Bell's theorem proof. Does it really proofs anything?

[0xDEAD BEEF]

So here is this thing that i really really can not agree with (regarding experiments)! What Bell's theory states (correct me, if i am wrong) and experiments with SPOT detector tend to prove is, that measurement of spin of one twin-light photon affects spin of other. Well - if we assume that then results of this experiment agree with predicted results of theory. However - i see no way how this theory rules out theory of "hidden variable".

One can also assume, that both twin-photons have defined spin from very beginning. If we describe spin not as "angle" but as most-highest spin direction, then these test results would also describe theory in which photon carries more information than just it's spin (as angle). In such case this measurement with angles 60 degrees made of -30 and +30 (50% and 50%) actually is same measurement as 0 and 30 degrees so as expected, error is 25% (100 - 75%).

Said that - this experiment proves NOTHING about measurement of spin impacting spin of other photon.

http://quantumtantra.com/bell2.html

Please help me out with this!


Beef

 

[chronon]

I think you should stop worrying about angles. Looking at the diagram showing the 4 different measurement possibilities, there is nothing which says the properties of the photons are represented as angles. It's the detectors which have different possible angle settings. But even then the angles are not vital to the argument. Alice could have a detector with settings marked 0 and + and Bob with - and 0. Then the 4 possible settings and the difference between results are:

AB : Difference
00 : 0%
+0 : 25%
0- : 25%
+- : 75%

Assuming locality, the difference for +- can't possibly be more than the sum of the differences for +0 and 0-

 

[0xDEAD BEEF]

Please be more "specific". I really did not understand your idea. What i see is - this could be easily explained by photons having "angle vector" not by detectors by any means affecting measurement results.

I see this experiment results - conclusions as misintrepreation of cause and effect.

Beefs

 

[DrChinese]

One can also assume, that both twin-photons have defined spin from very beginning.

The problem you face is that there is NO data set which you can provide which will match experimental results. I think if you attempt to produce one, you will quickly see the problem. Any rule set you provide - in which the hidden values are independent of the measuring device settings for Alice and Bob - will not be able to match the predictions of QM.

So that means that either there are no predefined values, or there is FTL communication between the twins.

 

[0xDEAD BEEF]

I strongly disagree! In fact - there is data set and rulles, that i can apply, which will exactly match experiment results! Could you please describe experiment results, because ones provided in that web page i just posted seems too trivial to work with. Any normal distribution function for spin value would predict these results!

Edit: In fact - to work properly with these results one would also need exact placement of sensors used in this experiment. As well - one would need exact knowledge of crystal used for directing polarized light. What i see from these results - NOTHING! And i mean - NOTHING! I see two photons with same spin being analyzed twice! I see big misinterpretation of data. And i see BIG BIG problems with logic used there. Either i am totaly stupid or something is very wrong here! (btw - i am not THAT stupid)

Beef

 

[Cthugha]

Either i am totaly stupid or something is very wrong here!

Well, the first thing that comes to my mind is, that it might not be the best idea to discuss Bell's theorem based on the information on a page entitled quantum tantra, run by a guy who claims quantum tantra to be a brand new way of doing science and who also claims to be the author of books with high credibility titles such as "Quantum Reality", "Faster Than Light" and "Elemental Mind". I suggest you learn a bit about Bell's theorem from a more credible source (the link in DrChinese's signature for example will take you to one) and then return to discuss based on the complete story.

 

[0xDEAD BEEF]

Yes! Exactly!
But anyway - i see this as simplified explanation. Problem is - i am not willing to accept this on results based on that page. How i see photon is (lets look at it from front) as wave front traveling through space. Polarized wave would mean, that this round wave is "cut". If so - these experiments can be explained by "hidden variable" which is "polarization" strength for different angles. Are there any experiments which prove, that photon has single polarization direction (thus - it is not field where polarization actualy is vector of many summs?)

Please help me out since this makes NO sense to me at all!
Beef

 

[JesseM]

I strongly disagree! In fact - there is data set and rulles, that i can apply, which will exactly match experiment results! Could you please describe experiment results, because ones provided in that web page i just posted seems too trivial to work with. Any normal distribution function for spin value would predict these results!

From an old post, a simple analogy I came up with illustrating why assuming pre-existing values for the variables doesn't work:

Suppose we have a machine that generates pairs of scratch lotto cards, each of which has three boxes that, when scratched, can reveal either a cherry or a lemon. We give one card to Alice and one to Bob, and each scratches only one of the three boxes. When we repeat this many times, we find that whenever they both pick the same box to scratch, they always get the same result--if Bob scratches box A and finds a cherry, and Alice scratches box A on her card, she's guaranteed to find a cherry too.

Classically, we might explain this by supposing that there is definitely either a cherry or a lemon in each box, even though we don't reveal it until we scratch it, and that the machine prints pairs of cards in such a way that the "hidden" fruit in a given box of one card always matches the hidden fruit in the same box of the other card. If we represent cherries as + and lemons as -, so that a B+ card would represent one where box B's hidden fruit is a cherry, then the classical assumption is that each card's +'s and -'s are the same as the other--if the first card was created with hidden fruits A+,B+,C-, then the other card must also have been created with the hidden fruits A+,B+,C-.

