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Why is superdeterminism not the universally accepted explanation of nonlocality?

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lugita15
#145
Feb29-12, 01:55 PM
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Quote Quote by ThomasT View Post
You didn't, afaik. But you seem to be defending the notion that superdeterminism can explain BI violations.
All I'm saying is that Bell's theorem as such does not necessarily rule out superdeterminism, but it definitely rules out all other forms of local realism.
As for your 12-step recounting of Bell's argument, the conclusion that the correlation between the angular difference of the crossed polarizers and the rate of coincidental detection should be linear given the assumption of local determinism is wrong.
If my conclusion is wrong, one of my steps must be wrong. Which one is it?
ThomasT
#146
Feb29-12, 10:29 PM
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Quote Quote by lugita15 View Post
All I'm saying is that Bell's theorem as such does not necessarily rule out superdeterminism, but it definitely rules out all other forms of local realism.
I basically agree with this ... with the qualifier that what Bell's theorem definitively rules out are Bell-type LR models of quantum entanglement. Whether non-Bell-type LR models can be definitively ruled out is still an open question, afaik. (Because, it's still an open question as to whether certain non-Bell-type LR models are actually LR models.)

Quote Quote by lugita15 View Post
If my conclusion is wrong, one of my steps must be wrong. Which one is it?
You're saying that the local realist would expect a linear correlation between θ and coincidental detection. Why would the local realist expect that?

My point is that if the local realist is aware of the historically documented characteristic behavior of light, then he wouldn't expect, in a local deterministic world, a linear correlation between the angular difference of the crossed polarizers and the rate of coincidental detection. He would, rather, expect a nonlinear correlation ... something approximating cos2θ.

The fact that Bell inequalities are, more or less, based on formal constraints which require the light in Bell tests to behave in an uncharacteristic way suggests that there's something in those constraints which is not corresponding to Bell test preparation and associated data processing. But not necessarily that nature is nonlocal.
lugita15
#147
Feb29-12, 10:34 PM
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Quote Quote by ThomasT View Post
You're saying that the local realist would expect a linear correlation between θ and coincidental detection. Why would the local realist expect that?
To repeat, the fact that local realism implies a linear correlation is NOT some arbitrary assumption or constraint we place on local realist theories. It is the conclusion of a careful argument, and if you're claiming the conclusion is wrong then there must be something wrong with this argument.
ThomasT
#148
Feb29-12, 10:55 PM
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Quote Quote by lugita15 View Post
To repeat, the fact that local realism implies a linear correlation is NOT some arbitrary assumption or constraint we place on local realist theories. It is the conclusion of a careful argument, and if you're claiming the conclusion is wrong then there must be something wrong with this argument.
Why does the argument assume that the correlation between θ and rate of coincidental detection should be linear?
lugita15
#149
Feb29-12, 10:58 PM
P: 1,583
Quote Quote by ThomasT View Post
Why does the argument assume that the correlation between θ and rate of coincidental detection should be linear?
Argh! ThomasT, I told you, the argument does not assume it, it proves it.
ThomasT
#150
Feb29-12, 11:09 PM
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Quote Quote by lugita15 View Post
Argh! ThomasT, I told you, the argument does not assume it, it proves it.
I didn't get that. How does it prove it?
zonde
#151
Feb29-12, 11:25 PM
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Quote Quote by billschnieder View Post
Bah! I had hoped you will have seen problem the so called "DrChinese challenge" by now. You keep saying:

- give me a dataset with values for simultaneous polarization outcomes at 0, 120 and 240 degrees.

Don't you yet understand that "dataset with simultaneous outcomes" implies an experiment is being performed. Previously I asked you to describe the experiment and I will give you the dataset but you never described the experiment because you can not and nobody can because THERE CAN NEVER BE AN EXPERIMENT WHICH SIMULTANEOUSLY MEASURES TWO PHOTONS AT 3 ANGLES (yes I'm shouting this time).

Therefore failure of anybody to provide your purported dataset is not due to anything other than the fact that the request is nonsensical.
Under local realism cloning of entangled pair is completely valid operation. From that follows that "DrChinese challenge" is applicable to LR models.

While I am proponent of local realism I side with DrChinese in this. Have to say that you can have constructive discussions with DrChinese and I am grateful to him as discussions with him have shaped a lot my own understanding about entanglement problem.
zonde
#152
Feb29-12, 11:33 PM
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Quote Quote by f95toli View Post
I don't normally get involved in these discussions, because ultimately I don't think they are very interesting.
However, I thought I'd add my (usual) comment about experimental QM.

Whereas nearly all "conceptual" (and many practical) experiments are done using light, there are lots of examples of QM experiments that do NOT involve light, angular momentum, polarization, photon detectors etc.

People have performed experiments that are formally exactly analogues to the early (optical) tests of Bell's inequalities. We will probably see the first demonstrations in my own field pretty soon (solid-state QIP, which has nothing to do with optics but the QM formalism is obviously the same)
Hence, any attempt to explain away Bell type experiments by saying that that results are due to the fact we do not understand a specific technical detail of Aspect's original experiments is ultimately futile.

Moreover, note also that we are nowadays often -in practical- terms more concerned about OTHER inequalities that for one reason or another are better to test experimentally. A good example are tests of Legget-type inequalities which can used to test whether or not QM is local.
Can you give one good reason why your position is not subject to confirmation bias?
zonde
#153
Feb29-12, 11:44 PM
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Quote Quote by lugita15 View Post
Argh! ThomasT, I told you, the argument does not assume it, it proves it.
I would like to see this. Hmm, my guess would be that you are assuming perfect (anti-)correlations for matching measurement settings.
lugita15
#154
Mar1-12, 12:16 AM
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Quote Quote by zonde View Post
I would like to see this. Hmm, my guess would be that you are assuming perfect (anti-)correlations for matching measurement settings.
You're right, I am assuming that. But that's a harmless assumption to make. Perfect correlations for matching measurement settings is a consequence of quantum mechanics, so surely if a local realist theory wanted to match the predictions of QM then it would have to have perfect correlations for matching measurement settings. I highly doubt this is what ThomasT is disputing.

(You can, of course, be the fringe type of local realist who has a theory making predictions contrary to QM, but who believes that the only reason the experiments have proven QM right is that they're subject to various flaws, loopholes, and systematic biases. But as Bell tests become more sophisticated, that becomes an increasingly untenable positon, arguably even more so than superdeterminism.)
lugita15
#155
Mar1-12, 12:50 AM
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Quote Quote by ThomasT View Post
I didn't get that. How does it prove it?
The whole point of the entire proof is to show that the correlation is linear, but if you want the step that directly leads to it, look at 11: "So 75% of the time, P(-30)=P(0), and 75% of the time P(0)=P(30), so there's no way that P(-30)≠P(30) 75% of the time." But this is pretty much an indisputable step, because it's just math, not physics: if A has a 25% chance of occurring, and B has a 25% chance of occurring, then the probability that at least one of them occurs is at most 50%. It's definitely not possible for A to have a 25% chance of occurring, B to have a 25% chance of occurrring, but a 75% chance that at least one of them occurs.

Presumably you don't disagree with the straightforward math of step 11, so if you reject the conclusion that local realism implies linear correlation you must reject one of the earlier steps.
ThomasT
#156
Mar1-12, 01:16 AM
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Quote Quote by lugita15 View Post
The whole point of the entire proof is to show that the correlation is linear, but if you want the step that directly leads to it, look at 11: "So 75% of the time, P(-30)=P(0), and 75% of the time P(0)=P(30), so there's no way that P(-30)≠P(30) 75% of the time." But this is pretty much an indisputable step, because it's just math, not physics: if A has a 25% chance of occurring, and B has a 25% chance of occurring, then the probability that at least one of them occurs is at most 50%. It's definitely not possible for A to have a 25% chance of occurring, B to have a 25% chance of occurrring, but a 75% chance that at least one of them occurs.

Presumably you don't disagree with the straightforward math of step 11, so if you reject the conclusion that local realism implies linear correlation you must reject one of the earlier steps.
I don't understand your notation. For example, what does this mean? "So 75% of the time, P(-30)=P(0), and 75% of the time P(0)=P(30), so there's no way that P(-30)≠P(30) 75% of the time." I'm assuming that P(-30) refers to the probability of coincidental detection while keeping the setting of the A polarizer vertical and offsetting B, to the left, 30 degrees. And that P(30) refers to the probability of coincidental detection while keeping the setting of A vertical and offsetting B, to the right, 30 degrees. If so, then what? I don't get what "75% of the time, P(-30)=P(0)" is supposed to mean. Or what "75% of the time P(0)=P(30)" is supposed to mean.

Do you just mean that the probability of coincidental detection at θ=30 degrees is .75?

I think that's what you mean, so lets go with that. But wait, where did that come from? The polarizers were actually set that way, and you noted the result? Right?

Ok, so we have a probability of coincidental detection at θ=30 of .75 .

Then we set A 30 degrees to the left and B 30 degrees to the right, so now we have a θ of 60 degrees.

So now do we do some runs to see what the rate of coincidental detection at θ=60 degrees is, or do we first assume something about what that rate should be? And if we assume something about what that rate should be, then what's that assumption based on?
lugita15
#157
Mar1-12, 01:18 AM
P: 1,583
ThomasT, I define P(θ) in step 2: "A local realist would say that the photon doesn't just randomly go through or not go through the detector oriented at an angle θ; he would say that each unpolarized photon has its own function P(θ) which is guiding it's behavior: it goes through if P(θ)=1 and it doesn't go through it P(θ)=0."

Let's get right to the heart of the matter. If P(-30)=P(0) and P(0)=P(30), then P(-30) must equal P(30). Thus if P(-30) does not equal P(30), either P(-30)≠P(0) or P(0)≠P(30) (or both). Since there is a 25% error rate whenever there is a thirty degree seperation, we know that the probabilities that P(-30)≠P(0) is 25%, and the probability that P(0)≠P(30) is 25%, and the probability that at least one of these two statements is true is at most 25%+25%=50%. This is not a physical assumption or constraint, it's just math. If event A happens 25% of the time and event B happens 25% of the time, then it's guaranteed that at least 50% of the time neither one of them occurs. If taxis are available in New York City a quarter of the time, and buses are available a quarter of the time, then you know that transportation is available at most 50% of the time. I hope you don't dispute this.
ThomasT
#158
Mar1-12, 02:27 AM
P: 1,414
Quote Quote by lugita15 View Post
Since there is a 25% error rate whenever there is a thirty degree seperation, we know that the probabilities that P(-30)≠P(0) is 25%, and the probability that P(0)≠P(30) is 25%, and the probability that at least one of these two statements is true is at most 25%+25%=50%.
That assumes that there's a linear correlation between θ and rate of coincidental detection. But the historically observed and documented behavior of light suggests otherwise. So, where did this assumption come from?
lugita15
#159
Mar1-12, 02:42 AM
P: 1,583
Quote Quote by ThomasT View Post
That assumes that there's a linear correlation between θ and rate of coincidental detection. But the historically observed and documented behavior of light suggests otherwise. So, where did this assumption come from?
In step 11 we're not making any assumptions about physics, we're just doing math. If the probability of A is 25% and the probability of B is 25%, then the probability of "A or B" is at most 50%, regardlesss of what A and B are and whether they have anything to do with each other. (Note that "A or B" means at least one of them is true.) That is just a simple mathematical fact. In this case, A is "P(-30)≠P(0)" and B is "P(0)≠P(30)".

As I said, once you've gotten down to step 11 there is no room for argument left, it's just math. If you want to dispute the reasoning you'll have to find an earlier step you disagree with.
Demystifier
#160
Mar1-12, 03:27 AM
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Lugita15, I would like to see your response to my post #127.
jadrian
#161
Mar1-12, 03:27 AM
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Quote Quote by jadrian View Post
By the way i think you should be focusing more on simply c and d which i presume are next to the measurement devices and thus are far apart so they are the "conspirators", because they causally effect the outcome of the measurements by bumping the measurement device into whatever angle. either way a and d or c and d doesnt matter which you consider to be conspiring. There should be nothing conspiratorial about particle d being able to affect particle c and therefore effect a because in the history of the universe, the 10^10^MILLION (who can say how many?) interactions that have taken place, through causality and info exchange, HAVE PREDETERMINED that particle d was going to effect c and therefore a. you say a and d seemingly have nothing to do with eachother. THEY HAVE EVERYTHING TO DO WITH EACHOTHER! Simple logical determinism would lead you to the conclusion that d had causal effects on perhaps everything in the universe which ultimately led to the causal outcome of the measurement of a. Not only that but particle d,d1,d2,d3 d infinity not only via cause-effect cause-effect cause-effect.....eventually caused c to affect the measurement device for a, but d, d1, d2..... caused the experimenters to make the experiment take place in the first place.

i dont believe faster than light info transfer will be an issue here as it is not an issue with normal entanglement, because info transfered at the speed of light will always beat instantaneous info transfer to the punch. Sending light in opposite directions i suspect would be solvable by relativity to give the same conclusion.

dont think of it not particles all knowing about eachother, think of it as historical interactions in the universe as spreading a virus to every particle in the entire universe.

its not that every particle knows everything about every other particle. it only knows what has happened to it in the past. but the addition of all current states of particles which are in their current state because of their continuous past history traced back in time will give you the full information in the universe, and having this information, you would be able to predict it. and if you could predict it, that would mean it must be deterministic as a whole. so although we cannot predict the future, and the future isnt predictable, que sera' sera'.
let me clarify this a little bit. the "conspiracy" is simply the result of the history of the causal interactions of ALL the stuff in the universe. the affect of d on a is not just a relationship between of d and a. it is a result of d and a being the part of the sum of everything in the universe. d and a alone would not be able to affect eachother if isolated from the history of all interactions in the universes past. it requires all the information in the universe to result in determinism. there is nothing super about it.

if determinism only is effective within lightcones, in which case if outside eachothers lightcones, a and d could not affect eachother just as future events cannot effect the past, as lightcones expand at the speed of light, if there were particle a that had not yet interacted with other particles d1 d2 d-infinity, (i stated before that this should be impossible under a causally governed universe) in this hypothetical case it would be not practically, but THEORETICALLY impossible to do such an experiment or have such nonlocal effects even without an experiment. also, along with photons a and b traveling in opposite directions, so too will plenty of other EFFECTUAL information be propagated to a and d from particles locally and causally effecting the photon source, so it would make a and d effectively the same as being locally deterministic. it would be determined tho in the universe that the lightcones would eventually expand to make a and d react causally therefore deterministically.
lugita15
#162
Mar1-12, 03:42 AM
P: 1,583
Quote Quote by Demystifier View Post
Lugita15, I would like to see your response to my post #127.
Oh, I agree wholeheartedly that all of the theories listed in your blog post are viable alternatives (with the exception of Joy Christian), and that they are each in one way or another local, and even that some of them are in one way or another realistic or deterministic. But I think the only alternative out of your list that deserves the appelation "local determinism" is superdeterminism, because it is the only when where the real future states of real particles in our 3-dimensional universe are determined by the real past states and real local interactions of real particlces (whew, I think I put enough qualifications). But yes, there are several viewpoints that someone like backwards causation where some pedant could make the argument that we have a local determinist theory.

Still, it's a worthwhile task to show that local realism (unless it's superdeterministic) using the conventional definiton cannot reproduce the predictions of quantum mechanics.


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