The QM predicted correlation isn't surprising if one takes into account the known behavior of light. Herbert's conclusion that the correlation between θ and rate of coincidental detection should be linear goes against what's known about light. So, it would seem that Herbert's conclusion is the more surprising one.harrylin said:
I think you're reading too much into it. We know that LR models give incorrect predictions. What is it in the models that causes their predictions to diverge from QM and experimental results? When this is ascertained, then the question is whether this informs wrt deep reality -- which, imo, it doesn't.gill1109 said:
I find it rather an unwarranted stretch. Randomness refers to unpredictable (experimental) phenomena.gill1109 said:
harrylin said:
Actually, zonde pointed out in post #26 that Herbert had the facts wrong. At best there are only a few published experiments that "closed the detection loophole", and I suspect that they were done with different set-ups than the one on which he based his proof.morrobay said:
It sounds to me as if you misunderstand Herbert's argument, and perhaps also what is meant with "localist". Please have a look at my post #20, in which I elaborated on Herbert's proof. Do you see an error, assuming that step 1 is correct?salvestrom said:
Thanks for reminding me of Bohmian models!gill1109 said:
I agree with you on this (finally, eh?lugita15 said:
).The words spontaneity and randomness refer to our ignorance of, and inability to specify the mechanics of, an assumed (if only tacitly) local deterministic evolution of a system from a prior state.gill1109 said:
What I found so great about Herbert's proof, is that it doesn't invoke lambda's and even not probabilities, but just direct comparisons of statistical measurement data. That is of course strongly related to probabilities, but it's great not to have to make that step.lugita15 said:
More or less so. Herbert simply uses the "fact" that when "aligning both SPOT detectors, No errors are observed." Thus his assumption is that detector settings do not affect whatever is sent towards the detectors, if that is what you mean
Please elaborate - you seem to suggest to have spotted another flaw in Herbert's proof, but it's not clear to me what you mean.ThomasT said:
No, that's not what I meant, but that's also an important assumption, known as the "no-conspiracy condition". There are people known as superdeterminists who try to get around Bell's theorem by violating this condition, e.g. by saying that the particles know in advance what the detector settings will be because the universe is totally deterministic, so the two particles use this information to coordinate in just the right way so that Bell's inequality appears to be false even though it would really be true if measurement decisions were free and independent. Superdeterminism is a pretty small fringe, but it counts Nobel laureate Gerard t'Hooft as one of it's adherents.harrylin said:
The "successful" local hidden variable models you're talking about, like the ones zonde was referring to, do not actually reproduce all the experimental predictions of quantum mechanics. Rather, they exploit some loophole or the other of Bell test experiments to say that Bell tests experiments to date have not definitively disproven their particular theories, but they claim that an "ideal experiment" would prove them right and QM wrong.harrylin said:
gill1109 said:
At any rate, it certainly implies an internal physical structure far beyond anything previously discovered. I would estimate that every particle must have some kind of local superdeterministic DNA to account for my Aunt Miriam and the radioactive sample. As well as for any other pairs of macroscopic selection devices, of which there would be many.That's the subtle detail that I disagree with: he speaks not about "would have been gotten" but about what "are observed". I think that that is a stronger argument.lugita15 said:
Herbert's proof asserts something slightly different from Bell's theorem, as I emphasised earlier: his claim isn't about theory but about facts of nature. What I called "successful" is to reproduce those measurement facts (real ones as opposed to imagined ones) with a "local realistic" model of which Herbert's proof asserts that they cannot be possibly reproduced by such a model.
But if the detectors are oriented at -30 degrees and 30 degrees, speaking about 0 degrees is clearly counterfactual reasoning. Herbert refers to the "binary message", the sequence of 0's and 1's you would have gotten if you oriented the detectors 0 degrees, and he considers mismatches between the -30 degree detector and the 30 degree detector to arise from deviations from this initial binary sequence. That is how he is able to say that a mismatch between -30 and 30 requires a mismatch between -30 and 0 or a mismatch between 0 and 30, and thus the percentage of mismatches between -30 and 30 is less than or equal to the percentage of mismatches between -30 and 0 plus the percentage of mismatches between 0 and 30.harrylin said:That's the subtle detail that I disagree with: he speaks not about "would have been gotten" but about what "are observed". I think that that is a stronger argument.
But the "facts of nature" that Herbert discusses have not been entirely confirmed by experiments in a way that skeptics cannot dispute. If you ask zonde, he will insist vehemently that current experiments do not allow you to definitively test the claim of quantum mechanics that entangled photons exhibit identical behavior at identical angles, due to various loopholes like fair sampling and detector efficiency that currently practical Bell tests fall victim to. But what Herbert is showing, and I think Bell was showing the same things, is that if we accept that quantum mechanics is completely right about all its experimental predictions, like identical behavior at identical angles, then no local hidden variable theory will be able to account all of these facts of nature.
But in Herbert's proof, we are talking about "imagined" measurement facts, at least for now, because the experiment he discusses is an ideal Bell test free from experimental loopholes, and we haven't done such a perfect experiment yet (although we're getting there...). But you're right, if the empirical facts of nature are as Herbert (and quantum mechanics) say they are, then the thesis that reality is local can be deemed rejected.
