What this means is that one of the following three assumptions must be wrong:No, all three assumptions are completely consistent with textbook treatments of quantum mechanics.1. No Superdeterminism.
2. Measurements have definite outcomes.
3. No spooky action at a distance.The absence of superdeterminism is sometimes called “Free choice” or “Free will”, but really it has nothing to do with free will. Needless to say, I think what’s wrong is rejecting superdeterminism.
Superdeterminism says that all of your choices have been completely determined since the Big Bang. Yes, it is directly contrary to free will. There are philosophical compatibilists who are that you can think of yourself as having free will, even tho you don't. But that is not free will. It is just the illusion of free will.
One such philosopher is Daniel Dennett who argues that all your choices are determined, but that it would be irresponsible to tell people that they have no free will. He makes a good argument that disbelief in free will is destructive.
Everyone says measurements have definite outcomes, except the many-worlds advocates. As I have argued else, many-worlds is unscientific nonsense. So is superdeterminism. I criticized her superdeterminism, and also here, here, and here.
That leaves spooky action. There is no experiment showing spooky action, and it is foolish to believe in it. They only show spooky action if make another assumption, namely hidden variables, and that assumption was properly rejected decades ago.
Hossenfelder says "physicists would rather throw up objective reality". That is true, if objective reality means that every electron has a precise position and momentum, whether measured or not. That is impossible, by the uncertainty principle. But the measurements are definite, and objectively real.
Update: Commenter Andrei, probably the same one who comments below, asks:
Are the measured spins predetermined or not? If not how do you think the results are anticorrelated?I guess he is suggesting that the spins are predetermined by a superdeterminism. Aaronson answers:
The Bell inequality shows that the measured spins cannot be “predetermined,” under minimal assumptions of no superluminal signalling and no insane cosmic conspiracies. ...Here, "predetermined" is the opposite of "random". A lot of people take the Bell test experiments as proof of randomness. A lot of others believe in determinism. A very small number believe in superdeterminism.More broadly, the idea that there are only two possibilities,
(1) local hidden variables or
(2) superluminal signalling,with nothing intermediate between the two, is a perfect example of the “classical baggage” that the Zen anti-interpretation of quantum mechanics counsels us to discard.
I do not think that the experiments can tell us whether the spins are predetermined.
I do agree with Aaronson that local hidden variables and superlumninal signaling are the only possibilities. In fact, I would say that both of those have been ruled out.
Dear Roger,
ReplyDelete"all three assumptions are completely consistent with textbook treatments of quantum mechanics"
I don't think there are textbooks treating superdeterminism, and even locality/non-locality in a serious way. Still, it can be proven beyond any reasonable doubt that superdeterminism is required if locality is preserved.
I present below an argument based on the EPR-Bohm experiment proving that locality implies determinism (the measured values are predetermined):
At two distant locations (A and B) you can measure the X-spin of an entangled pair. QM predicts that:
P1: If you measure the X-spin at A you can predict with certainty (probability 1) the X-spin at B.
Let’s exclude non-locality:
P2: the X-spin at B is not determined by the measurement at A.
From P1 and P2 it follows that there was something at B that determined the result of the B measurement. EPR named that “something” an “element of reality”. So:
P3: There is an element of reality at B that determines the measurement result at B.
You may observe that there is no other logical option available (unless you think that it’s by pure luck that we manage to always predict with certainty the X-spin at B, which is rather absurd).
From P1 and P3 it follows:
P4: there was an element of reality at A that determined the measurement at A.
This is because once we’ve established that the measurement at B was fixed (P3) it’s impossible that the measurement at A could have been different, right?
OK, so P3 and P4 lead to:
C: The X-spin of both particles, at A and B were determined before any measurement took place (deterministic realism).
Now we can look at Bell's theorem that establishes that the only way to reproduce QM by a hidden variable theory (deterministic realism above) is to deny the freedom (independence) assumption, which means superdeterminism.
In conclusion, locality requires superdeterminism.
To continue...
Cont:
ReplyDelete"Superdeterminism says that all of your choices have been completely determined since the Big Bang."
This is not an implication of superdeterminism but of determinism. Any deterministic theory implies that.
