiements here

http://physicsweb.org/article/news/8/5/6

As is typical in physics, a particular idea, principle, or theory, isn't verified with just one experiment. Often, several difference experiments and techniques are required for a convincing verification. This appears to be the case here.

Zz.

[1] P. Walther et al., Nature v.429, p.158 (2004).
[2] M.W. Mitchell et al., Nature v.429, p.161 (2004).

Hi ZapperZ,

this article is very interesting. I do have a question though because this experiment is not entirely clear to me. Let me explain how i see it : if two photons are entangeled their wavelength is indeed half the size of one photon. These photons can be entangeled via parametric down conversion. In order to check whether photons are entangeled can you do this ? : Suppose you construct a plate through which the photons have to pass. Make little holes in this plate so that photons can pass through them. Now (according to me, but i am not sure) the clue is to make the dimension of these holes as big as the wavelength of an entangeled pair so that "ordinary" unentangeled photons cannot pass through (their wavelength is too big)

Hence, the photons you detect after passing through the plate are entagneled for sure.

Is this the way to look at this experiment and does my point make sense?

Please elaborate if i am wrong...

Thanks in advance.

regards
marlon

 

[Cat]

Lev doesn't think that experiment has eliminated the detection ("fair sampling") issue because of the locality issue. But that is merely one person's opinion.

Surely one experiment with perfect detectors has no effect on the logic of a loophole that is present when they are not perfect? [See the original paper on the subject of the detection loophole -- Pearle, P, “Hidden-Variable Example Based upon Data Rejection”, Physical Review D, 2, 1418-25 (1970)]

It is clear to me from the Rowe and Aspect experiments (and others such as Weihs):

a. Locality: the Inequality is violated whether or not the apparatus is space-like separated, per Weihs. (Requiring this never made any sense in the first place, because it requires the existence of physical effects never otherwise witnessed.)

I agree that, in general, the separation is irrelevant. However see below for more on the Rowe et al experiment.

b. Fair Sampling: the Inequality is violated whether or not a fair sample is obtained, per Rowe. (Requiring a complete sample never made sense to me either, as a large subsample should not possibly show more correlations than are actually present in the full population.)

No, this has not been proven and the logic of Pearle's paper says it is not in general true. I've had a look at one of the papers on Rowe's experiment, and it is open to more problems than have so far been discussed. It is not only a straightforward matter of whether or not signals could have been exchanged (the locality loophole) and whether or not the sample was fair (the detection loophole). We agree, it seems, that the first is open but irrelevant, the second closed (since the sample was almost the entire population).

The problem here seems to be that Bell's inequality depends on being able to set your detectors independently and also on being able to measure your particles separately. It is not at all clear that the detector settings can be regarded as independent, and it is most certainly not true that the particles are measured separately. What is measured is the intensity of the combined signal from both. There is no way, when this is at half strength, of knowing which particle contibuted that half -- See Kielpinski, David et al, “Recent Results in Trapped-Ion Quantum Computing”, http://arxiv.org/abs/quant-ph/0102086.

Cat

 

[marlon]

Anybody here whot can help me out with the question in my previous post on detecting entangeled photons ?

Thanks
marlon

 

[ZapperZ]

Hi ZapperZ,

this article is very interesting. I do have a question though because this experiment is not entirely clear to me. Let me explain how i see it : if two photons are entangeled their wavelength is indeed half the size of one photon. These photons can be entangeled via parametric down conversion. In order to check whether photons are entangeled can you do this ? : Suppose you construct a plate through which the photons have to pass. Make little holes in this plate so that photons can pass through them. Now (according to me, but i am not sure) the clue is to make the dimension of these holes as big as the wavelength of an entangeled pair so that "ordinary" unentangeled photons cannot pass through (their wavelength is too big)

Hence, the photons you detect after passing through the plate are entagneled for sure.

Is this the way to look at this experiment and does my point make sense?

Please elaborate if i am wrong...

Thanks in advance.

regards
marlon

Keep in mind that to get any effects from diffraction, you need a opening that is of the order of, or less than the size of the wavelength. If the opening is considerably larger than the wavelength, you get no diffraction effects.

What you get in this case is that to get a diffraction pattern with the 2-photon case, the opening must be smaller than what you get with the 1-photon case. This is because the wavelength of the 2-photon macro particle is smaller than the single photon. So this is in the opposite direction of what you are describing.

Zz.

 

[marlon]

Keep in mind that to get any effects from diffraction, you need a opening that is of the order of, or less than the size of the wavelength. If the opening is considerably larger than the wavelength, you get no diffraction effects.

What you get in this case is that to get a diffraction pattern with the 2-photon case, the opening must be smaller than what you get with the 1-photon case. This is because the wavelength of the 2-photon macro particle is smaller than the single photon. So this is in the opposite direction of what you are describing.

Zz.

Yes, thanks a lot Zz, i got the picture now. Indeed what i stated previously is the exact opposite of what is going on. I realize that now.


regards
marlon

 

[Hans de Vries]

Hi ZapperZ,

this article is very interesting. I do have a question though because this experiment is not entirely clear to me. Let me explain how i see it : if two photons are entangeled their wavelength is indeed half the size of one photon. These photons can be entangeled via parametric down conversion. In order to check whether photons are entangeled can you do this ? :

This article certainly didn't go unnoticed. I remember reading it when
it came out. I haven't seen any further details yet unfortunately.

The cost of the lens optics in semiconductor lithography waver processing
equipment goes up from $3 million to 6$ million if the laser wavelength is
reduced from 193 nm to 153 nm.

So you can imagine that any help in breaking the diffraction limit is really
appreciated! There is already a big bag of tricks used to break this limit.
Optical Proximity Correction, Phase Shift Masks and Liquid Immersion will
make it possible to draw 32 nm wide lines with 193 nm laser light in
production systems at the end of the decade.

Suppose you construct a plate through which the photons have to pass. Make little holes in this plate so that photons can pass through them. Now (according to me, but i am not sure) the clue is to make the dimension of these holes as big as the wavelength of an entangeled pair so that "ordinary" unentangeled photons cannot pass through (their wavelength is too big)

Hence, the photons you detect after passing through the plate are entagneled for sure.

It has been shown that light can pass through holes which are much
smaller than its wave length. Presumably by interacting with the electrons
in the material of the plate.

What about simple color filters?


Regards, Hans

 

[RandallB]

an x-polarized photon can just as well be seen as a superposition of a 45 degree left, and a 45 degree right polarized photon. And then only one of the two components gets true"through".

The term "x-polarized" dosn't mean "any" polarized photon does it? and would not include a V "|" or a H "-" photon would it?
Superposition of a V & H would be "+"
And if using a non perpendicular converter (call it type I) would the superposition types be discribed as "||", "//", "\\", "--"?

However, in this particular case, the analogy with classical optics is striking: you wouldn't argue that something "tilted" the plane of the E-field when it went through a polarizer, right ? Well, exactly the same thing applies to the photon.
Patrick.

Based on the fact that light goes through a set of H D V filters don't we have to argue that something somehow does tilt or turn and change the polarization angle??
Randall B

 

[DrChinese]

Can an experimental test of entanglement ever be considered complete?

The problem here seems to be that Bell's inequality depends on being able to set your detectors independently and also on being able to measure your particles separately. It is not at all clear that the detector settings can be regarded as independent, and it is most certainly not true that the particles are measured separately.[/url].

Cat

I do not agree with this statement, and I don't think it is represented in Bell's Theorem. I realize that locality is represented in the Theorem, I am not questioning that.