How did t'Hooft respond when you brought up this point to him?gill1109 said:
There you go again! And again I must reply: no, he refers to the sequence that he claims that you obtain each time when you orient the detectors 0 degrees. That is not about a conditional, hypothetical experience of a non-observed photon, but a factual experience of observed events. I found that really nice.lugita15 said:
What mattered to me was that Herbert made a seemingly rock solid claim about Nature and possible models of Nature that has been falsified - and I was frustrated because I did not find the error. Zonde was so kind to point the error out to me.
From reading up on this topic I discovered that there is some fuzziness about what exactly QM predicts for some real measurements; but the models that I heard about accurately reproduce what is measured in a typical Herbert set-up. Following your logic, we should conclude that QM is wrong. However, I think that that is not necessarily the case.
Well Herbert fooled me there - and apparently he was fooled himself.
harrylin said:
Let me try again. This is the crucial step where counterfactual definiteness is invoked: "Starting with two completely identical binary messages, if A's 30 degree turn introduces a 25% mismatch and B's 30 degree turn introduces a 25% mismatch." He is very clear, A's 30 degreee turn introduces a 25% mismatch from the 0 degree binary message. He is saying this even in the case when B has also turned his detector, so that no one is actually measuring this particular bit of the 0 degree binary message. The only bits of the 0 degree binary message that are actually observed are the ones for which one of the detectors was turned to 0 degrees. And yet he is asserting that even when neither of the detectors are pointed at 0 degrees, the mismatches between the two detectors still represent errors from the 0 degree binary message. Isn't discussion of deviation from unmeasured bits of a binary message a clear case of counterfactual definiteness, AKA realism?harrylin said:
Perhaps Herbert should have phrased his claim slightly less boldly, because various practical loopholes make it hard to perfectly do the experiment he is talking about. But while it is true that experimental limitations prevent us at the current moment from absolutely definitively ruling out all local hidden variable models, we're getting there quickly, as I think zonde has said.
Herbert is not making any "errors". The main point of the proof, even if Herbert didn't state it quite like this, is to to show that unless quantum mechanics is wrong about the experimental predictions it makes concerning entanglement, we can deem local hidden variable models to be ruled out.
No, there isn't.
First of all, the term "Herbert set-up" is a bit cringe-inducing; as Herbert himself says, "It has appeared in some textbooks as "Herbert's Proof" where I would have preferred "Herbert's Version of Bell's Proof"". (And as I told you before, although Herbert apparently came up with it independently, the -30, 0, 30 example was the one used by Bell when he tried to explain his proof to popular audiences.)
No, we shouldn't. If a perfect, loophole-free Bell test, like the one Herbert envisions, gave results consistent with the possibility of a local hidden variable model, then yes there may be just cause to abandon QM. But until that time, how can you conclude such a thing from the logic?
No, I don't think so. The only point I'd concede is that he might want to qualify his remarks in all caps that "NO CONCEIVABLE LOCAL REALITY CAN UNDERLIE THE LOCAL QUANTUM FACTS." If he added "ASSUMING THAT THEY ARE INDEED FACTS, WHICH THEY SEEM TO BE", then it would be fine.Well Herbert fooled me there - and apparently he was fooled himself.
I was thinking of for example Bell's idea about experiments that he seems to have thought that according to QM are possible, but that until now were not possible in reality; and for example Weih's experiment, which yields results of which the exact QM predictions are unclear for large time windows. Maybe we should start a discussion topic about that?DrChinese said:
Sorry, I never understood such discussions and words - which is why I prefer Herbert's formulation, and even Bell's. And I already stated how I interpret that: we assume that the rotation of the detector doesn't affect the stream of whatever is coming towards the detector. If people call that "counterfactual definitness", that's fine to me. It's certainly what I call "local realism" aka "no spooky action at a distance".lugita15 said:
Sure - my point was that he presented non-facts as facts, and I fell into that trap.
Not a flaw in Herbert's proof. But in his interpretation of the physical meaning of his proof.harrylin said:
Of course. And that's all that Bell's theorem applies to. As billschneider has said repeatedly.gill1109 said:
His proof is a proof (or so he claims) about the physical meaning of observations.ThomasT said:
Note: in a subsequent thread on why hidden variables imply a linear relationship, it became clear that imperfect detection is not the only flaw in Herbert's claim about facts of measurement reality; another issue that Herbert missed is the effect of data picking such as with time coincidence windows.harrylin said:
There are, of course, numerous experimental loopholes in current Bell tests. Herbert isn't concerned with loopholes. The point is that the local determinism is fundamentally in contradiction with the empirical predictions of QM. Whether this empirical disagreement is practically testable given current experimental limitations is, to me, beside the point.harrylin said:
Obviously we continue to disagree about what Herbert claimed to have proved; but everyone can read Herbert's claims and we have sufficiently discussed that.lugita15 said:
I completely agree with you that Herbert worded his conclusion a bit too strongly, because he took for granted that QM is correct in its experimental predictions, an assumption that has overwhelming evidence backing it up, but not definitive proof due to various loopholes like detector efficiency.harrylin said: