why is superdeterminism not the universally accepted explanation of nonlocality?

ThomasT

This is a bit vague. And I think that QM and SR have already been reconciled in the form of quantum field theory. Which I'm not fluent in.

By the way, I appreciate your posts, but try to stay on topic.

I'm going to go back and read the preceding several pages because it seems that you've had a lot to say. Give me at least 30 minutes. And if there's any point that you'd like to make that you think is important to the thread topic that you haven't already made, then let's hear it.

EDIT: jadrian, my apologies. I recall now that you're the original poster (the OP, which can refer to original poster, or original post).

Well then, perhaps you might synopsize your assessment of the thread thus far ... and we'll take it from there.

jadrian

u cant rule out the possibility of a model that could

jadrian

wear a poncho its a bit of a ****storm. i learned alot along the way but its hard for me to blindly accept assertations from someone who thinks he is alive in the traditional sense and believes he chooses his future as if isolated from very basic laws of physics and the universe itself

ThomasT

Not sure what this means or what it's in response to.

ThomasT

If you used billiard balls, then it wouldn't be a Bell test. You could model any billiard ball test using classical mechanics.

jadrian

dr chineses assertions

ThomasT

Ah. Ok, still not sure about it. But that's ok. A bit off-topic. Of course it's your topic, so I guess you can swerve a bit now and then, so to speak. Not sure about the rules on that.

Anyway, yeah, I agree that it's generally not a good idea to blindly accept assertions from anybody, though, in my experience, DrC's assertions are generally pretty good. But nevertheless check them out.

jadrian

yeah i didnt understand the part 2 of superdeterminism when i made this thread. i should have just said determinism

metacristi

The idea that Nature conspire somehow to produce the results observed in Aspect, Gisin, Zeilinger and so on type of experiments (which do not necessarily involve strong determinism but only the existence of some pre-determinism at Planck level, no counterfactual definiteness in the experiments) is still a solution to the problem no doubt. And it is by no means above science. Unfortunately at this time this program is far from being even remotely close to the alternative programs which accept counterfactual definiteness in the experiments.

But this does not mean that it cannot become progressive in the future. We must remain open to this. In my view this is the best decision at this moment in time, inventing another 'no-go theorem' in this case (extremely shaky anyway) is at least counter-productive (and which could even prove to be an error far worse than von Neumann's 'proof' that hidden variables are impossible). Happily some leading scientists take it seriously, among them t'Hooft:

http://arxiv.org/abs/hep-th/0104219
http://arxiv.org/abs/quant-ph/0212095
http://arxiv.org/abs/hep-th/0105105

lugita15

OK, and I think one thing that leads to misunderstanding is a terminology issue. You're using local determinism to refer to a philosophical stance, while you're using local realism to refer to a particular formal model which tries to implement this philosophical stance. I'm using both local realism and local determinism, pretty much interchangably, to refer to the philosophical stance, not to any formal model or formal constraint. So just keep that in mind when reading my posts.OK, let me try once more to show you how the logic of Bell's theorem forces any local determinist to disagree with at least some of the predictions of quantum mechanics.

1. Pretend you are a local determinist who believes that all the experimental predictions of quantum mechanics is correct.
2. One of these experimental predictions is that entangled photons are perfectly correlated when sent through polarizers oriented at the same angle.
3. From this you conclude that both photons are consulting the same function P(θ). If P(θ)=1, then the photon goes through the polarizer, and if it equals zero the photon does not go through.
4. Another experimental prediction of quantum mechanics is that if the polarizers are set at different angles, the mismatch (i.e. the lack of correlation) between the two photons is a function R(θ) of the relative angle between the polarizers.
5. From this you conclude that the probability that P(-30)≠P(0) is R(30), the probability that P(0)≠P(30) is R(30), and the probability that P(-30)≠P(30) is R(60).
6. It is a mathematical fact that if you have two events A and B, then the probability that at least one of these events occurs (in other words the probability that A or B occurs) is less than or equal to the probability that A occurs plus the probability that B occurs.
7. From this you conclude that the probability that P(-30)≠P(30) is less than or equal to the probability that that P(-30)≠P(0) plus the probability that P(0)≠P(30), or in other words R(60)≤R(30)+R(30)=2R(30).

Which of these steps do you disagree with and why?
But you're only agreeing that some particular formal model does not agree with the predictions of QM. In my 7-step argument above, I am trying to prove that ANY believer in local determinism MUST disagree with some of the predictions of QM. The reason that quantum mechanics is able to have both perfect correlation at identical angles and nonlinear correlations as a function of angle is that QM does not say that the decision about whether the photon goes through the polarizer or not is predetermined by a function P(θ). In particular, if one polarizer is turned to -30 degrees and the other polarizer is turned to 30 degrees, quantum mechanics doesn't believe that the photons have a definite polarization at 0 degrees, and thus QM does not believe in P(0) which is essential for the proof above.
Yes, it does. The proof above decisively shows that in any local determinist universe, we must have R(60)≤2R(30). But the way superdeterminism gets around this is by saying that it is impossible to get accurate measurements of R(30) and R(60), because the experiment is rigged: since whatever is controlling the measurement decision interacted in the past with the (ancestors of) the entangled photons, the experimenters are selecting the angles just right (because the particles controlling them know the exact details of the function P(θ) for the entangled pair of photons) so that it appears that R(60)>2R(30).

That's why I said the following to you earlier in this thread:

"So here's another way to put it: An ordinary local realist theory just assumes that particles which are considered entangled according to QM must have had local interactions in the past which is determining their EPR-type nonlocal correlations today. But a local superdeterminist theory assumes that a particle must have interacted in the past with not only those that are entangled with it according to quantum mechanics, but also other particles which quantum mechanics would say have no connection with it. This is how a local superdeterministic theory would be able to produce Bell-type nonlocal correlations."

And again, remember that when I say local realism I mean the philosophical stance you call local determinism.

lugita15

Yes, the local information will always show boring 50-50 results, and it's only when you make a slower-than-light comparison of the data that you are able to see the nonlocal correlation.

lugita15

Well, it depends on your terminology. It's as if the faster-than-light stuff has effects, but those effects cannot be discovered until you do slower-than-light communication or travel.

lugita15

So now that you understand what the part 2 is (conspiratorial initial conditions), do you consider yourself a nonlocal determinist like the Bohmians, as opposed to a superdeterminist?

DrChinese

I guess I just don't have what it takes... I feel so inadequate.

zonde

Malus' law does not describe correlations between two photons but intensity change for single beam of light.
Otherwise yes, I do agree that this doesn't work.

It's "fair sampling assumption not holding for photons" loophole.

lugita15

Yes, I was just using the term in a generalized sense to refer to sinusoidal θ-dependence. I hope we can convince ThomasT of that.
But surely, as technology improves, it should be fairly easy to send photons one at a time, have every pair be entangled, and have every pair be collected by a photon detector, so no sampling issue will arise. Also, haven't entanglement experiments been done on all kinds of things, including qubits in the context of quantum computing, so don't you need a more general objection to Bell's theorem than just photons?

DrChinese

You are correct, and you probably already know this, but most consider this to be a disproof of the fair sampling assumption:

http://www.nature.com/nature/journal.../409791a0.html

For reasons I do not fully understand, most local realists simply reject this by pointing out that the locality loophole (closed by Weihs et at in 1998) is not closed simultanoeously.