why is superdeterminism not the universally accepted explanation of nonlocality?


by jadrian
Tags: accepted, explanation, nonlocality, superdeterminism, universally
lugita15
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#271
Mar5-12, 07:01 PM
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Quote Quote by ThomasT View Post
The rate of individual detection doesn't vary with the measurement parameter, but the rate of coincidental detection does vary with the measurement parameter. So, what would you infer from this?
But there isn't some magical thing called "joint detection" or "coincidence detection". Rather, each experimenter just does individual detection of each photon, and records the results. We draw conclusions about the "rate of coincidental detection" AKA the correlation based on the results of individual detections. Since there is no such thing as coincidence detection, and correlation is nothing but correlation of individual detections, an analysis of entanglement cannot consist, even in principle, of anything other than asking what determines the results of individual detection.
Joncon
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#272
Mar5-12, 07:10 PM
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Quote Quote by ThomasT View Post
If you could phrase this a bit less anthropically, that would be helpful. Photons aren't people.
I agree, that's why I double-quoted "choose". Okay, to put it another way, what determines which function (individual/coincidental) is applied to the photons?

Quote Quote by ThomasT View Post
We're talking about different measurement parameters. Is it unreasonable to suppose that these different measurement parameters are measuring different underlying parameters?
But they're not different measurement parameters. Each photon has it's polarization measured. That's it.
ThomasT
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Mar5-12, 07:24 PM
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Quote Quote by lugita15 View Post
But there isn't some magical thing called "joint detection" or "coincidence detection".
Who said anything about magic? The term rate of coincidental detection refers to a statistical accumulation, and that statistical accumulation varies as the measurement parameter varies. The term rate of individual detection also refers to a statistical accumulation, and that statistical accumulation doesn't vary as the measurement parameter varies. I asked what you might infer from this fact.

Quote Quote by lugita15 View Post
Since there is no such thing as coincidence detection, and correlation is nothing but correlation of individual detections ....
Of course there's such a thing as coincidence detection. What do you think Bell tests are about? The term Bell correlations refers to correlations between θ, the angular difference between the separated polarizers, and the rate of coincidental detection.

Quote Quote by lugita15 View Post
... an analysis of entanglement cannot consist, even in principle, of anything other than asking what determines the results of individual detection.
I would guess that that's what a lot of people think. And therein lies much of the confusion surrounding the meaning of Bell's theorem.

Anyway, of course an analysis of entanglement can consist of something other than asking what determines the results of individual detection. It starts with recognizing that the rates of individual and coincidental detection are determined by different parameters.
ThomasT
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#274
Mar5-12, 07:30 PM
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Quote Quote by Joncon View Post
I agree, that's why I double-quoted "choose". Okay, to put it another way, what determines which function (individual/coincidental) is applied to the photons?
The measurement parameter.

Quote Quote by Joncon View Post
But they're not different measurement parameters.
Yes they are. The orientation of an individual polarizer is a different measurement parameter than the angular difference between two polarizer orientations.
lugita15
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Mar5-12, 07:37 PM
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Quote Quote by ThomasT View Post
Who said anything about magic? The term rate of coincidental detection refers to something, and that something varies as the measurement parameter varies. There's also something called rate of individual detection, and that something doesn't vary as the measurement parameter varies. I asked what you might infer from this fact.
But whatever these rates are, they do not arise full-grown from the head of Zeus, do they? They are calculated solely from the results of individual detections of photons. Thus the only thing that can affect these rates are those results. So explaining the "rate of coincidence detection" consists of another more and nothing less than explaining the results of individual detection.
Of course there's such a thing as coincidence detection. What do you think Bell tests are about? The term Bell correlations refers to correlations between θ, the angular difference between the separated polarizers, and the rate of coincidental detection.
There is no experimental procedure called "coincidence detection", so the term "rate of coincidence detection" is highly misleading. Coincidences aren't "detected" experimentally, they are a consequence of individual detections.
Anyway, of course an analysis of entanglement can consist of something other than asking what determines the results of individual detection. It starts with recognizing that the rates of individual and coincidental detection are determined by different parameters.
They are both entirely determined by the same thing, the results of individual detections; that is, whether photon A from pair N goes through the polarizer oriented at the angle θ, to which the answer is either yes or no. I don't know how you can possibly disagree with this.
Joncon
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Mar5-12, 07:49 PM
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Quote Quote by ThomasT View Post
Yes they are. The orientation of an individual polarizer is a different measurement parameter than the angular difference between two polarizer orientations.
But when photon A encounters polarizer A there's no such thing as "angular difference between two polarizer orientations". A (photon or polarizer) has no knowledge of what is happening at B.
ThomasT
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#277
Mar5-12, 08:00 PM
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@ Joncon and lugita15,

I think this is a case of "not seeing the forest for the trees". There are two different measurement contexts to consider. The results wrt which are determined by different parameters, both measurement and assumed underlying.