"As I have argued else, many-worlds is unscientific nonsense."
I agree with that.
"So is superdeterminism."
Why? Superdeterminism implies that there are correlations between the distant experimental subsystems involved in a Bell test. There is nothing peculiar about that. We are surrounded by distant systems showing correlations. Orbiting stars, planets in a planetary system, stars in a galaxy, electrons in an atom, synchronized clocks are trivial examples of this sort. The origin of those correlations consists in long-range field interactions (gravitational, electromagnetic). Such interactions certainly occur between the source and detectors involved in a Bell test, as they are built from electrons and nuclei, charged, massive particles. Those interactions could lead to macroscopic correlations, providing a physical mechanism for superdeterminism.
"That leaves spooky action. There is no experiment showing spooky action, and it is foolish to believe in it."
Agreed.
"They only show spooky action if make another assumption, namely hidden variables"
No, the reality is opposite. As the above argument proves, hidden variables are the only way to avoid spooky action.
"that assumption was properly rejected decades ago"
This is false. Bohr identified some problems with the original EPR argument, but there was never a proper rebuttal of the EPR-Bohm one. My above argument stands unrefuted.
"Hossenfelder says "physicists would rather throw up objective reality". That is true, if objective reality means that every electron has a precise position and momentum, whether measured or not. That is impossible, by the uncertainty principle."
This is a misunderstanding of the uncertainty principle. Uncertainty does not imply non-existence. It's just that you are uncertain about the properties of the particle. The particle might very well have well defined properties.
In your scenario, A and B are identical particles emitted from the same source, so they have an element of reality in common. This element of reality is local in nature, and has nothing to do with any measurement or spooky action. That is just standard QM.
ReplyDeleteBell showed that if the element of reality is modeled by local hidden variables, then it contradicts QM. So everyone rejects that.
Thus you can either believe in QM and locality, or in spooky hidden variables.
I will add some links to my opinions on superdeterminism. I posted today on many-worlds, as well as previously.
Roger,
Delete"In your scenario, A and B are identical particles emitted from the same source, so they have an element of reality in common. This element of reality is local in nature, and has nothing to do with any measurement or spooky action."
If the element of reality has nothing to do with the measurement then the measurement result does not depend on it, so your claim is that P3 is false.
On the other hand P3 logically follows from P1 and P2. P1 is a prediction of QM, so I assume that you accept it as true, therefore P2 must be false, so you get non-locality (spooky action). This is exactly my point. Locality requires hidden variables.
"Bell showed that if the element of reality is modeled by local hidden variables, then it contradicts QM."
Only if the hidden variables do not depend on the detectors' settings. I see no reason to make such an assumption.
"So everyone rejects that."
't Hooft does not reject that and neither Sabine Hossenfelder. Anyway, the truth is not established by how accepted or rejected an idea is, but on logical arguments. There are no sound arguments against superdeterminism.
"Thus you can either believe in QM and locality, or in spooky hidden variables."
Please look again at my argument. You've got it all wrong. Without hidden variables you get the spooky stuff.
Superdeterminism is like solipsism and many-worlds, in that it cannot be proven false. It is just a philosophical belief.
ReplyDeleteNo, I am not saying that P3 is false. All measurements are dependent on whatever realities are involved. Within the backward cone, so no spooky causes.
You are right that Bell did not rule out superdeterminism. He admits that.
Locality does not require hidden variables. Quantum field theory is a local theory, without hidden variables.
Roger,
ReplyDelete"Superdeterminism is like solipsism and many-worlds, in that it cannot be proven false."
Superdeterminism is a generic class of theories, just like determinism or non-determinism. In principle it could contain an infinite number of such theories, so it is unlikely to be able to falsify it. But this is also true for deterministic or non-deterministic theories, so if superdeterminism is "just a philosophical belief" so are those.
On the other hand a well defined superdeterministic theory can be falsified just as easy as a non-deterministic one. Remember, superdeterminism implies that in a Bell test the hidden variable does depend on the detectors' states. There is nothing unfalsifiable about comparing some physical states.
"I am not saying that P3 is false."