The problem is that if this were true, it would force you to the conclusion that on those trials where Alice and Bob picked different boxes to scratch, they should find the same fruit on at least 1/3 of the trials. For example, if we imagine Bob and Alice's cards each have the hidden fruits A+,B-,C+, then we can look at each possible way that Alice and Bob can randomly choose different boxes to scratch, and what the results would be:

Bob picks A, Alice picks B: opposite results (Bob gets a cherry, Alice gets a lemon)

Bob picks A, Alice picks C: same results (Bob gets a cherry, Alice gets a cherry)

Bob picks B, Alice picks A: opposite results (Bob gets a lemon, Alice gets a cherry)

Bob picks B, Alice picks C: opposite results (Bob gets a lemon, Alice gets a cherry)

Bob picks C, Alice picks A: same results (Bob gets a cherry, Alice gets a cherry)

Bob picks C, Alice picks picks B: opposite results (Bob gets a cherry, Alice gets a lemon)

In this case, you can see that in 1/3 of trials where they pick different boxes, they should get the same results. You'd get the same answer if you assumed any other preexisting state where there are two fruits of one type and one of the other, like A+,B+,C- or A+,B-,C-. On the other hand, if you assume a state where each card has the same fruit behind all three boxes, so either they're both getting A+,B+,C+ or they're both getting A-,B-,C-, then of course even if Alice and Bob pick different boxes to scratch they're guaranteed to get the same fruits with probability 1. So if you imagine that when multiple pairs of cards are generated by the machine, some fraction of pairs are created in inhomogoneous preexisting states like A+,B-,C- while other pairs are created in homogoneous preexisting states like A+,B+,C+, then the probability of getting the same fruits when you scratch different boxes should be somewhere between 1/3 and 1. 1/3 is the lower bound, though--even if 100% of all the pairs were created in inhomogoneous preexisting states, it wouldn't make sense for you to get the same answers in less than 1/3 of trials where you scratch different boxes, provided you assume that each card has such a preexisting state with "hidden fruits" in each box.

But now suppose Alice and Bob look at all the trials where they picked different boxes, and found that they only got the same fruits 1/4 of the time! That would be the violation of Bell's inequality, and something equivalent actually can happen when you measure the spin of entangled photons along one of three different possible axes. So in this example, it seems we can't resolve the mystery by just assuming the machine creates two cards with definite "hidden fruits" behind each box, such that the two cards always have the same fruits in a given box.

 

[0xDEAD BEEF]

No!
That would not be violation at all! In fact - there are rulles! You can not separate those two systems! There is no violation! There is ERROR in logic!

So you say - when they picked different boxes, they found out that they only got same fruits 1/4 of time? But of course! Because it is a rule that same boxes have same card on them! BUT also it is a rule, that two boxes have different card on them! Let's quickly go through all possilbe combinations -
(aa), ab, ac, ba, (bb), bc, ca, cb, (cc). 9 options. 1/3 of them has same card (match). But we have to take out these matches since we are not looking at them.
So we are left with (ab?, ac?), (ba?, bc?), (ca?, cb?) - so - one would expect, that we should get pretty good chance that either of them maches. HEY - but we have FORGOTEN about another rule! There allways are two different pairs because of nature of photons!
(next post)

 

[DrChinese]

How i see photon is (lets look at it from front) as wave front traveling through space. Polarized wave would mean, that this round wave is "cut". If so - these experiments can be explained by "hidden variable" which is "polarization" strength for different angles.

Your problem begins with the fact that such explanation does not match experimental results. You will see this as you answer a series of questions.

If a photon is polarized at 0 degrees, what is the likelihood that it will pass a polarizer at 45 degrees? Is that too pre-determined (even if we do not whether it will or won't) ?

-------------------

By the way, your ongoing commentary about "Either i am totaly stupid or something is very wrong here!" is out of place. It is common courtesy to post politely while you are learning about a subject. The fact is, Bell's Theorem has attracted the interest of many professional physicists. Over 1000 papers are written about it annually, many involving complex experiments as well.

 

[0xDEAD BEEF]

I am totaly sorry about "Either i am totaly stupid or something is very wrong here!". It seems i have "missed" Ballmer's peak!
I am really open minded so i allways tend to disagree. This is how i work! I will provide my proof by writing experimental programm so you can see what i mean!
Please be patient!
Beef

 

[Cthugha]

HEY - but we have FORGOTEN about another rule! There allways are two different pairs because of nature of photons!
(next post)

You will notice that this "easy" explanation will fail as soon as you consider putting polarizers in at arbitrary angles. There is a difference between what you would expect if there was a predefined value of the polarization as compared to having none for testing several combinations of polarizer settings.

I will provide my proof by writing experimental programm so you can see what i mean!

One thing to consider beforehand, as it might save you some time. It is easy to construct a classical HV explanation for some polarizer setting matching the experimental results. However, it is impossible to do the same when trying to match the experimental results using the same initial state, but many different polarizer settings. But you will soon find out yourself, which is a good way to learn stuff.