I'm going to take a time out now. Please reread what I've written. Think about it some more. And I'll get back to you in a few hours.
ThomasT
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#278
Mar5-12, 08:02 PM
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Quote Quote by Joncon View Post
But when photon A encounters polarizer A there's no such thing as "angular difference between two polarizer orientations".
Right, this is an individual measurement context. Do you think there's a difference between this measurement context and the one where coincidental detections are correlated with θ?
ThomasT
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#279
Mar5-12, 08:04 PM
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Quote Quote by lugita15 View Post
They are both entirely determined by the same thing ... I don't know how you can possibly disagree with this.
Read my most recent posts again. I'll get back to you.
ThomasT
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#280
Mar5-12, 08:53 PM
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Quote Quote by lugita15 View Post
There is no experimental procedure called "coincidence detection" ...
Sure there is. There's circuitry that matches detection attributes which operates according to calculations based on the photon emission source and the distance between the polarizers.

Quote Quote by lugita15 View Post
... so the term "rate of coincidence detection" is highly misleading. Coincidences aren't "detected" experimentally, they are a consequence of individual detections.
They're a consequence of matching individual detection attributes wrt calculated coincidence intervals.

Whether coincidental detections are counted 'on the fly' by circuitry built into the experimental design, or after the fact via time stamps, the fact is that the basic datum of entanglement setups (eg., Bell tests) is called coincidental detection, and the rate of coincidental detection varies as a function of θ, the angular difference between the polarizer settings.

So, given that the rate of individual detection doesn't vary as a function of polarizer setting, then what can you infer from this?

Quote Quote by lugita15 View Post
They are both entirely determined by the same thing ...
No. Incorrect inference. This doesn't follow from the known experimental results.
lugita15
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Mar5-12, 09:19 PM
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Quote Quote by ThomasT View Post
Sure there is. There's circuitry that matches detection attributes which operates according to calculations based on the photon emission source and the distance between the polarizers.
They're a consequence of matching individual detection attributes wrt calculated coincidence intervals.
But these are just contingent facts about experimental design. Consider an idealized experiment where one photon pair is sent out every hour by a source which is exactly at the midpoint between two polarizers, which catch every single photon with perfect accuracy. In that case all each experimenter has as far as data goes is a list of yes or no answers as to whether the photon went through the polarizer or not. There are no time stamps, distance measurements, coincidence intervals, or anything like that.
Whether coincidental detections are counted 'on the fly' by circuitry built into the experimental design, or after the fact via time stamps, the fact is that the basic datum of entanglement setups (eg., Bell tests) is called coincidental detection, and the rate of coincidental detection varies as a function of θ, the angular difference between the polarizer settings.
No, in the Bell test setup I described above, the basic datum is whether the experimenter sees a photon go through the polarizer or not. I think the word "correlation" is a much better term for what you call the "rate of coincidental detection". It is just the correlation between individual polarization measurements of photons, and as such all its properties are determined by whatever determines the results of individual polarization measurements. And the nonlinear relationship between the correlation and the angle is also entirely determined by whatever determines whether a photon goes through a polarizer or not.
So, given that the rate of individual detection doesn't vary as a function of polarizer setting, then what can you infer from this?
All a local determinist might infer from this is that the decision of whether to go through the polarizer or not is based on some local hidden variable, but we human beings don't know the value of this variable, so to us it seems like an unpredictable 50-50 chance whether it will go through.
No. Incorrect inference. This doesn't follow from the known experimental results.
But the argument is not based on the known data from practical experiments done so far; if you wanted to respond to Bell's theorem in that way you could be like zonde, who believes that Bell tests to date have experimental loopholes, and that quantum mechanics will be disproved as soon as we improve our experimental capabilities. The argument I'm making is more fundamental: it is that it is impossible for a local determinist to believe that all the experimental predictions of quantum mechanics are correct, without regard to the practical difficulties of testing these predictions. It took us a while to do any Bell tests at all, but that did not change the validity of Bell's theorem.
ThomasT
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#282
Mar5-12, 09:42 PM
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Quote Quote by lugita15
There is no experimental procedure called "coincidence detection" ...
Quote Quote by ThomasT
There's circuitry that matches detection attributes which operates according to calculations based on the photon emission source and the distance between the polarizers.
Quote Quote by lugita15
... so the term "rate of coincidence detection" is highly misleading. Coincidences aren't "detected" experimentally, they are a consequence of individual detections.
Quote Quote by ThomasT
They're a consequence of matching individual detection attributes wrt calculated coincidence intervals.
Quote Quote by lugita15
But these are just contingent facts about experimental design. Consider an idealized experiment where one photon pair is sent out every hour by a source which is exactly at the midpoint between two polarizers, which catch every single photon with perfect accuracy. In that case all each experimenter has as far as data goes is a list of yes or no answers as to whether the photon went through the polarizer or not. There are no time stamps, distance measurements, coincidence intervals, or anything like that.
But my reply was in reply to your reply that "there's no experimental procedure called 'coincidence detection'. And of course there is an experimental procedure called coincidence detection.

And in reply to that you propose an idealized experiment that has nothing to do with what we're talking about.

The fact of the matter is that wrt Bell tests there are time stamps, distance measurements, and coincidence intervals. So, you're going to have to deal with them.
lugita15
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#283
Mar5-12, 09:48 PM
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Quote Quote by ThomasT View Post
But my reply was in reply to your reply that "there's no experimental procedure called 'coincidence detection'. And of course there is an experimental procedure called coincidence detection.

And in reply to that you propose an idealized experiment that has nothing to do with what we're talking about.

The fact of the matter is that wrt Bell tests there are time stamps, distance measurements, and coincidence intervals. So, you're going to have to deal with them.
But we're not talking about the practical ability of Bell tests today to definitively disprove local determinism. (There are of course several experimental loopholes to Bell, and people like zonde rely on them to cling onto a local deterministic view, accepting the fact that future experiments may disprove their views.) We're discussing the deeper issue of whether a local determinist can believe that all the experimental predictions of quantum mechanics are true, and that includes what QM has to say about idealized setups like the one I outlined.
ThomasT
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#284
Mar5-12, 10:12 PM
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Quote Quote by lugita15 View Post
... in the Bell test setup I described above, the basic datum is whether the experimenter sees a photon go through the polarizer or not.
That's the basic datum for rate of individual detection. Wrt rate of coincidental detection, the basic datum is coincidental detection.

Quote Quote by lugita15 View Post
I think the word "correlation" is a much better term for what you call the "rate of coincidental detection".
Rate of coincidental detection has a specific technical meaning. It doesn't, by itself, refer to correlation. It refers to rate of coincidental detection.

Quote Quote by lugita15 View Post
It is just the correlation between individual polarization measurements of photons, and as such all its properties are determined by whatever determines the results of individual polarization measurements.
That's just incorrect. Rate of coincidental detection certainly does not refer to the correlation between individual polarization measurements of photons.

Bell test correlations refers to the correlation between the angular difference between the polarizers and the rate of coincidental detection.

Quote Quote by lugita15 View Post
And the nonlinear relationship between the correlation and the angle is also entirely determined by whatever determines whether a photon goes through a polarizer or not.
Also incorrect.

Here's what's known. The rate of individual detection doesn't vary with polarizer orientation. The rate of coincidental detection does vary with the angular difference between polarizer orientation. How can these two different experimental contexts be measuring the same underlying parameter?

Quote Quote by lugita15 View Post
... the argument is not based on the known data from practical experiments done so far ...
Well, no, your argument isn't. No offense, but from what you've written it doesn't seem that you're all that knowledgeable about Bell tests. Is that the case?

If so, just admit it and then DrC et al. can help you learn about them. They certainly helped me. I'm still more or less quite ignorant ... but a bit less so thanks to their help.
ThomasT
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Mar5-12, 10:22 PM
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Quote Quote by lugita15 View Post
But we're not talking about the practical ability of Bell tests today to definitively disprove local determinism.
Right, we're talking about the practical ability of Bell tests to definitively rule out Bell-type LR models of quantum entanglement, and how that can be explained in a way that still allows the assumptions of locality and determinism.

Quote Quote by lugita15 View Post
We're discussing the deeper issue of whether a local determinist can believe that all the experimental predictions of quantum mechanics are true, and that includes what QM has to say about idealized setups like the one I outlined.
No, it doesn't include idealized setups like the one you outlined because that idealized setup is a nonsequitur.

I've asked you a specific question, that you still haven't answered, about what you would infer from the experimental facts that, wrt Bell tests, the rate of individual detection does not vary as a function of polarizer orientation, while the rate of coincidental detection does vary as a function of the angular difference between polarizer orientations. So, what might you infer from this?
lugita15
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#286
Mar5-12, 10:44 PM
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Quote Quote by ThomasT View Post
Right, we're talking about the practical ability of Bell tests to definitively disprove Bell-type LR models of quantum entanglement, and how that can be explained in a way that still allows the assumptions of locality and determinism.
If that's your only point, then you and I have no quarrel. Not only am I willing to concede that the philosophical stance you call local determinism has not been ruled out by experiment, I am also willing to concede that what you call the "Bell-type LR models of quantum entanglement" have not been definitively disproven, due to various kinds of experimental loopholes, and there is reason to believe that we might not be able to do a loophole-free Bell test for the forseeable future.
No, it doesn't include idealized setups like the one you outlined because that idealized setup is a nonsequitur.
Why is it a nonsequitur? What I am trying to argue is that a local determinist must disagree with at least some of the experimental predictions of quantum mechanics. The particular predictions he disagrees with might be difficult or nearly impossible from a practical point of view to test (as in the case of my idealized setup), but the disagreement exists all the same. To answer the OP's question, this is why local determinism is not usually considered an acceptable interpretation of quantum mechanics, unlike the many worlds interpretation or nonlocal deterministic interpretations like Bohmian mechanics. In a (non-superdeterministic) local deterministic universe, there must exist an experiment which disproves quantum mechanics. This is, in my view, the heart of Bell's theorem. Do you disagree with this?
I've asked you a specific question, that you still haven't answered, about what you would infer from the experimental facts that, wrt Bell tests, the rate of individual detection does not vary as a function of polarizer orientation, while the rate of coincidental detection does vary as a function of the angular difference between polarizer orientations. So, what might you infer from this?
I responded to your question in a previous post of mine, but I probably didn't do justice to whatever your intent was:
"All a local determinist might infer from this is that the decision of whether to go through the polarizer or not is based on some local hidden variable, but we human beings don't know the value of this variable, so to us it seems like an unpredictable 50-50 chance whether it will go through." And I'll add that a local determinist would say that the reason a comparison of individual detection results yields a correlation which depends on the relative angle of the polarizers is that both photons contain the same basic hidden variable information, so when we turn our polarizers to different angles we're finding out different parts of this shared information.
ThomasT
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Mar5-12, 11:56 PM
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Quote Quote by lugita15 View Post
What I am trying to argue is that a local determinist must disagree with at least some of the experimental predictions of quantum mechanics.
And at least one of the things that I'm trying to argue is that a local determinist doesn't have to disagee with any of the experimental predictions of QM.

Quote Quote by lugita15 View Post
In a (non-superdeterministic) local deterministic universe, there must exist an experiment which disproves quantum mechanics.
Why? QM is in certain respects a nonmechanistic acausal theory, and certainly wrt the quantum entanglements produced via Bell tests. Whether QM is at odds with local determinism is pretty much a matter of interpretation as far as I can tell.

Quote Quote by lugita15 View Post
This is, in my view, the heart of Bell's theorem. Do you disagree with this?
I think that Bell's theorem showed that an LR model of quantum entanglement encoding certain constraints is necessarily incompatible with standard QM. No more, and no less.

Quote Quote by lugita15 View Post
I responded to your question in a previous post of mine, but I probably didn't do justice to whatever your intent was ...
It's a straightforward question. Here it is again.

Wrt Bell tests, the rate of individual detection does not vary as a function of polarizer orientation, while the rate of coincidental detection does vary as a function of the angular difference between polarizer orientations.

What might you infer from this?
Demystifier
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Mar6-12, 01:20 AM
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Quote Quote by lugita15 View Post
Demystifer, if pilot waves don't go faster than light, then what explains the nonlocality of entanglement? Does the quantum potential propagate faster than light?
Bohmian mechanics (BM) is not nonlocal because something propagates faster than light. Instead, BM is nonlocal because velocity and acceleration of one particle at a given time depends on the positions of other particles (with which it is entangled) at the same time, no matter haw far these particles are.

Quote Quote by lugita15 View Post
Also, am I wrong in my impression that a particle's trajectory right now is determined in part by the apparatuses it knows, based on nonlocal interaction, that it's going to encounter later?
In the context of nonrelativistic BM, you are wrong. In the context of relativistic BM, the answer depends on what exactly do you mean by "later".


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