1. Suppose we set the polarizers at 22.5 degrees for one hour, and measure many event correlations. I am not concerned that the polarizer at A sent a message to the polarizer at B. I believe this is a red herring that confuses the locality issue. The observed correlation will be .8536 (ideal case of course) and we can be happy with that value as being valid in agreement with the predictions of the QM formalism. What underlying mechanism accomplishes this is totally irrelevant to this experimental result, just as the mechanism of the double slit is not relevant to that result. In each case, the Heisenberg Uncertainty Principle is respected. That's QM!

2. If (during its measurement) the particle at A sends a message to the particle at B via a non-local communication channel which is invisible to us, then that could explain the observed results (non-local realistic). This is true whether the measuring apparatus is space-like separated or not! This is where the assumption of locality fits into the Theorem. In other words: if you are postulating a non-local theory containing hidden variables, then Bell's Theorem does not apply at all.

3. On the other hand, the mathematical formalism of Bell's Theorem incorporates an explicit requirement for realistic (hidden variable) theories to which 2. does not apply - i.e. local realistic theories only. That requirement is the existence of a C to go along with polarizer angle settings A and B, the hypothetical other measurement that could have been performed. This leads to bounds on values that any such LR (LHV) theory can yield. And this has absolutely nothing to do with the measuring apparatus settings at A and B. It's all about throwing C into the equation. If there is no C, it's not realistic in the first place!

Bell's Theorem essentially says that the eight permutations below add to a total probabilty of 1:

[1] A+ B+ C+ (and the likelihood of this is >=0)
[2] A+ B+ C- (and the likelihood of this is >=0)
[3] A+ B- C+ (and the likelihood of this is >=0)
[4] A+ B- C- (and the likelihood of this is >=0)
[5] A- B+ C+ (and the likelihood of this is >=0)
[6] A- B+ C- (and the likelihood of this is >=0)
[7] A- B- C+ (and the likelihood of this is >=0)
[8] A- B- C- (and the likelihood of this is >=0)

...But that there are no such predictive values for A, B, C that match QM's predictions. You don't need to do an experiment to reach this conclusion. Without moving from my armchair, I can see that all LR theories respecting Bell make radically different predictions than QM. Therefore experiments that support QM also rule out LR.

After all, the purported local counter-explanations are essentially "un-realistic" in the first place; we are told to expect MORE correlations than unentangled random chance should allow! It is the reverse that should happen.

4. It makes no sense to say that the experiment was contaminated so that entanglement "appears to occur" even though there is no actual entanglement. That isn't really science. If it is there, where is it? What causes it? Measure it! Explain it! Why haven't we ever noticed it before? Why doesn't it show up in experiments designed to look for it? Test results don't vary when heretofor unknown local causes are eliminated as a factor, and they don't vary when sampling is eliminated as a factor. If these were really loopholes, tests would have identified this. But instead, every Bell test shows the same results, LR is ruled out by 5/10/20/30+ standard deviations.

Perhaps someone should write a paper entitled "Can an experimental test of entanglement ever be considered complete?"

 

[DrChinese]

Surely one experiment with perfect detectors has no effect on the logic of a loophole that is present when they are not perfect? [See the original paper on the subject of the detection loophole -- Pearle, P, “Hidden-Variable Example Based upon Data Rejection”, Physical Review D, 2, 1418-25 (1970)]

Cat

I don't think I follow your reasoning, assuming I have it correct. You are saying that the loophole is a loophole even if it is determined not to be a loophole?

Suppose you postulate that there is a variable that affects the results of an experiment. Then you measure that variable, and find that its contribution to the experimental result is zero. The conclusion, pure and simple, is that your postulated "loophole" is non-existent. Therefore it is no longer a loophole. Period.

Example: I hypothesize that experiments performed on Tuesday yield more correlations than those performed on Wednesday. Simply run the test on both days and now you know the answer - no effect. You don't need to run all subsequent tests on both Tuesday and Wednesday to know they are valid.

How could it ever be otherwise? (Unless of course, you simply reject the experiment in toto.)

 

[Cat]

I don't think I follow your reasoning, assuming I have it correct. You are saying that the loophole is a loophole even if it is determined not to be a loophole?

Sorry, you're right: what I wrote was not logical. What I meant made sense but only because, as you suspected, I reject the Rowe et al experiment in toto. I maintain that none of the experiments to date have shown violations of a Bell inequality except in the presence of "real", functional, loopholes.

Cat

 

[RandallB]

...there are no such predictive values for A, B, C that match QM's predictions.

That's only true when the predictions are based on Light wave theory.
I don't think Dr E. Dr P. or Dr R had a problem with looking at light as a particle. Nether did Newton actually, but that was long before these issues. They just had a problem with the FTL implications of QM. AND suspected, hoped, believed, that a more complete description might help resolve how much FTL activity is real, if any.
Where “C” & LR is helpful in confirming that Wave Theory is incomplete and that light must be Quantized. I don't see where it's helpful in resolving the EPR issue.

HOWEVER I do find the implications of the A-B test very interesting as I believe I've made an incorrect assumption there! I'd like to take a closer look at the 100% correlation expected by QM and reported by the testing, Shouldn't the expected correlation be 75%??

Just to review the test, The entangled generator is producing photon pairs with polarization separated by a fix unchanging angle 0 or 90 depending on 'type'. But the base original angle for each set of pairs is random though 360 degrees. Therefore testers A and B can be rotated together to any measuring angle and the same result in rate & number of hits and the same 100% correlation is always found. ---Correct?-

Source of 75% & 100% correlation conflict-- a cross check of the test :
If we replace the "entangled" light source with TWO independent light sources that only generate photons with a fixed polarization, wired to generate simultaneous light signals, polarized and aligned to match the original 0 or 90 degree separation type as needed. But to duplicate the random base alignment of each photon pair, like the original entangled source generates, their base angle is incrementally advanced around 360 degrees for equal time intervals of the total test.
Under these conditions A and B will always see the light pass in V alignment and always blocked in the H alignment,100% correlation. But when the alignment is on the diagonal 50% of the signals will go through, and only a 50% chance of correlation.
The end result is total testing will give 75 % correlation.
Has a test run like this been done? Seems pretty simple I'd hope someone has.
IS there any doubt this is true?

YET, Testing with the entangled source shows 100% correlation!
Isn't this more significant than the arguing over loopholes? How does the correlation on the diagonals get to 100%?
(Some FTL function insures common interaction with off baseline angled filters?)
OR (maybe a better description should be possible as Mr. E P R argued?)
Has any attention been given this? - I.E. has anyone even tried to propose a non-QM explanation?
Does QM provide any explanation? Or is having a statistical form that correctly predicts the results all that can be expected of QM?

 

[DrChinese]

Originally Posted by DrChinese: ...there are no such predictive values for A, B, C that match QM's predictions.

1. That's only true when the predictions are based on Light wave theory.

2. HOWEVER I do find the implications of the A-B test very interesting as I believe I've made an incorrect assumption there! I'd like to take a closer look at the 100% correlation expected by QM and reported by the testing, Shouldn't the expected correlation be 75%??

Just to review the test, The entangled generator is producing photon pairs with polarization separated by a fix unchanging angle 0 or 90 depending on 'type'. But the base original angle for each set of pairs is random though 360 degrees. Therefore testers A and B can be rotated together to any measuring angle and the same result in rate & number of hits and the same 100% correlation is always found. ---Correct?-

3. Source of 75% & 100% correlation conflict-- a cross check of the test :
If we replace the "entangled" light source with TWO independent light sources that only generate photons with a fixed polarization, wired to generate simultaneous light signals, polarized and aligned to match the original 0 or 90 degree separation type as needed. But to duplicate the random base alignment of each photon pair, like the original entangled source generates, their base angle is incrementally advanced around 360 degrees for equal time intervals of the total test.
Under these conditions A and B will always see the light pass in V alignment and always blocked in the H alignment,100% correlation. But when the alignment is on the diagonal 50% of the signals will go through, and only a 50% chance of correlation.
The end result is total testing will give 75 % correlation.
Has a test run like this been done? Seems pretty simple I'd hope someone has.
IS there any doubt this is true?