 

[0xDEAD BEEF]

BTW - before i go on with program - can i assume that A B and C were ment 0 +30 and -30 measurements?
Beef

 

[JesseM]

So you say - when they picked different boxes, they found out that they only got same fruits 1/4 of time? But of course! Because it is a rule that same boxes have same card on them! BUT also it is a rule, that two boxes have different card on them!

If the boxes on each card were printed with different fruits hidden behind them, then there would be a nonzero probability that Alice and Bob could pick the same box but get different results. But as I said at the beginning of the example, that never happens:

When we repeat this many times, we find that whenever they both pick the same box to scratch, they always get the same result--if Bob scratches box A and finds a cherry, and Alice scratches box A on her card, she's guaranteed to find a cherry too.

The point is that if we assume each box had a pre-determined fruit behind it (and that the machine printing each pair of cards didn't know in advance whether Alice and Bob would choose to scratch the same box or different boxes), then these two observations are inconsistent: 1) on the trials where they randomly choose to scratch the same box, they always see the same fruit, and 2) if they randomly choose different boxes (equal probability of each one), then they only see the same fruit on 1/4 of the trials. 1) or 2) could be true individually, but the "pre-determined fruit" theory cannot possibly explain how both could be true simultaneously.

 

[DrChinese]

BTW - before i go on with program - can i assume that A B and C were ment 0 +30 and -30 measurements?
Beef

Sure, those are 3 good angle settings to use. Don't forget there are other requirements too. Such as same answer for identical settings at ANY angle if the pair is polarization entangled.

So you should have Entangled State statistics for polarization entangled pairs (cos^2 rule) and Product State statistics for non-polarization entangled pairs (entangled pairs where the polarization is known). This second group may not seem possible, but each Type I PDC crystal actually produces this second group (Product State). You get the first group by combining the outputs of 2 Type I crystals oriented 90 degrees apart.

Now, using your logic, you should not be able to combine known output streams - with their predetermined and known values which never exceed 75% matching (averaged) - and get something that exhibits qualitatively different behavior. That being 100% matching. That is because superpositions do not follow ordinary rules. So I am just warning you, there are a lot of hoops to jump through and you have not fulfilled any yet.

 

[DrChinese]

I will provide my proof by writing experimental programm so you can see what i mean!

You can just describe what you are doing rather than writing a program. I doubt anyone is going to literally walk through the code with you. Although JesseM might.

There are teams out there that have attempted such programs and I have worked with the code of the foremost team in that area (in my opinion). They have needed to go outside of the Bell Theorem to find an angle of attack. Specifically: exploiting the fair sampling assumption. So again, I urge you to learn more before you come to firm conclusion.

You seem to be operating in reverse in that you form an opinion prior to obtaining suitable information. And then you defend your entrenched position. That is NOT being open minded!

 

[0xDEAD BEEF]

Ok - about program - it actually would be very simple. It would generate those ABC random pairs (same) and give them to Bob and Alice. Bob and Alice would then pick random and different "axis" to compare and come to conclusion, that error rate is 50%.

On second scenario same program would again generate pairs of ABC and give to both Bob and Alice, but this time program would follow rule so that at 75% of all cases B would match A and another rule that in 25% of cases C would match A (and in other cases it wont). Second run would show very different results and we would see them match with predicted by experiment. BECAUSE C and B are dependent on A, not randomly chosen! (or vice versa).

How i see this is - let's assume we got statue of rectangular cuboid (matchbox). Actually - this statue could also be a cube.

Lets have two observers at same distance but at different angles. We ask them question - what does it look like more - matchbox or cube? The further (angle) one observer moves from another, the more different figure he "might" observe. But still - both observations (especially if at angle 45%) would only complement each other, not "somehow" change statue it self.

So - where is the catch?Beef

 

[DevilsAvocado]

So - where is the catch?

DrChinese & JesseM are right. You have probably missed something crucial in EPR-Bell.

This is nothing to be 'upset' or 'ashamed' of; I did the exactly same thing, when I first heard about this paradox – "Haha! They are missing the obvious! I can solve this easily!"

But I was dead wrong (of course )...


As novice it’s easy to forget these crucial facts:

• The two polarizers at Alice and Bob are set independently and randomly.
  
  
• The two polarizers at Alice and Bob are separated spatially with no possibility to communicate the settings of the polarizers (at the speed of light between Alice and Bob).
  
  
• Consequently - nothing that happens at Alice can affect the outcome at Bob, and vice versa.

If you accept these three points, then it’s very hard to refute this:

When both polarizers are set to 0º, we will get 0% discordance.

Next we set first polarizer at +30º, and the second polarizer at 0º:

The discordance is 25%, according to QM and experiments.

Next we set first polarizer to 0º, and the second polarizer to -30º:

This discordance will also naturally be 25%.

Now let’s ask ourselves:

– What will the discordance be if we set the polarizers to +30º and -30º?​

If we assume a Local Reality, that NOTHING we do to one polarizer can affect the outcome of the other polarizer, we can formulate this simple Bell Inequality:

N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°)​

The symbol N represents the number of discordance (mismatches).

(The "is less than or equal to" sign is just to show that there could be compensating changes where a mismatch is converted to a match.)