If P3 is true, "there is an element of reality at B that determines the measurement result at B", so the measurement results are predetermined (by that element of reality, the so-called hidden variable). Are we in agreement here?
"Locality does not require hidden variables."
Yet, you just agreed with P3 that postulates the existence of hidden variables. You see that denying P3 leads to non-locality, so, indeed, without hidden variables the theory is non-local.
"Quantum field theory is a local theory, without hidden variables."
It is local in the sense that you cannot send faster than light signals with it. There is a theorem that you cannot use entanglement to send such signals. But here we are not discussing such signals, but the possible existence of instantaneous communication between the entangled particles. From this point of view QFT might be local or non-local.
Yes, superdeterminism could contain an infinite number of theories, just like solipsism, many-worlds, astrology, and all the other philosophical beliefs that have no relation to the real world.
ReplyDelete"P3 that postulates the existence of hidden variables"
Certainly not. P3 says nothing about hidden variables. If you want to postulate hidden variables, then go ahead, but they have been shown to be false.
You are falling into a trap that Bell used in his later paper. He could not convince anyone of his hidden variables assumption, so he just started pretending that it was true without postulating it.
"Yes, superdeterminism could contain an infinite number of theories, just like solipsism, many-worlds, astrology, and all the other philosophical beliefs that have no relation to the real world."
ReplyDeleteOK, let's try to make your argument more explicit.
Premise 1: Superdeterminism, as a class of theories, is not falsifiable
Premise 2: If a theory is from a class that is itself unfalsifiable, that theory is also unfalsifiable.
Premise 3: If a theory is unfalsifiable it's not science.
Conclusion: Superdeterminism is not science.
I'll show that the argument above (I hope I do not misrepresent it) is not sound because both premises 1 and 2 are false.
As a subclass of determinism, superdeterminism cannot be less falsifiable than determinism itself. But determinism is falsifiable (put a system in a certain initial state many times and see if the evolution is unique), therefore superdeterminism is also falsifiable. Premise 1 is false.
Let's assume that Premise 1 is true, for the sake of the argument. We have:
Premise 2: If a theory (say general relativity) is from a class that is itself unfalsifiable (determinism), that theory is also unfalsifiable.
GR is certainly falsifiable, therefore Premise 2 is false.
Your argument fails.
Now let me explain what superdeterminism really is.
According to Bell, a superdeterministic theory denies the freedom/independence assumption, meaning that it posits that the states of detectors at the time of detection and the state of the source at the time of emission are not independent, they are correlated.
OK, there is nothing absurd or unlikely about that. There are correlated systems all over the place. Electrons in an atom, atoms in a crystal, planets in a planetary system, stars in a galaxy are all examples of objects being correlated in various ways. The reason behind those correlations is always a field interaction. Planets and stars interact through gravitational fields, electrons and atoms through electric and magnetic fields. An interaction always determines a correlation, because the presence of an interaction imposes constraints on how the objects in a system move. The only way to guarantee that no correlations exist is to make sure no interactions exist.
Let's now go back to our Bell test. Do detectors and particle sources interact in a Bell test? You bet. They consist of atoms, so electrons and nuclei. Electrons and nuclei are both massive and charged so they interact electromagnetically and gravitationally. So, a correlation between the physical states of the source and detectors are to be expected. This is superdeterminism.
To make my claim clear, I need to add that the above argument does not say anything about the specific correlations that are to be expected. They might explain the Bell test results or not. The only way to check that is to calculate them. This is not going to be easy, but it is certainly possible, and the result would either confirm or falsify this hypothesis.
To cont...
Cont...
ReplyDelete"P3 says nothing about hidden variables."
Of course it does. The element of reality, that is not part of the quantum formalism, is the additional element that needs to complete QM in order to make it local. That element is known as a "hidden variable".
"If you want to postulate hidden variables, then go ahead, but they have been shown to be false."
As my argument shows, there is no need to postulate them. They follow from the locality condition.
"He could not convince anyone of his hidden variables assumption, so he just started pretending that it was true without postulating it."
Please read at least the abstract of Bell's seminal paper, "On the Einstein Podolsky Rosen Paradox". You can find it here:
https://cds.cern.ch/record/111654/files/vol1p195-200_001.pdf
A little quote:
"THE paradox of Einstein, Podolsky and Rosen [1] was advanced as an argument that quantum mechanics could not be a complete theory but should be supplemented by additional variables. These additional variables were to restore to the theory causality and locality."
Why are the hidden variable needed? To "restore causality and locality". Without them you need non-locality. It's not about convincing people by postulating useless staff.
Now you say P3 postulates hidden variables. Okay, but it is a bit like postulating a Flat Earth. But then you say that you are not postulating hidden variables. Make up your mind. Believe in hidden variables if you want, but the idea is contradicted by a century of Physics.
ReplyDeleteYou quote Bell, but the next sentence admits that hidden variables were "shown to be incompatible with the statistical predictions of quantum mechanics." That is why they are rejected today.
Then you fall back on superdeterminism, because it rejects all those statistical predictions of quantum mechanics. Most people would probably say that falsifies superdeterminism. But you're right, you can still believe in it, like solipsism, because you are rejecting 99+% of modern science. You are essentially denying that it is even possible to do experiments to test a theory. Yes, if you deny that, then you are free to believe in superdeterminism or any other fantasy.
"Now you say P3 postulates hidden variables."
ReplyDeleteYes, this is what P3 says.
"Okay, but it is a bit like postulating a Flat Earth."
No, because we have an impressive body of evidence that the Earth is not flat. We have no evidence that hidden variables do not exist.
"But then you say that you are not postulating hidden variables."
Exactly. My argument proves that we "HAVE TO" accept P3 as true IF locality is true. It is the locality condition, P2 that I hold as true. I am open to the idea that P3 is false, but, as you can see by looking at my argument, it's logically impossible for P3 to be false and P2 to be true. I think we have extremely good evidence that the universe is local, so I am forced to accept the truth of P3.
"Believe in hidden variables if you want, but the idea is contradicted by a century of Physics."
As I said, I do not take P3 on faith. P3 is imposed on me by logic, and if you value logic you should also accept P3, or accept non-locality (spooky action at a distance) or point to an error in the argument. There is really no other way and pointing to a century of wrong believes cannot change that.
The reason for rejecting hidden variables by most physicists is:
1. The original EPR argument had some flaws that Bohr speculated. Those were corrected by Bohm's version with spin, but interestingly, Bohr never commented on it. As I said there is no published rebuttal of the above argument. If you know of such rebuttal, please point it to me.
"You quote Bell, but the next sentence admits that hidden variables were "shown to be incompatible with the statistical predictions of quantum mechanics.""
Yes, if Bell's assumptions are correct. If you assume they are correct, the conclusion is that physics is non-local, not that there are no hidden variables. But again, I think that locality is too well established so I think it is more likely that the other assumption used by Bell is false (the independence condition).
"That is why they are rejected today."
This is a big mistake, because those physicists rejecting hidden variables do not actually accept Bell's conclusion, that in this case physics is non-local. Their reasoning is fallacious.
"Then you fall back on superdeterminism, because it rejects all those statistical predictions of quantum mechanics."
I "fall back on superdeterminism" because this is the only local option on the table and I think, based on evidence, locality is true.
It is not true that superdeterminism rejects QM's prediction. This is a serious misunderstanding on your part. What superdeterminism rejects is that the hidden variables and the states of the detectors are independent. This does not contradict in any way QM. QM will agree that interacting objects are not independent. The independence assumption is not based on any physics, is contrary to what both classical and quantum physics posit. It's just an intuition.
"But you're right, you can still believe in it, like solipsism, because you are rejecting 99+% of modern science."
I reject no science. Please specify what principle of science is contradicting superdeterminism! There is none.
"You are essentially denying that it is even possible to do experiments to test a theory."
Where did I make such a claim? I repeat, superdeterminism logically follows from the locality condition, it's not assumed. You can also verify superdeterminism by analyzing the physics (EM interactions) between source and detectors.
I'm currious, what is your local explanation of the EPR-Bohm experiment my argument uses without hidden variables? What is the explanation put forward by those 99% of physicists? If you are right, it should be easy to spell it.
No, Bell's paper says nothing about whether physics is local or non-local. It only says something about hidden variable theories. Just read the paper you linked above.
ReplyDeleteYou say that superdeterminism rejects the statistical independence of the detectors. It is a consequence that is rejects that statistical predictions of QM. That is what Bell said, and I agree.
The common explanation of EPR Bohm is QM, as described in QM textbooks. It does not use hidden variables, non-locality, or superdeterminism. You are the one who is taking a position contrary to a century of textbooks.
You say "P3 is imposed on me by logic", but that is simply false.
"No, Bell's paper says nothing about whether physics is local or non-local."
ReplyDeleteBell says that hidden variables are required to restore locality:
"These additional variables were to restore to the theory causality and locality"
He concludes that they cannot:
"It is
the requirement of locality, or more precisely that the result of a measurement on one system be unaffected by operations on a distant system with which it has interacted in the past, that creates the essential difficulty"
If the way to restore locality (hidden variables) do not work, it follows that locality cannot be restored.
"You say that superdeterminism rejects the statistical independence of the detectors."
Indeed, this is what superdeterminism is.
"It is a consequence that is rejects that statistical predictions of QM. That is what Bell said, and I agree."
Please provide a quote here! This is not what Bell said. Just look at Wikipedia or at any paper discussing superdeterminism. From here:
https://en.wikipedia.org/wiki/Superdeterminism
"In quantum mechanics, superdeterminism is a loophole in Bell's theorem, that allows one to evade it by postulating that all systems being measured are causally correlated with the choices of which measurements to make on them.[1] It is conceivable that someone could exploit this loophole to construct a local hidden variable theory that reproduces the predictions of quantum mechanics."
OK, superdeterminism is used to reproduce QM's predictions, not to reject them. You are in deep confusion here.
"The common explanation of EPR Bohm is QM, as described in QM textbooks."
No explanation is usually given, but I'm ready to hear it from you.
"It does not use hidden variables, non-locality, or superdeterminism."
Not explicitly, maybe, but the collapse of the wavefunction is a non-local process. As far as I can tell those textbooks present the collapse and don't explain at all how it is local. Again, I'm ready to hear it from you.
"You say "P3 is imposed on me by logic", but that is simply false."
P3 follows from P1 and P2. You can either make P1 false, or P2 false, or explain why P3 does not actualy follow. This is the only logical way to refute an argument. Just asserting that the conclusion is false does not work. Sorry!
You continue to make logic errors, and to misread Bell. Yes, Bell says that he tries a classical model of local hidden variables, and finds that it conflicts with QM predictions that were later confirmed by experiment. The conclusion is that local hidden variables do not work. It says nothing about locality in QM or anything else.
ReplyDeleteYou ask for the Bell quote, and he says "shown to be incompatible with the statistical predictions of quantum mechanics." It is in the first paragraph of the 1964 paper you linked above.
QM makes statistical predictions by using the statistical independence of the detectors. Superdeterminism rejects that. You agreed that superdeterminism rejects that.
Superdeterminism rejects almost all of modern science, and replaces it with nothing. There is nothing that can be said in its favor.
Roger,
DeleteFirst, I need to mention that you abandoned to refute my very simple argument based on EPR-Bohm experiment. You have not decided if a premise is false and you did not provide any reason why the argument is not sound. So, I need to conclude that you cannot provide a valid rebuttal but you are unwilling to admit defeat. This is OK, I've seen this behavior many times before.
"You ask for the Bell quote, and he says "shown to be incompatible with the statistical predictions of quantum mechanics." It is in the first paragraph of the 1964 paper you linked above."
I've asked for a quote about superdeterminism rejecting QM's predictions as you claimed. Bell's quote above is not about that, it's about those theories that are within the scope of his theorem.
"QM makes statistical predictions by using the statistical independence of the detectors."
This is false. Show me a textbook, paper, or any other material where "the statistical independence of the detectors" is a postulate of QM. Statistical independence does not have anything to do with QM. It is an assumption made by Bell in order to derive his theorem.
"You agreed that superdeterminism rejects that."