YET, Testing with the entangled source shows 100% correlation!
Isn't this more significant than the arguing over loopholes? How does the correlation on the diagonals get to 100%?
(Some FTL function insures common interaction with off baseline angled filters?)
OR (maybe a better description should be possible as Mr. E P R argued?)
Has any attention been given this? - I.E. has anyone even tried to propose a non-QM explanation?
Does QM provide any explanation? Or is having a statistical form that correctly predicts the results all that can be expected of QM?

1. QM makes specific predictions in this case. You cannot devise a theory in which A, B and C have independent simultaneous reality and match QM.

2. Yes 100% is the QM prediction for 0 degrees. But there is no such thing as the "the base original angle for each set of pairs is random though 360 degrees" as you state. This is a classical picture and is inconsistent with observation.

3. Your example, assuming I understand it, would yield 75% instead of 100% as predicted by QM. Therefore, I would conclude that your example is not representative of what is actually happening - although it would respect Bell's Inequality.

 

[RandallB]

2. But there is no such thing as the "the base original angle for each set of pairs is random though 360 degrees" as you state. This is a classical picture and is inconsistent with observation.

What are you talking about "classical" here??
I'm referring to the entangled photon generator!

OR are you saying that a, parametric down converters, that generates perpendicularly polarized photon pairs (Type II) gives polarizations of 0 degrees and 90 degrees only!
With the twins never being at the same angle, (Type I, always the same) BUT always at ether 0 or 90 degrees and never any other angle?
Thus the test in A must set 0 to 0 degrees and B must set 0 to 90 degrees (Type II) for the test to work. Because if they were set to say -45 and +45 a test run still have light coming through half the time but it would only have & QM would predict a 50% correlation??
Thus one of the critical settings is aligning the observer’s polarization to the alignment of the down converter that produces the entangled photons??

If so I had miss-understood the test configuration, and the need to aline the test to the down converter, which bothers me a bit.
DO I have the above correct??

RB
(Also do you know if I have Type I and Type II defined correctly)

 

[DrChinese]

What are you talking about "classical" here??
I'm referring to the entangled photon generator!

You said "random through 360 degrees" and there is nothing random through 360 degrees. The light is polarized upon going through the prisms, not before.

I am fine with what you describe otherwise.

 

[RandallB]

You said "random through 360 degrees" and there is nothing random through 360 degrees. The light is polarized upon going through the prisms, not before.

I am fine with what you describe otherwise.

I'n never understood that the source light was polarized in fixed positions before. I thought they could come out of the parametric down converter at any angle - just that they had to a fixed angle 0 or 90 from each other.

I think that they are always fixed at 0 or 90 degrees in relation to outside observers, well I think that's a problem for me. I'll need to think on it a bit.

RB

 

[DrChinese]

I'n never understood that the source light was polarized in fixed positions before. I thought they could come out of the parametric down converter at any angle - just that they had to a fixed angle 0 or 90 from each other.

I think that they are always fixed at 0 or 90 degrees in relation to outside observers, well I think that's a problem for me. I'll need to think on it a bit.

RB

You have it fine... all I mean is that it is "unpolarized" before it is polarized. The point I am making by saying it is unpolarized is that the polarization is neither known nor definite.

 

[RandallB]

You have it fine... all I mean is that it is . The point I am making by saying it is unpolarized is that the polarization is neither known nor definite.

"unpolarized" before it is polarized by the parametric down converter. Correct.

In our experiments the photon that is coming to the test area is known to be polarised. And that it must be polerized in either a H or V direction based on how parametric down converters work. Never at any other angle. It only the "either or" part that not known. The two angles they can come in at H and V or 0 and 90 degrees is known in advance.

Just want to be sure I have this right, becuse it is not what I'd thought before.

 

[DrChinese]

"unpolarized" before it is polarized by the parametric down converter. Correct.

In our experiments the photon that is coming to the test area is known to be polarised. And that it must be polerized in either a H or V direction based on how parametric down converters work. Never at any other angle. It only the "either or" part that not known. The two angles they can come in at H and V or 0 and 90 degrees is known in advance.

Just want to be sure I have this right, becuse it is not what I'd thought before.

No, PDC type I produces pairs that are linearly polarized but the only thing we know is that they are parallel. Type II produces perpendicular pairs.

Here is a spot that discusses a bit: http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/entangle.html

If the actual polarization was known, the spin correlation would cease.

 

[RandallB]

No, .

No to what?
The link you provided seems to confirm what I said - That is both
PDC type I and type II produces polarizations that are V or H. Photon pairs might be 1) VV or HH OR 2) VH or HV ; depending on type. But as I said never at any other angle other than 0 or 90 (like a 15 & 15 for a type I).

BTW Thanks for confirming I understood correctly in calling Type II as the one making perpendicular pairs.

Maybe you miss-understood what I'd said?

If the actual polarization was known, the spin correlation would cease.

Well sure, TESTER "knows" the photon will be 'either' H 'or' V but it is unknown what it could be till it is tested. More than unknown, from a QM view it is "Undetermined".

 

[Hans de Vries]

The link you provided seems to confirm what I said - That is both
PDC type I and type II produces polarizations that are V or H. Photon pairs might be 1) VV or HH OR 2) VH or HV ; depending on type. But as I said never at any other angle other than 0 or 90 (like a 15 & 15 for a type I).

This is indeed the case (some of the calculations, including mine, made in
the threads here assumed that the angle was arbitrary... )
The angles are fixed and can only be 0 or 90 degrees. An indication is
also the e^ia value as a result of the birefringent nature of the

\frac{1}{\sqrt{2}} ( |H\rangle_A|V\rangle_B + e^{i\alpha}|V\rangle_A|H\rangle_B )

crystal which causes a different speed for H and V photons. This
value is fixed and is normally corrected with an additional birefringent
phase shifter.


Regards, Hans.

[1] Generation of correlated photon pairs in type-II
--- parametric down conversion – revisited
--- http://scotty.quantum.physik.uni-muenchen.de/publ/achtbild.pdf

[2] Thesis. Jian-Wei Pan (see chapter 2.3)
--- http://www.quantum.univie.ac.at/publications/thesis/jwpdiss.pdf

 

[DrChinese]

No to what?
The link you provided seems to confirm what I said - That is both
PDC type I and type II produces polarizations that are V or H. Photon pairs might be 1) VV or HH OR 2) VH or HV ; depending on type. But as I said never at any other angle other than 0 or 90 (like a 15 & 15 for a type I).

BTW Thanks for confirming I understood correctly in calling Type II as the one making perpendicular pairs.

Maybe you miss-understood what I'd said?

Well sure, TESTER "knows" the photon will be 'either' H 'or' V but it is unknown what it could be till it is tested. More than unknown, from a QM view it is "Undetermined".

There is no such photon state as you describe. A photon cannot be polarized either H or V (unknown and definite) and still be at 0 or 90 degrees. If you don't know, you don't know. Once you do know, you know.

To say it a different way... There is nothing special about 0 and 90 degrees. So there is no angle at which you can set a second set of polarizers and get any different correlation results. You are just as free to call any results as H and V. As always in all EPR tests, it is the angle between the 2 measuring polarizers that controls correlation results and nothing else.

 

[RandallB]

As always in all EPR tests, it is the angle between the 2 measuring polarizers that controls correlation results and nothing else.

This is exactly what I’d said before and you’d corrected me on!
Are you changing your mind or making a point incorrectly?

Based on you statement in BOLD : Starting with “2 measuring polarizers” one at 0 the other at 90 & Type II entangled photons And getting 100% correlation.
Then adjusting the “2 measuring polarizers” to -45 and +45 degrees, without making any other changes, rerunning the test!

I had thought I’d still get 100% correlation with such a rerun test, then you’d corrected me since there is no “Random 360 degree effect”, and now also confirmed Hans as well. The result should now be 50 % correlation.

BUT, now you claim that it is “the angle between the 2 measuring polarizers that controls correlation results and nothing else”!
Since that angle between them has not changed the result should stay at 100% correlation. As the realignment to diagonals or any angle is part of the "nothing else" that doesn’t matter.

So which is it? – your statement above is correct and the photon coming in can be expected to have ANY polarization angle. (Randomly through 360).

OR your above statement is wrong. And the photon coming in can only be expected to have one of two polarization angles 0 or 90 degrees? Thus while maintaining the angle between the 2 measuring polarizers, their alignment will greatly affect the correlation.

 

[DrChinese]

This is exactly what I’d said before and you’d corrected me on!
Are you changing your mind or making a point incorrectly?

Based on you statement in BOLD : Starting with “2 measuring polarizers” one at 0 the other at 90 & Type II entangled photons And getting 100% correlation.
Then adjusting the “2 measuring polarizers” to -45 and +45 degrees, without making any other changes, rerunning the test!

I had thought I’d still get 100% correlation with such a rerun test, then you’d corrected me since there is no “Random 360 degree effect”, and now also confirmed Hans as well. The result should now be 50 % correlation.

BUT, now you claim that it is “the angle between the 2 measuring polarizers that controls correlation results and nothing else”!
Since that angle between them has not changed the result should stay at 100% correlation. As the realignment to diagonals or any angle is part of the "nothing else" that doesn’t matter.

So which is it? – your statement above is correct and the photon coming in can be expected to have ANY polarization angle. (Randomly through 360).

OR your above statement is wrong. And the photon coming in can only be expected to have one of two polarization angles 0 or 90 degrees? Thus while maintaining the angle between the 2 measuring polarizers, their alignment will greatly affect the correlation.

Sorry if my words were not clear. I don't think we are particularly far apart, and I probably have over-emphasized some minor nuances.

You will get the same kind of results as long as the two polarizers are 90 degrees apart. The polarizers can be rotated through 360 degrees and that will still be true. The coincidence rate is 100% (ideal case).

We can talk about H or V relative to a polarizer set at any angle. The only point I intended to make about the 360 degree deal was that the photons themselves do not have polarizations at all in-between angles. It is the polarizers that "control" that element.

 

[RandallB]

2. Yes 100% is the QM prediction for 0 degrees. But there is no such thing as the "the base original angle for each set of pairs is random though 360 degrees" as you state. This is a classical picture and is inconsistent with observation.

From your post 113
So your revising your statement above - When observer A sees a photon pass though, no information is gained as to what the polarization was prior to passing the A's filter. The presenting angle could have been any random (through 360) unknown angle not just H or V.

For example if the photon passes and is detected byA. A only knows what the polarization is after passing. Assuming the result of the initial interaction with the filter was a photon at a 45 degree diagonal with only a 50% chance of passing and it did pass. But having passed, A now knows that the in test area B is a similar diagonal photon with a 50% chance of passing. However A also knows that (regardless of the 50-50 chance of passing in area B) that it will pass or has already passed. Neither A nor B will ever know what that polarization angle on interaction was. Nor will they know, based on that pre-filter angle how remote the chance (lucky) the passing was. Only that they, A and B, will have the same “luck” such that 100% correlation is seen.

And the best theory we have to explain them having the same “luck” is QM entanglement.

 

[DrChinese]

From your post 113
1. So your revising your statement above - When observer A sees a photon pass though, no information is gained as to what the polarization was prior to passing the A's filter. The presenting angle could have been any random (through 360) unknown angle not just H or V.

2. For example if the photon passes and is detected byA. A only knows what the polarization is after passing. Assuming the result of the initial interaction with the filter was a photon at a 45 degree diagonal with only a 50% chance of passing and it did pass. But having passed, A now knows that the in test area B is a similar diagonal photon with a 50% chance of passing. However A also knows that (regardless of the 50-50 chance of passing in area B) that it will pass or has already passed. Neither A nor B will ever know what that polarization angle on interaction was.

3. Nor will they know, based on that pre-filter angle how remote the chance (lucky) the passing was. Only that they, A and B, will have the same “luck” such that 100% correlation is seen.

4. And the best theory we have to explain them having the same “luck” is QM entanglement.

1. Not revising anything, but I am sure it could appear that way. As I said, my words may have fallen short. However, it is the idea that the photons had a definite polarization prior to being measured that I am questioning.

2. Not sure we are saying the same thing, so I will try to describe it:

-PDC type II pair creation. Ideal case.
-Entangled photon a passes through polarizer A set at 45 degrees, witnessed by observer AA.
-Entangled photon b passes through polarizer B set at -45 degrees, witnessed by observer BB.
-AA and BB individually see random patterns of + (hit) and - (misses).
-A 50-50 split of + and - will result.
-When AA sees +, BB also will see +.
-When AA sees -, BB also will see -.
-And vice versa. So there is 100% correlation.

As best as I can tell, we agree on this.

3. Not sure what you mean by "pre-filter" angle. It there is a pre-filter angle (which is subject to philosophical debate), it is limited to 4 possibilities:

Parallel to A.
Perpendicular to A.
Parallel to B.
Perpendicular to B.

These are the only possibilities consistent with experiment and Bell's Theorem. Note that I am not asserting these are actual and real, just that they could be. Nor am I asserting I understand how these 4 angles could be the result from the mechanics of the setup, or in fact that anyone understands this.

4. Yes, QM makes the prediction. It is probabilistic in that sense.

 

[RandallB]

#3. Not sure what you mean by "pre-filter" angle. It there is a pre-filter angle (which is subject to philosophical debate), it is limited to 4 possibilities:

Parallel to A.
Perpendicular to A.
Parallel to B.
Perpendicular to B.

These are the only possibilities consistent with experiment and Bell's Theorem. Note that I am not asserting these are actual and real, just that they could be. Nor am I asserting I understand how these 4 angles could be the result from the mechanics of the setup, or in fact that anyone understands this.

I think #3 here is where we have the most problem
Best review by looking at just a little of the mechanics in:
http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/spectrum.html

In the graphic of the cones of light coming from the converter, we can see the points light is picked up from to filter and feed into fiber 1 and fiber 2.
If we go to points above any of the intersection points in the top circles to pick up light - we will call them PH.
And likewise below in the bottom circles of the cones of light calling light from that area PV.
Testing of just the light from points in PH for polarization would reveal light from that area is always Horizontal or aligned at 90 degrees.
And light from points in the PV area would always test for polarization as Vertical or aligned at 0 degrees.
Rotating our test off that alingment would decrease the light passed till reaching non passing at 90 degrees out of alignment for this very simple test. (Where if the polarization alignment was random though 360 degrees for PV and PH this test would always show a 50% passage of light as each is tested individually).

Thus when carefully picking out light at the intersection points you can only know that it is not any other angle than H or V. But which one of ether 0 or 90 cannot be known until tested.
Is this a correct interpretation of your #3 above and the graphic.


Also in the link you had originally provided:
[PLAIN]http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/entangle.html[/URL]
The graph of results does not make sense to me unless the scale of the bottom alignment angles is doubled for the Blue line. And for the Red line the scale doubled and 22.5 subtracted. Otherwise they results seem to indicate 100 correlation with only a 45 degree separation between to two observers.
Have they posted there data poorly, or is there something I'm missing??

 

[DrChinese]

1. I think #3 here is where we have the most problem
Best review by looking at just a little of the mechanics in:
http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/spectrum.html

In the graphic of the cones of light coming from the converter, we can see the points light is picked up from to filter and feed into fiber 1 and fiber 2.
If we go to points above any of the intersection points in the top circles to pick up light - we will call them PH.
And likewise below in the bottom circles of the cones of light calling light from that area PV.
Testing of just the light from points in PH for polarization would reveal light from that area is always Horizontal or aligned at 90 degrees.
And light from points in the PV area would always test for polarization as Vertical or aligned at 0 degrees.
Rotating our test off that alingment would decrease the light passed till reaching non passing at 90 degrees out of alignment for this very simple test. (Where if the polarization alignment was random though 360 degrees for PV and PH this test would always show a 50% passage of light as each is tested individually).

Thus when carefully picking out light at the intersection points you can only know that it is not any other angle than H or V. But which one of ether 0 or 90 cannot be known until tested.
Is this a correct interpretation of your #3 above and the graphic.


2. Also in the link you had originally provided:
[PLAIN]http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/entangle.html[/URL]
The graph of results does not make sense to me unless the scale of the bottom alignment angles is doubled for the Blue line. And for the Red line the scale doubled and 22.5 subtracted. Otherwise they results seem to indicate 100 correlation with only a 45 degree separation between to two observers.
Have they posted there data poorly, or is there something I'm missing??

1. Looking at the cones at http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/down.html might lead you to think that the polarization is known for the signal and idler beams, but it isn't. The \psi formula shows that we are looking at a mixed state.

Once the photon pairs are in a superposition, anything you knew earlier is no longer relevant. The H and V designation loses its meaning in any absolute sense. If the photon orientation was known already, subsequent measurements would actually be superfluous.

2. It looks like the scale is off to my eyes as well.

 

[RandallB]

1. Looking at the cones at http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/down.html might lead you to think that the polarization is known for the signal and idler beams, but it isn't. The \psi formula shows that we are looking at a mixed state.

Once the photon pairs are in a superposition, anything you knew earlier is no longer relevant. The H and V designation loses its meaning in any absolute sense. If the photon orientation was known already, subsequent measurements would actually be superfluous.

2. It looks like the scale is off to my eyes as well.

Sorry, Dr that is not going to do - some formula for \psi that I cannot derive is not satisfactory. What I ask is very simple:

The stream of light coming, from the area I'd described as PH, i.e. parts of the upper cone well away from any intersection or overlap with the other cone.
With only that light being routed through a polar filter. And then rotating that filter through 360 degrees, what do you get?
I can only see two possible results -
A) light is reduced by 50% for any angles during this solo test.
Or B) Light pass 100% on an angle H and 0% on the relative V angle.
And would follow the same result for the red and blue shift light tested separately, or both together.
Based on the diagram, it looks like they say B is true.

This is so simple and easy to do that:
Any test or tester that refuses to even look at, know, or share what that information is, (Along with any notes they may care to share about it) is not following a scientific method.
And has no credibility to use the tool they are describing for anything.

So it it A or B.?


Also, for the whoever put together the above web pages for the proposes of their test what is the "signal" and the "idler". I thought those were terms as in idler goes to area A and signal goes to area B (and also C when ready for that part of the test). They don't seem to use those terms in that manner. How are the intersection points 1 and 2, that they use for testing, then to be described if not as "signal" and "idler"?

 

[Cat]

The stream of light coming, from the area I'd described as PH, i.e. parts of the upper cone well away from any intersection or overlap with the other cone.
With only that light being routed through a polar filter. And then rotating that filter through 360 degrees, what do you get?
I can only see two possible results -
A) light is reduced by 50% for any angles during this solo test.
Or B) Light pass 100% on an angle H and 0% on the relative V angle.
And would follow the same result for the red and blue shift light tested separately, or both together.
Based on the diagram, it looks like they say B is true.

I'm sure you're right. It is only at the points of intersection of the cones that we are supposed to have "entangled photons".

The setup seems to be basically one introduced a few years ago by Kwiat et al. I've always had my doubts about what is actually measured -- there seems a possibility that in fact you usually get both H and V occurring together and what matters is the phase difference. I've just downloaded one of the refs and will check if this newer setup gives any more clues.

... Also, for the whoever put together the above web pages for the proposes of their test what is the "signal" and the "idler". I thought those were terms as in idler goes to area A and signal goes to area B (and also C when ready for that part of the test). They don't seem to use those terms in that manner. How are the intersection points 1 and 2, that they use for testing, then to be described if not as "signal" and "idler"?

The terms "signal" and "idler" are just the conventional ones used for the two differently polarised beams output by a nonlinear crystal. There is no logical difference between beams 1 and 2.

Cat

 

[Hans de Vries]

I'm sure you're right. It is only at the points of intersection of the cones that we are supposed to have "entangled photons".

The setup seems to be basically one introduced a few years ago by Kwiat et al. I've always had my doubts about what is actually measured -- there seems a possibility that in fact you usually get both H and V occurring together and what matters is the phase difference. I've just downloaded one of the refs and will check if this newer setup gives any more clues.

The terms "signal" and "idler" are just the conventional ones used for the two differently polarised beams output by a nonlinear crystal. There is no logical difference between beams 1 and 2.

Cat

To be a bit more complete:

A photon on one cone is supposed to be entangled with a photon on the
other cone. The positions are mirrored with respect to the central beam.
Following from momentum/energy conservation.

All photons in a cone are equally polarized, Horizontal on one cone and
vertical in the other. It's only at the intersections that the polarization
can either be horizontal and vertical or both.

The polariztion is fixed by the optical axis of the BBO crystal. only H
and V occur. The BBO PDC looks somewhat like a normal prism beam
splitter with an ordinary and an extra-ordinary ray. However it's non-
linear and gives off a whole spectrum of light. The light in a cone is
mono-chromatic. Larger and smaller cones have different frequencies.


Regards, Hans

 

[RandallB]

Bell fails to disprove EPR.

To be a bit more complete:
A photon on one cone is supposed to be entangled with a photon on the
other cone. The positions are mirrored with respect to the central beam.
Following from momentum/energy conservation.
All photons in a cone are equally polarized, Horizontal on one cone and
vertical in the other. Regards, Hans

I also did find how the "half Wave filter" does work as I'd guessed and the scale shows the angle of the filter only, to get the angle of polarization, adjustment to that scale is needed.
I wish they would have used 12.25 degrees for a 22.5 shift instead of 45.
But by comparing with what a manual non-"entangled" test would do, the "LR" is correctly predicting the same as the QM for the A-C test. And Bell's approach to not allow the LR to use that prediction is just silly.

MUCH MORE significant is back at the A-B test. Here it's assumed that ALL Agree on 100% correlation. Bell depends on this agreement! - But when compared with the "non-QM" prediction including -45 & +45 degrees for the A-B test in a manual non-"entangled" test for cross checking. It's clear the best that can be hoped for is 75% correlation! The "LR" can only agree to 100% at the A-B level if it agrees with entanglement - what sense would that make?

BELL vs. EPR is just noise in my opinion. The issue is test results at A-B gives 100%! And is the assumption of QM. While "Non-QM" currently cannot, or has not shown, how it can make such a prediction. A much clearer and obvious conflict (or I should say issue) than Bell Statistics. EPR just has not tried to explain yet - but belives a better than FTL, that QM requires, explanation exists.

Randall B

 

[DrChinese]

This is so simple and easy to do that:
Any test or tester that refuses to even look at, know, or share what that information is, (Along with any notes they may care to share about it) is not following a scientific method.
And has no credibility to use the tool they are describing for anything.

You are diving into the deep end here. Published papers are intended for other professionals. Relevant information is freely available for those who are willing to invest the effort - whether you are pro or amateur. You are not the primary audience for such professionals, and so your criticism is meaningless. Even you should know better.

Your concept of LR vs. QM is well off the mark as well. LR has more baggage than QM, as Bell demonstrated amply. QM makes specific fixed predictions, which are born out experimentally at any angle. That makes it way different than LR, which can only match QM at certain specific angles depending on which version of LR you subscribe to. So far you have kicked at the bucket, but I haven't seen it move yet.

 

[RandallB]

You are diving into the deep end here. Published papers are intended for other professionals. Relevant information is freely available for those who are willing to invest the effort - whether you are pro or amateur. You are not the primary audience for such professionals, and so your criticism is meaningless. Even you should know better.

Your concept of LR vs. QM is well off the mark as well. LR has more baggage than QM, as Bell demonstrated amply. QM makes specific fixed predictions, which are born out experimentally at any angle. That makes it way different than LR, which can only match QM at certain specific angles depending on which version of LR you subscribe to. So far you have kicked at the bucket, but I haven't seen it move yet.

Well if the “deep end” is the same side of the pool as Dr E, Dr P, and Dr R I won’t feel to bad about it.

All I’m saying is I see lots of proclamations for “disproving” EPR with Bell by various large standard deviation factors. BUT then the claim is that most any LR prediction is a violation of BELL. -- So how did they figure the # of standard deviations without having a clear LR prediction?

Now I think they, Plus you and I, agree that Bell depends on ALL Agreeing to expect 100% correlation for the A-B test.
But if the LR does agree with this – It’s not that I have another “version” of the LR. It’s that I cannot figure who he is at all.
Here’s why:
On this point I think you and I agree; that IF a 3rd party manually simulates a test with unknown but NOT entangled polarized photons separated by 90 degrees (type II) the result of running the A-B test is going to be 75% (not 100%) correlation with A-B (fixed at 90) rotating through 360.
SO THE POINT IS – on what bases can a LR assume that when the real test is brought online he should predict 100% for the A-B part?? He needs a reason other than FTL action at a distance. I haven’t seen anyone state one yet. If I cannot get this off 75% and up to 100% I don’t see how I can apply Bell at all, let alone expect it amply proves something.

As I said back in post #112 this is a much more significant discrepancy to be resolved than the arguments over BELL vs. “loopholes” etc. Actual test gives 100% correlation at A-B, best non-QM prediction 75%.

Ether 1) There is a simple reason for a LR expecting 100% at the A-B test that has totally slipped by me.
OR 2) Or that some theroy improvement of the current explanation given by QM should be able to be found as EPR expects. (EPR does not assume that QM is wrong as far as I know)

THAT’s the only bucket I see, And I don’t see where you’ve even looked into it yet; let alone take a kick at it.

Do you want to 1) come up with that reason why LR sees 100% at A-B ??
Or should I come up with a theory for 2) ??

Randall B

 

[DrChinese]

1. All I’m saying is I see lots of proclamations for “disproving” EPR with Bell by various large standard deviation factors. BUT then the claim is that most any LR prediction is a violation of BELL. -- So how did they figure the # of standard deviations without having a clear LR prediction?

2. Now I think they, Plus you and I, agree that Bell depends on ALL Agreeing to expect 100% correlation for the A-B test.
But if the LR does agree with this – It’s not that I have another “version” of the LR. It’s that I cannot figure who he is at all.
Here’s why:

3. On this point I think you and I agree; that IF a 3rd party manually simulates a test with unknown but NOT entangled polarized photons separated by 90 degrees (type II) the result of running the A-B test is going to be 75% (not 100%) correlation with A-B (fixed at 90) rotating through 360.

SO THE POINT IS – on what bases can a LR assume that when the real test is brought online he should predict 100% for the A-B part?? He needs a reason other than FTL action at a distance. I haven’t seen anyone state one yet. If I cannot get this off 75% and up to 100% I don’t see how I can apply Bell at all, let alone expect it amply proves something.

As I said back in post #112 this is a much more significant discrepancy to be resolved than the arguments over BELL vs. “loopholes” etc. Actual test gives 100% correlation at A-B, best non-QM prediction 75%.

Ether 1) There is a simple reason for a LR expecting 100% at the A-B test that has totally slipped by me.
OR 2) Or that some theroy improvement of the current explanation given by QM should be able to be found as EPR expects. (EPR does not assume that QM is wrong as far as I know)

THAT’s the only bucket I see, And I don’t see where you’ve even looked into it yet; let alone take a kick at it.

Do you want to 1) come up with that reason why LR sees 100% at A-B ??
Or should I come up with a theory for 2) ??

Randall B

1. Good, I agree this is a fruitful area to focus in. You ask the question - how do they figure the standard deviations without having a specific LR theory to compare against? The answer is simple: the standard deviations are calculated against the Bell inequality at specific angles. The inequality deviates from QM at some angles more than others. And at some angles there is no difference between the inequality and QM. 0, 45 and 90 degrees are such angles where there is no difference at all.

So, IF YOU POSTULATE an LR that exactly matches the inequality function, that is as close as you can come to QM's predictions with an LR. No one (seriously) is really saying that the Bell inequality function itself is an LR theory. That is merely "as good as it gets". The standard deviations are usually quoted relative to the angles at which the difference is maximal - normally 22.5 degrees. See the graph of: QM versus the Inequality.

Because, you see, it possible simply to assert the following 3 cases for LRA theories:

i) You have a LR that makes the same predictions as QM! But that immediately runs afoul of the Bell inequality.

ii) You can assert that you have an LR that exactly matches the Bell inequality function as pictured; but that is ruled out experimentally by X standard deviations etc. etc. as we have already discussed; but at least you get to make the same predictions as QM at some angles. So in this case, you agree there is entaglement but not quite as much as QM predicts.

iii) You can do as Cat does, postulate an LR that is even FARTHER away from QM and FARTHER from the Bell inequality too. Obviously that will be ruled out by experiment by many more standard deviations than ii) above will. Hers is the LR theory - just one of an infinite array of possibilities - that says there is no entanglement at all. Then you get the 75% prediction instead of 100% when there is maximum correlation.

Bell's work was critical because it showed that there is NO WAY to come up with an LR that exactly matches QM's predictions. Once you follow the logic of Bell, it is pretty hard (i.e. impossible unless you are in major denial) to hold onto LR while supporting the predictions of QM.

2. 3. So the simple reason for 100% for LR when correlated is that is an angle at which there is no violation of the inequality. But you can have LRs give different values, as I mentioned. Bell applies to LR theories and acts to limit their predictions; the Bell inequality is a theoretical argument but it works because it uses the predictions of QM as a guidepost. To simply summarize:

There is no LR theory possible which matches QM at all angles AND respects the Bell Inequality. If it does not respect the Bell Inequality boundary condition, then it is not local realistic. If it does not match the predictions of QM then it is falsified by experiment.

 

[RandallB]

2. 3. So the simple reason for 100% for LR when correlated is that is an angle at which there is no violation of the inequality. But you can have LRs give different values, as I mentioned. ……

iii) You can do as Cat does ….., Hers is the LR theory - - - - that says there is no entanglement at all. Then you get the 75% prediction instead of 100% when there is maximum correlation. .

Ok, piecing together your comments as above, you seem to be tracking with me a little better. You had seemed to be stuck on the A-B test (0 degrees) MUST have a 100% correlation for the LR.
But, IF that is just the most popular interpretation of the LR as it probably makes the best looking inequality graph (like the one you linked).
AND given I cannot envision how any non-entangled view I’ve seen can give 100% at 0 degrees.
THEN I should not expect the popular views on Standard Deviations or inequality graphs to be meaningful to me.

I’m satisfied that under current Classical and/or Wave theory the only prediction that can be made at 0 degrees is 75% correlation.
Thus from such a view, I don’t need Bell to tell me that LR / EPR is not matching QM’s ability to predict the results of this test right?
That’s my main point – what did I need BELL for? – I can already see the QM is outperforming the other predictors.
Just as a matter of curiosity – do you know of a rational LR explanation to make a convincing claim at 100% at 0 degrees?
Only then do I see a need to even worry about using BELL at all.
DO YOU SEE MY POINT?

I do disagree with the idea:
“that there is NO WAY to come up with an LR that exactly matches QM's predictions”
We are trying to explain the results of the test, not to match other theories. We have one theory that does, QM, That does not necessarily mean additions or alternatives are excluded.

But I do have to agree with your carefully worded:

There is no LR theory possible which matches QM at all angles AND respects the Bell Inequality.

Just that the ONLY WAY for the EPR position to hold, is to find a theory or extension to current theory, that 1)can explain test results as well as QM’s. PLUS 2)the foundation to the theory must preclude the ability to use BELL as a disqualifier as does QM. AND 3) explain why what currently looks like FTL activity in fact is not FTL.
I believe if a theory cannot clearly, and convincing revise the prediction at 0 degrees from 75% up to 100% it has no shot at the above 3 conditions.

I think were together on the above? Do you agree? If not, where not?

 

[DrChinese]

Ok, piecing together your comments as above, you seem to be tracking with me a little better. You had seemed to be stuck on the A-B test (0 degrees) MUST have a 100% correlation for the LR.
But, IF that is just the most popular interpretation of the LR as it probably makes the best looking inequality graph (like the one you linked).
AND given I cannot envision how any non-entangled view I’ve seen can give 100% at 0 degrees.
THEN I should not expect the popular views on Standard Deviations or inequality graphs to be meaningful to me.

I’m satisfied that under current Classical and/or Wave theory the only prediction that can be made at 0 degrees is 75% correlation.
Thus from such a view, I don’t need Bell to tell me that LR / EPR is not matching QM’s ability to predict the results of this test right?
That’s my main point – what did I need BELL for? – I can already see the QM is outperforming the other predictors.
Just as a matter of curiosity – do you know of a rational LR explanation to make a convincing claim at 100% at 0 degrees?
Only then do I see a need to even worry about using BELL at all.

1. DO YOU SEE MY POINT?

2. I do disagree with the idea:
“that there is NO WAY to come up with an LR that exactly matches QM's predictions”

We are trying to explain the results of the test, not to match other theories. We have one theory that does, QM, That does not necessarily mean additions or alternatives are excluded.

But I do have to agree with your carefully worded: Just that the ONLY WAY for the EPR position to hold, is to find a theory or extension to current theory, that 1)can explain test results as well as QM’s. PLUS 2)the foundation to the theory must preclude the ability to use BELL as a disqualifier as does QM. AND 3) explain why what currently looks like FTL activity in fact is not FTL.
I believe if a theory cannot clearly, and convincing revise the prediction at 0 degrees from 75% up to 100% it has no shot at the above 3 conditions.

I think were together on the above? Do you agree? If not, where not?

1. If you don't want to match the predictions of QM (i.e. you think 75% correlation at 0 degrees is reasonable), then you are right: you don't need Bell you that there is a conflict.

2. You can construct a local realistic theory that gives 100% correlation at 0 degrees. But you can't match QM's other predicted angle values with such a theory. I know this because of the Bell Theorem. You are welcome to try, but you will find every time that one provision or another will jump into consideration.

 

[Cat]

2. You can construct a local realistic theory that gives 100% correlation at 0 degrees. But you can't match QM's other predicted angle values with such a theory. I know this because of the Bell Theorem. You are welcome to try, but you will find every time that one provision or another will jump into consideration.

If we want to match observation, I don't think we need our LR theory to necessarily give "100% correlation" at 0 degrees. It all depends how you measure it! Because of low detector efficiency, the actual probabilities of detection even at 0 deg have never been anywhere near to 100%. The only way people have got the idea that it is in fact achieved is that all the data they see has been ''normalised''.

I suspect that in recent Bell test experiments there is in addition another factor to be born in mind: that they probably don't have the rotational invariance that the QM formula assumes. This was illustrated to some extent in a graph from a link that I think it was you who provided, where the range of coincidences when one detector was set at 0 deg was slightly different from that when it was set at 22.5 deg. If the setup lacked it ''completely'', e.g if all the light concerned were in fact polarised vertically, the observed coincidences (given perfect detectors) would, I think, ''exactly'' match the QM prediction when one detector was fixed at 0 deg. And there is another possibility: if half were polarised V and half H but the ''same'' choice was made on each side of a Bell test experiment, as far as the coincidences were concerned you would again get apparently perfect agreement with QM for the "correct" choice of the fixed setting.

Incidentally, I don't think we've got to the bottom of what actually happens in that experiment. There is something odd about the way in which the polarisation is measured ... must look up the link ... an involvement of the relative phase of V and H components, as in Weihs' experiment?

PS: Found the link. It is http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/entangle.html/

Cat

 

[Cat]

There is no such photon state as you describe. A photon cannot be polarized either H or V (unknown and definite) and still be at 0 or 90 degrees. If you don't know, you don't know. Once you do know, you know.

To say it a different way... There is nothing special about 0 and 90 degrees. So there is no angle at which you can set a second set of polarizers and get any different correlation results. You are just as free to call any results as H and V. As always in all EPR tests, it is the angle between the 2 measuring polarizers that controls correlation results and nothing else.

I was looking back to try and find that link with the graph and came across this message. The graph disproves your statement! The choice of fixed detector angle does make a difference, not just the angle between detectors.

Cat

 

[DrChinese]

I was looking back to try and find that link with the graph and came across this message. The graph disproves your statement! The choice of fixed detector angle does make a difference, not just the angle between detectors.

Cat

I couldn't find any graph like the one you described. The link has a number of different slides... can you tell me which one I should reference? I have noticed this link has a bit of difficulty because it seems to come up with different slides for different people. Is it the one where psi2 is measured at 0 and 22.5 degrees?

 

[RandallB]

Dr C
Cat is referring to the link you originally provided in post #119
http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/entangle.html
(Not sure what wrong with Cat’s link)
This is the one where “in our eyes” the scale seemed off. Your post #128
The scale measures the angle of the ½ wave filter; to translate to polarization angles, the bottom alignment angles need to be doubled! Thus we get 100% correlation at 0 and 90 degrees and also at 45 and 135 (AKA -45) degrees.

Now as Hans pointed out in his post #131. The most important part of the “Spectral Distribution” page of this site is how it shows that “Entanglement” can exist with KNOWN polarities, in areas of the cones not on the intersections!. Testing will show the cones produce FIXED polarity photons in the “known” areas. And I’m quite satisfied that testing on entanglement points not on the intersections (‘entanglement’ with known polarities) will successfully produce the same results as on the “Entanglement” page.