We can make this simple Bell Inequality even simpler:

50% = 25% + 25%​

This is the obvious Local Realistic assumption.

But this is wrong! According to QM and physical experiments we will now get 75% discordance!

sin^2(60º) = 75%​

Thus John Bell has demonstrated by the means of very brilliant and simple tools that our natural assumption about a Local Reality is by over 25% incompatible with the predictions of Quantum Mechanics and physical experiments.
​

To learn more, check out http://www.drchinese.com/Bells_Theorem.htm" and these:

• http://en.wikipedia.org/wiki/EPR_paradox"
  
• http://en.wikipedia.org/wiki/Bell%27s_theorem"
  
• http://en.wikipedia.org/wiki/Bell_test_experiments"
  
• http://plato.stanford.edu/entries/bell-theorem/"
  
• http://plato.stanford.edu/entries/qt-epr/"
  
• http://www.iep.utm.edu/epr/"

If you do get some spare time, you can always check out this thread on PF; https://www.physicsforums.com/showthread.php?t=395509", to realize that most have probably already been said in the 1,500 replies and +58,000 views!


Good luck!

 

[0xDEAD BEEF]

No! I disagree!
Setting polarizers at angle -30% and +30% is same as setting polarizers at angle 0 and 60! But setting polarizers at 0 and 60% gives same result as setting at -30% and 0 (reverse sign).

Let look at same example, but take different angles - say - -45 and + 45. This will give 100% error (what actually means, that we receive 100% hit only reverse sign). Same as 0 and 90!

From the other perspective (this wrong one) 45 and 45 gave 50% error which should end up having same 50% error (50% error -> total random and total random x2 is still total random).

This explanation is against logic (because you operated with absolute values, whilst relation between measurements is clearly relative)
Beef

 

[DevilsAvocado]

No! I disagree!

Hehe, relax...

Next advice: Think, at least, twice before you are certain that you have discovered something that thousands of professors missed completely.

Setting polarizers at angle -30% and +30% is same as setting polarizers at angle 0 and 60!

Correct:
sin^2(0 + 60) = 75%
sin^2(30 + 30) = 75%

But setting polarizers at 0 and 60% gives same result as setting at -30% and 0 (reverse sign).

Wrong:
sin^2(0 + 60) = 75%
sin^2(-30 + 0) = 25%

I will not get into 45º or "Boxes" or "Doctors in Africa", or anything else. The example I gave you is 100% sufficient, if you want to understand what EPR-Bell is all about (in fact John Bell himself used this example when explaining EPRB to the public).

 

[0xDEAD BEEF]

Wrong:
sin^2(0 + 60) = 75%
sin^2(-30 + 0) = 25%

I will not get into 45º or "Boxes" or "Doctors in Africa", or anything else. The example I gave you is 100% sufficient, if you want to understand what EPR-Bell is all about (in fact John Bell himself used this example when explaining EPRB to the public).

Hmm... ok - maybe (and i really mean maybe) i start to see your point. Just can we clarify on what exactly this "match" means?
So - let's say Alise has her detector at 0 and Bob at 90. Let's assume, that Alice receives following sequence -
-+--++-

So - does 0 match means, that Bob received -
+-++--+

or does it means, that bob received totally unrelated (random) data?

Beef

 

[DevilsAvocado]

So - does 0 match means, that Bob received -
+-++--+

or does it means, that bob received totally unrelated (random) data?

Beef

With the risk of complicating things, the outcome at Alice & Bob is always 100% random. This means for example that it’s impossible to use EPRB to send information faster than the speed of light.

There are two 'exceptions' to this. When the relative angle between Alice & Bob is 0º or 180º we get so called "perfect correlation", which is "always same" or "always different", depending on angle and type of experimental setup.

But this in not extremely important, Alice & Bob will always see "random noise" at their ends. It’s only later, when the two measurements is compared and analyzed, that the pattern of correlation between Alice & Bob is revealed.


P.S. I sort of can 'see' what goes on in your head right now, because I’ve been there myself... It’s very easy to get blinded by the numbers and everything. Forget that. The only thing you need to focus on is this fact in red:

sin^2(30 + 30) = 75%​

This is the core. There is no "normal way" to put a plus sign between the polarizers at Alice & Bob.

They have absolutely NO idea at what angle "the other" polarizer will stop, and hence it’s impossible to do any "collective addition" to calculate the relative angel between the two. All this is done AFTER the whole experiment is completed.

 

[0xDEAD BEEF]

What is 75% mismatch?
Say - i got 8 +, the 75% mismatch is 6- and 2+? This more likely looks like 25% mismatch and inverse sign).

 

[DevilsAvocado]

What is 75% mismatch?

Mismatch/Discordance: Alice <> Bob
Match/Accordance: Alice = Bob

75% Mismatch/Discordance:

Alice
0000 0000

Bob
1111 1100

(This outcome is NOT fixed, it can be any sequence, as long as six of eight are different.)

 

[0xDEAD BEEF]

Good! So 100% mismatch is equal to exactly opposite data? So i would say, that 100% mismatch is sames as 100% match with reverse sign?
For example - Bob 0%, Alice 90%
Bob received: --++-++-

Then i can assume, that Alice received ++--+--+
?

Beefs

 

[DevilsAvocado]

Good! So 100% mismatch is equal to exactly opposite data?

Correct. Yes/No, +/-, or 1/0, all the way = 100% mismatch.

So i would say, that 100% mismatch is sames as 100% match with reverse sign?

Depends... if you reverse sign on only one (Alice or Bob) then this is correct. Reversed sign on both, you still got 100% mismatch...

Then i can assume, that Alice received ++--+--+
?

Wrong. You cannot assume anything at your end. You DON’T KNOW that the relative angle is 90º. It’s only AFTERWARDS when you get both data, that this becomes clear, but then you already know what Alice got...

 

[0xDEAD BEEF]

This formula is wrong.
N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°) (in my opinion of course.. ;) )

Ok - let's put it this way - if we would have non-related data. Random binary numbers. Then we could apply "30% polarization filter" to that data once and get 25% corrupted data. Then apply same filter again and get 50% (or less) corrupted data (compared to original). Btw 50% corrupted data actually is total random.

Then ok - this is how you use logic. This is how errors can be summed together.

Now - what is happening here is whole different story. I don't event dare to call that mismatch an error, because it is not. Either i still don't see the big point here, but - what i see is logic being used incorrectly. What i see from measurements is just [nothing special] (citation from Atis Slakters ) at all.

If i would use this logic, i could make another "Bells inequity"
N(+45°, -45°) ≤ N(+45°, 0°) + N(0°, -45°)

50% + 50% = 50% (you don't get right from two wrongs).! But this is wrong! According to QM and physical experiments we will now get 100% discordance!
sin^2(90º) = 100%But please let me remind you, that 100% discordance (just as we just agreed) actually is 100% ordnance!

So what i see is logic being used incorrectly. Well - but must likely I am again wrong and don't see the big picture here! :(
Beef

 

[DevilsAvocado]

This formula is wrong.
N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°) (in my opinion of course.. ;) )

Hehe, well you have to send (physicist heaven) the complaint to PhD John Stewart Bell, a specialist in nuclear physics and quantum field theory, that he doesn’t know how to calculate simple addition...

So what i see is logic being used incorrectly. Well - but must likely I am again wrong and don't see the big picture here! :(

You need to read more.

As I said, there are 'exceptions'. To go one step deeper, the 'exceptions' are angles 0, 45, 90, 135, 180, 225, 270, 315, 360.

This will not destroy Bell's theorem in any way, in fact the genius of Bell was go 'beyond' these angles. It is very doable to construct a LHV-model that works just fine (see LHVT below), if you only use the angles above. This was clear many years ago, and is not a "contemporary personal breakthrough"...

 

[0xDEAD BEEF]

Then just to make clear - if i would replace twin-photon generator by simple photon generator (any laser), and add polarization filters on both sides, so both photons have same polarization and then repeat same example randomly changing both polarization filter orientation and calcium crystal direction, i would get these linear results, not cos function?
I think, this experiment should be more than easy to accomplish even in poorly equiped lab. HEY- maybe this experiment has allready been produced??
Beef

 

[DrChinese]

If i would use this logic, i could make another "Bells inequity"

[1] N(+45°, -45°) ≤ N(+45°, 0°) + N(0°, -45°)

50% + 50% = 50% (you don't get right from two wrongs).! But this is wrong! According to QM and physical experiments we will now get 100% discordance!
sin^2(90º) = 100%

You have something wrong in your perspective here. The first formula [1] is classically "correct" and works just fine in some cases. It evaluates to:

100% ≤ 50% + 50%

So no problem. Works like a charm. That is because Bell's Theorem does not show violations at ALL angle combinations - as Avocado points out. This is one in which the "classical" rules works. But it obviously does NOT work with -30, 0, 30 degrees because you have:

75% ≤ 25% + 25%

Which is the violation Bell shows us, and disproves the classical reasoning.

 

[zonde]

This formula is wrong.
N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°) (in my opinion of course.. ;) )

This formula is correct.

Say we take four pairs of entangled photons.
1A / 1B
2A / 2B
3A / 3B
4A / 4B
Alice performs measurement at some angle a, Bob performs measurement at some angle b.
The angle a and b are chosen so that we get perfectly correlated result, say.
1A=0 / 1B=0
2A=0 / 2B=0
3A=1 / 3B=1
4A=0 / 4B=0

Now Alice performs measurement at angle a+30°, Bob performs measurement at angle b.
So to get 25% match with Bob you can change only one measurement for Alice.
1A=1 / 1B=0
2A=0 / 2B=0
3A=1 / 3B=1
4A=0 / 4B=0

Now Alice performs measurement at angle a, Bob performs measurement at angle b-30°.
To get 25% match with Alice you can change only one measurement for Bob.
1A=0 / 1B=0
2A=0 / 2B=1
3A=1 / 3B=1
4A=0 / 4B=0

And now Alice performs measurement at angle a+30°, Bob performs measurement at angle b-30°.
1A=1 / 1B=0
2A=0 / 2B=1
3A=1 / 3B=1
4A=0 / 4B=0
And minimum we get is 50% match because definitely two pairs are left unchanged.

 

[DrChinese]

Then just to make clear - if i would replace twin-photon generator by simple photon generator (any laser), and add polarization filters on both sides, so both photons have same polarization and then repeat same example randomly changing both polarization filter orientation and calcium crystal direction, i would get these linear results, not cos function?

No, you will NOT get those results. The graph Avocado presents is the BEST CASE that a Local Realistic Theory can yield in the sense that it is as close to the Quantum Mechanical predictions as it gets. That is not what actually occurs in an experiment, because the best case is merely hypothetical for a reality that does not occur in our universe (but which would still follow classical thinking).

 

[DevilsAvocado]

HEY- maybe this experiment has allready been produced??

Most probably, most probably... at least in theory in some genius brain...

You should know that spontaneous parametric down-conversion in BBO crystals is not a very effective process. Only one out of 10^6 photons converts into two entangled photons, one in a million.

This means that most photons that hit the detectors are "dummies". They don’t show any sign of QM correlations. I guess that this is a parallel to your "laser experiment"...

 

[DrChinese]

...

And now Alice performs measurement at angle a+30°, Bob performs measurement at angle b-30°.
1A=1 / 1B=0
2A=0 / 2B=1
3A=1 / 3B=1
4A=0 / 4B=0
And minimum we get is 50% match because definitely two pairs are left unchanged.

With this nice example, zonde is showing you what you would expect using classical/Local Realistic thinking. What you actually get, in an experiment, is something like:

1A=1 / 1B=0
2A=0 / 2B=1
3A=1 / 3B=0
4A=0 / 4B=0

So we actually get 25% match, when the minimum expected was 50%. So our assumption is wrong. Which is what Bell said.

 

[0xDEAD BEEF]

This means that most photons that hit the detectors are "dummies". They don’t show any sign of QM correlations. I guess that this is a parallel to your "laser experiment"...

Not exactly - there is no polarization filters between them and crystals! ;)
Beef
P.S. i still totaly disagree and do not accept this idea, but i guess that is because of my incomplete knowledge!

BTW - so say i do conduct this experiment using normal light polarized using polarization fitlers (two polarizations filters polarizing light) - what results would i get?

 

[DevilsAvocado]

Not exactly - there is no polarization filters between them and crystals! ;)
Beef
P.S. i still totaly disagree and do not accept this idea, but i guess that is because of my incomplete knowledge!

Well... some things you say... do make sense… (sorry bad joke )

BTW - so say i do conduct this experiment using normal light polarized using polarization fitlers (two polarizations filters polarizing light) - what results would i get?

Not that great I would say. Let’s assume we have the Source (S), Polarizer1 (P1), Polarizer2 (P2), and the Measuring apparatus (M), setup like this:

S----->-----P1----->-----P2----->-----M

Unpolarized normal light will go thru P1. Independent of the angle of P1, 50% of the light will pass thru. Let’s say we set P1 to 90º. Now P2 will have to 'relate' to the angle of P1. If P2 is set to 0º, no light will pass. If P2 is set to 45º, 25% of the (original) light will pass. If P2 is set to 90º, 50 % of the (original) light will pass.

You can play with different settings in this http://www.lon-capa.org/~mmp/kap24/polarizers/Polarizer.htm" , but I don’t think it will help you design a LHVT.

 

[zonde]

You should know that spontaneous parametric down-conversion in BBO crystals is not a very effective process. Only one out of 10^6 photons converts into two entangled photons, one in a million.

This means that most photons that hit the detectors are "dummies". They don’t show any sign of QM correlations. I guess that this is a parallel to your "laser experiment"...

There are not so much dummies. Pump photons are separated from downconverted photons (they usually have slightly different direction) and they do not arrive at detectors.
But if pump photon is downconverted there are always two downconverted photons leaving the source. Of course you can loose some along the way.
Anyways it's possible to make setup where more than 50% of detections at one detector are paired with detections at other detector (but not vice versa). Actually for me it's clearest demonstration that photons are particles (at macro scale).

 

[0xDEAD BEEF]

So I think is start to see the problem here!
All this proof is based on this formula output

N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°)

not matching measurements, right?

And this N function is function, which describes error (mismatch?). Right?

So - can i remove "two parameters" from this function and convert to one, since "error" is always calculated comparing output at Alise's detector to output at Bob's detector and absolute angle does not play role here, since polarization of photons is not known from very beginning?

So, should this also be true?
N(60°) ≤ N(30°) + N(30°)

Beef
EDIT: BTW - what is "two-channel polariser" and where do i get one! :)
EDIT2: two-channel polariser is same thing as "Wollaston prism" ?

 

[DevilsAvocado]

So I think is start to see the problem here!
All this proof is based on this formula output

N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°)

not matching measurements, right?

YES!

Not only measurements, it does not match the theoretical predictions of Quantum Mechanics (which is the most precise theory we have).

And this N function is function, which describes error (mismatch?). Right?

YES!

So, should this also be true?
N(60°) ≤ N(30°) + N(30°)

YES!