QM still has no problem using the \psi formula to predict 100% for both 0/90 and 45/-45 in an A-B test.
But that formula is NOT available to the LR.!
The LR must get 100% at 0/90, But I see 50% as the only option for the 45/-45 part of the A-B test for the LR. For a net 75% LR prediction on the A-B test! I’ve been unable to find any justification for any other LR prediction. And this prediction would be the same for known and unknown polarity with ‘entanglement. Now since the Bell proof relies on a 100% prediction by the LR for A-B testing, I don’t see how I can accept Bell.

Although the tests results posted on that Web site are more directed at using Bell to confirm the quality of their method of producing “Entanglement”. There is enough raw data there to convince me that Bell does not satisfy rejecting EPR.
But rather that the A-B test, standing on its own with no need to even run the A-C part (or use BELL), most clearly demonstrates that there is a huge and unresolved conflict (75% vs. 100%) between EPR and QM.

So as you put it:

2. You can construct a local realistic theory that gives 100% correlation at 0 degrees.

AND only if such a theory is used, is Bell useful!
It’s a mystery to me, what is that LR theory that gives 100% during the A-B test?

 

[DrChinese]

Dr C
Cat is referring to the link you originally provided in post #119
http://scotty.quantum.physik.uni-muenchen.de/exp/psrc/entangle.html
(Not sure what wrong with Cat’s link)
This is the one where “in our eyes” the scale seemed off. Your post #128
The scale measures the angle of the ½ wave filter; to translate to polarization angles, the bottom alignment angles need to be doubled! Thus we get 100% correlation at 0 and 90 degrees and also at 45 and 135 (AKA -45) degrees.

Now as Hans pointed out in his post #131. The most important part of the “Spectral Distribution” page of this site is how it shows that “Entanglement” can exist with KNOWN polarities, in areas of the cones not on the intersections!. Testing will show the cones produce FIXED polarity photons in the “known” areas. And I’m quite satisfied that testing on entanglement points not on the intersections (‘entanglement’ with known polarities) will successfully produce the same results as on the “Entanglement” page.

QM still has no problem using the \psi formula to predict 100% for both 0/90 and 45/-45 in an A-B test.
But that formula is NOT available to the LR.!
The LR must get 100% at 0/90, But I see 50% as the only option for the 45/-45 part of the A-B test for the LR. For a net 75% LR prediction on the A-B test! I’ve been unable to find any justification for any other LR prediction. And this prediction would be the same for known and unknown polarity with ‘entanglement. Now since the Bell proof relies on a 100% prediction by the LR for A-B testing, I don’t see how I can accept Bell.

Although the tests results posted on that Web site are more directed at using Bell to confirm the quality of their method of producing “Entanglement”. There is enough raw data there to convince me that Bell does not satisfy rejecting EPR.
But rather that the A-B test, standing on its own with no need to even run the A-C part (or use BELL), most clearly demonstrates that there is a huge and unresolved conflict (75% vs. 100%) between EPR and QM.

So as you put it:
AND only if such a theory is used, is Bell useful!
It’s a mystery to me, what is that LR theory that gives 100% during the A-B test?

We're wandering all over the place here.

First, I didn't write this page per the link. To the extent it is useful, great. It is just a picture so don't get caught up in a literal interpretation. If the scale is off, it is off.

The question for Bell is absolutely NOT can a LR theory that YOU think up give a 100% prediction at 0 degrees. Plenty of folks - Einstein among them - have simply assumed that the probabilistic predictions of QM are correct. Eisntein was also one of the fathers of quantum theory, as you may recall. So he was quite ambivalent about QM. But I don't think you will ever find a reference from him doubting that the statistical spin predictions of QM as simply wrong.

Bell always assumed that the predictions of QM were correct. Almost everyone did. I cannot recall any serious proponent of the position - ever - that QM would yield a wrong prediction in this regard. I am sure plenty of folks held an open mind, but cannot recall anyone actually voicing the expectation that QM was incorrect. You may question it certainly between the period 1935 to 1981 (when Aspect effectively shut the door for good) but most others never gave it as much thought. QM was simply too good.

As previously stated, the point of Bell was to demonstrate - to those who thought the predictions of QM could be neatly accommodated by some to-be-determined future LR theory - that they were flat wrong. If you don't hold this position, then Bell is not for you. Since plenty of famous physicists DID hold such a view, the Bell paper did matter. Today it is widely referenced.

You still cannot support local reality. Per your logic, LR cannot do better than 75% at 0 degrees. Fine. The experimental evidence is 100% so your LR is ruled out, end of subject. You are trying to apply logic to the LR position, and the true LR position all along has been "we will discover the truth in the future to prove our position correct". After Bell that position fell apart and no experiment was needed to cause it to fall apart. You cannot have your cake and eat it too.

As to the PDC cones: if the cones generate fixed polarization outside the area of intersection, also fine. The photons are not entangled there and those photons are masked out of the test. Once you have a mixed state (where there is intersection) then all bets are off. It is the entangled states we want to measure.

Realistically, you should ignore the entire concept of the 75% case, which is throwing you off track. That case ignores entanglement in favor of a naive realism! No one takes it seriously much except those who deny the science of Bell tests, such as Cat, who also deny entanglement, Aspect, double slits, HUP, photons and in most respects the essential philosophy of QM. Cat, have I mistated your postion? :)

 

[Cat]

I couldn't find any graph like the one you described. The link has a number of different slides... can you tell me which one I should reference? I have noticed this link has a bit of difficulty because it seems to come up with different slides for different people. Is it the one where psi2 is measured at 0 and 22.5 degrees?

Yes, that's the one. RandallB has given the correct link: http://scotty.quantum.physik.uni-mu...c/entangle.html .

The difference is not very great but it seems definite enough: the ranges of the two curves are not the same. On its own this might not mean much but, if I remember correctly, we find the same kind of discrepancy in Weihs' graphs. I think this could have the same cause.

A hint as to the explanation of the scale problem is given in Weihs' paper: there are two angular values involved: a phase angle and a geometrical one. A phase difference of 180 deg between H and V components shows up as a geometrical difference of 90 deg in the output from a Wollaston prism. This is a classical wave result, as he says in one of his footnotes.

Cat

 

[RandallB]

We're wandering all over the place here.
----
As to the PDC cones: if the cones generate fixed polarization outside the area of intersection, also fine. The photons are not entangled there and those photons are masked out of the test. Once you have a mixed state (where there is intersection) then all bets are off. It is the entangled states we want to measure.

Realistically, you should ignore the entire concept of the 75% case, which is throwing you off track.

This is the area to focus on to avoid wandering all over.
75% vs 100% is important.

As Hans, I believe the area outside of the intersection DOES provide "entangled" photons and "fixed". See post #131 by Hans. And as I said IF the test is run in the non-intersection area the same 100% correlation will be found when aligned on correct "entangled" points.
I understand that QM-BELL would not expect a result of "entanglement" with KNOWN polierzations. Just as the LR should expect no better tha 75%. Thus IF the result is found to be so, I believe that it would disprove QM-BELL. At least in the photon polarization case, but would not give an opinion on QM alone.

If there is "entanglement" with known polierzations, it could well mean that "entanglement may not really be Entanglement but the result of SOMETHING ELSE that needs a better explanation than we currently have. That is the EPR point.

So is "entanglement" with known polierzations real?
The raw data in the website we are looking at is not directed at answering that question, as they do not show any direct attempt to find them outside the intersections. I know Cat seems to question the value of the data in whole. But for me there is just barely enough data to convice me it is true. I understand for you it may not be enough data to convice you.

SO can we both agree that IF and only IF someone someday can successfully produce 100% correlation in a A-B test for photons outside the intersections, and of cource verify fixed polarization (ie. "entanglement" with known polierzations). That QM-Bell, at least within the photon polarization area, is in trouble?

RB