We could 'simplify' this even more and say:

50% = 25% + 25%

And more, by dividing by 25:

2 = 1 + 1

Or reversed, that works even for kids!

1 + 1 = 2

This is what we expect. This is the how "the normal world" should work. But, then comes the 'weird' QM-world and tell us that – This is how it works!

1 + 1 = 3

! !

EDIT: BTW - what is "two-channel polariser" and where do i get one! :)
EDIT2: two-channel polariser is same thing as "Wollaston prism" ?

This video explains the basics in EPR-Bell experiments:

https://www.youtube.com/watch?v=<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/c8J0SNAOXBg&hl=en_US&fs=1&rel=0&color1=0x006699&color2=0x54abd6"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/c8J0SNAOXBg&hl=en_US&fs=1&rel=0&color1=0x006699&color2=0x54abd6" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

And here you find more info on the equipment: http://www.didaktik.physik.uni-erlangen.de/quantumlab/english/"

And if you really going to have a experimental shot at this, you should read this:

http://arxiv.org/abs/quant-ph/0205171"

 

[DevilsAvocado]

Hey DrC! Nice pink! (me want! )

 

[DevilsAvocado]

Anyways it's possible to make setup where more than 50% of detections at one detector are paired with detections at other detector (but not vice versa). Actually for me it's clearest demonstration that photons are particles (at macro scale).

Thanks for clarifying.

Well, some say it’s particles, and some say wave/particles, and some only wave + a "click".

I have absolutely no idea what’s really true... (and I guess I’m not alone )

 

[0xDEAD BEEF]

So i wrote program which generates photons with random orientation and throws them at detectors. Now i got linear output comparing detectorA to detectorB. I wrote my detectors so, that they fire, if photon angle +- 45 degrees matches with detector angle. Is this correct detector setting?

So - if we assume, that measurement of one photon changes orientation of other... Why do we get random data output at Alisa's or Bob's detector? Why is not it so, that one detector returns more + than - or vice versa (thus - if detector has affected orientation of photon should not this detector fire more often, since photon's direction is changed to "suite" that(first) detector) ?

Beef

 

[DrChinese]

So i wrote program which generates photons with random orientation and throws them at detectors. Now i got linear output comparing detectorA to detectorB. I wrote my detectors so, that they fire, if photon angle +- 45 degrees matches with detector angle. Is this correct detector setting?

So - if we assume, that measurement of one photon changes orientation of other... Why do we get random data output at Alisa's or Bob's detector? Why is not it so, that one detector returns more + than - or vice versa (thus - if detector has affected orientation of photon should not this detector fire more often, since photon's direction is changed to "suite" that(first) detector) ?

Beef

First, 45 degree angles usually won't show much relative to Bell's Theorem. Second, it is very difficult to follow some of your questions - so I will try as best I can.

The general rule for a polarization entangled photon pair is that a measurement on Alice acts "AS IF" it causes a matching change to Bob. (Note the AS IF because no one is actually saying that can be proven. It is one of several possibilities. However it is useful for the rule, which is correct.) So if you measure Alice at 45 degrees, Bob will act as if he is likewise polarized at 45 degrees. Stats can then be calculated for any subsequent measurement on Bob (or Alice for that matter).

An important note because I think this can be confusing if it is not explicitly pointed out: Entangled photon pairs can be created either I) so Alice and Bob have the same polarization; or II) Alice and Bob have orientations 90 degrees apart. This is controlled by the choice of PDC crystals (called Type I or Type II).

Finally, any sequence of Alice will be random + and -, more or less equal, and Bob will be random too. Depending on the relative angle theta between then, their matches will show a pattern or not. Cos^2(theta) is the rule for Type I, Sin^2(theta) is for Type II. I always provide examples as Type I because it is easier to discuss.

 

[0xDEAD BEEF]

So how i now see this is that if instead of twin photons i would use simple photons with same polarization, then this same experiment would produce linear graph, not cos. Right?

So this would mean, that measurement on Alisa's photon has affected Bob's photon to be the same, BUT Alisa's photon somehow matches betters Alisa's detector? So we should see more + photons than - (or vice versa) photons at Alisa's detector?

Edit: or does this measurement says, that now that photons (both) know their polarization for Alisa's detector, they will respond with same value, but since they don't know polarization value for Bob's settings, they have not made that up yet so when Bob measures his photon, his photon wonders what value should it return to Bob, since Alisa did not measure exactly same "setting" so Bob's photon comes up with some new random value? :)

Edit2: And if so, should not those two photons have decided their polarization values earlier already (traveling through space and hitting various magnetic/electric fields or dust) ?

Beef

 

[DevilsAvocado]

I wrote my detectors so, that they fire, if photon angle +- 45 degrees matches with detector angle. Is this correct detector setting?

I’m not sure what you’re aiming at... do you mean the polarizing beam splitter?

This is 'just' to be able to measure all arriving photons (both Up/Down, +/-, 1/0, Yes/No), to get better 'precision'...

Why do we get random data output at Alisa's or Bob's detector? Why is not it so, that one detector returns more + than - or vice versa

Try to think of it like this: Basically at each end Alice & Bob receive unpolarized light that they run thru a polarizer. As you can test by yourself in the http://www.lon-capa.org/~mmp/kap24/polarizers/Polarizer.htm" , no matter what angle you set there will always be a 50% chance for the light (photon) to go thru, when the light is unpolarized.

To make more precise measurements, we take care of both "thru" & "stopped" by a polarizing beam splitter. This means there is always 50/50 chance for the photon to be detected at each detector after the beam splitter.

The EPRB 'mystery' lays in the correlations in the sequence of photons between Alice & Bob.

For example, let’s say we have a relative angle of 60º between Alice & Bob, meaning there’s a 75% mismatch. When counting 8 photon pairs, we could get this:

Alice: 0000 0000
Bob..: 1111 1100

But, more probably we will see something like this:

Alice: 0101 0101
Bob..: 1010 0011

Get it?

 

[DrChinese]

1. So how i now see this is that if instead of twin photons i would use simple photons with same polarization, then this same experiment would produce linear graph, not cos. Right?

2. So this would mean, that measurement on Alisa's photon has affected Bob's photon to be the same, BUT Alisa's photon somehow matches betters Alisa's detector? So we should see more + photons than - (or vice versa) photons at Alisa's detector?

Edit: or does this measurement says, that now that photons (both) know their polarization for Alisa's detector, they will respond with same value, but since they don't know polarization value for Bob's settings, they have not made that up yet so when Bob measures his photon, his photon wonders what value should it return to Bob, since Alisa did not measure exactly same "setting" so Bob's photon comes up with some new random value? :)

3. Edit2: And if so, should not those two photons have decided their polarization values earlier already (traveling through space and hitting various magnetic/electric fields or dust) ?

Beef

1. No, it is a completely different formula that involves 3 variables but follows classical rules (Malus).

2. I cannot follow your question. I assume English is not your native language so if you could rephrase that would be helpful. There is no reason you would see more + than - anywhere, not sure what your thinking is on that but it is not correct.

3. Free space fields generally will not affect photon polarization in any way. Many times the effects cancel out. Now, if you go through an optical device such as a polarizing beam splitter or a wave plate you can see effects.

 

[0xDEAD BEEF]

Sorry! I don't get it! :)
I would really apreciate, if you could answer this question-

->>
So this would mean, that measurement on Alisa's photon has affected Bob's photon to be the same, BUT Alisa's photon somehow matches betters Alisa's detector? So we should see more + photons than - (or vice versa) photons at Alisa's detector?

Edit: or does this measurement says, that now that photons (both) know their polarization for Alisa's detector, they will respond with same value, but since they don't know polarization value for Bob's settings, they have not made that up yet so when Bob measures his photon, his photon wonders what value should it return to Bob, since Alisa did not measure exactly same "setting" so Bob's photon comes up with some new random value? :)
<<-

What i mean is - where does it start to make difference between twin-photons and photons with same polarization. How would this change results of experiment. Let's say - i have black-box device which creates "twin-photons", which actualy are not twin photons, but simply photons with same polarization. Where would this change output of these measurements.

--
The big idea behind this theory/experiment is, that polarization of these photons becomes "known" only as they get measured (pass thru polarization filter (Wollaston prism?)).
Am i right?

Beef
P.S. english is not my native language, sorry.

 

[zonde]

So how i now see this is that if instead of twin photons i would use simple photons with same polarization, then this same experiment would produce linear graph, not cos. Right?

No, it would produce cos^2(a)*cos^2(b) where a and b are angle between polarization axis of photons and polarization axis of respective polarizer.

In case of entanglement you get something like:
cos^2(a)*cos^2(b)+sin^2(a)*sin^2(b)+1/2*sin2a*sin2b=cos^2(a-b)
this third term (1/2*sin2a*sin2b) is called interference term and it's the one that complicates things.

 

[0xDEAD BEEF]

zonde! regarding

No, it would produce cos^2(a)*cos^2(b) where a and b are angle between polarization axis of photons and polarization axis of respective polarizer.

as i said, i would use black-box, so, whatever "polarization axis of respective polarizer" is, i can no know that! So - what output would i get?
Beef

 

[DevilsAvocado]

What i mean is - where does it start to make difference between twin-photons and photons with same polarization. How would this change results of experiment. Let's say - i have black-box device which creates "twin-photons", which actualy are not twin photons, but simply photons with same polarization. Where would this change output of these measurements.

--
The big idea behind this theory/experiment is, that polarization of these photons becomes "known" only as they get measured (pass thru polarization filter (Wollaston prism?)).
Am i right?

Well, now we are talking!

First, two photons with the same "pre-polarization" will not do any good in EPRB = dead end. Just check the math.

The second part is touching the real juicy stuff in EPRB! This almost makes me throw up! And I know that it 'troubled' John Bell as well...

Who decide, Alice or Bob??

According to Einstein’s Special Relativity, BOTH DECIDE! In different frame of reference!

It doesn’t make sense, right? Only one can decide, anything else is just pure stupidity, right?

But this is the way it is, in current science, and to me this is more shocking than any locality or reality... the future is probably going to show us some real interesting "features" of nature...