Indeed, but as pointed above, QM does not depend on that assumption at all. In general, QM says nothing about detectors or measurement except that the results are given by Born's rule. It is Bell's theorem that requires the independence assumption and it is by denying that assumption that superdeterminism can, in theory, reproduce QM's predictions in a local way. Just think about why would anyone want a theory that fails to reproduce QM? Such a theory would be already falsified because QM's predictions are now a well attested experimental fact.
"Superdeterminism rejects almost all of modern science, and replaces it with nothing."
This is an unproven assertion.
I understand that you take the so-called "common knowledge" for granted. This is somehow strange coming from someone claiming that Einstein is a myth. Don't get me wrong, I mostly agree with you on that (at least in regards to special relativity). But Einstein was right about QM being incomplete and Bohr was wrong. The argument here that stands unrefuted is a proof of that.
For a very good explanation of EPR and Bell I suggest you read Tim Maudlin's paper "What Bell did" here:
https://arxiv.org/ftp/arxiv/papers/1408/1408.1826.pdf
I debated Maudlin a lot on the issue of superdeterminism (he rejects it as you do) so it's not a paper in my favor. But is a good analysis of the options one has after taking EPR and Bell into account. Maudlin just accepts the non-local route (de Broglie-Bohm's theory) as the better one.
Yes, I did refute your argument. You contradicted yourself about whether you were assuming hidden variables, and that contradiction is fatal to your argument.
ReplyDeleteMaudlin gets this stuff wrong, and believes in nonlocal nonsense. I suggest reading the Wikipedia page on the subject, or any of a lot of other mainstream physics sources. I see that in that article, Maudlin rejects some sensible mainstream accounts of the subject. Maudlin is the one with the fringe view.
You don't believe that superdeterminism rejects almost all of modern science? Okay, show me some part of modern science that is compatible with superdeterminism. I cannot think of anything. No physics, chemistry, biology, social science, or anything else.
I didn't say that the statistical independence of the detectors is a postulate of QM. But it is essential to the experiments confirming QM. And hence essential to making use of the statistical predictions of QM.
Bell's quote is that he shows that a local hidden variable theory is incompatible with the statistical predictions of QM. That is true even if the theory is superdeterministic. Superdeterminism is still a loophole to the Bell test experiments, as superdeterminism is just a philosophical idea that no one can test. So I am not sure why you are arguing about the Bell quote that I gave you. Bell did say it, and he was correct about that.
"Yes, I did refute your argument. You contradicted yourself about whether you were assuming hidden variables"
ReplyDeleteYou did not refute anything. Let's focus on the first part of the argument:
At two distant locations (A and B) you can measure the X-spin of an entangled pair. QM predicts that:
P1: If you measure the X-spin at A you can predict with certainty (probability 1) the X-spin at B.
Let’s exclude non-locality:
P2: the X-spin at B is not determined by the measurement at A.
From P1 and P2 it follows that there was something at B that determined the result of the B measurement. EPR named that “something” an “element of reality”. So:
P3: There is an element of reality at B that determines the measurement result at B.
Do you accept that P3 follows from P1 and P2 or not? If not, why not?
"Maudlin gets this stuff wrong, and believes in nonlocal nonsense."
It would be helpful if you could point out where his line of reasoning is faulty. He presents an argument, not what he believes. If you disagree with his conclusion you need to attack his premises or his deductions.
"I see that in that article, Maudlin rejects some sensible mainstream accounts of the subject."
Please provide me with such a mainstream account on the subject. I cannot comment otherwise.
"You don't believe that superdeterminism rejects almost all of modern science? Okay, show me some part of modern science that is compatible with superdeterminism."
If we agree on the correct definition of superdeterminism (a local hidden variable theory that reproduces QM's predictions) then I've already answered this question. Such a superdeterministic theory would have the same predictions as QM so it will be compatible with all science that agrees with QM.
"I cannot think of anything. No physics, chemistry, biology, social science, or anything else."
All those are compatible with QM, so they will be compatible with a superdeterministic theory that gives the same predictions as QM.
Again, your concept of superdeterminism is absurd. Nobody wants to develop a theory that, as you say, rejects QM's predictions for the obvious reason that such a theory would be falsified from birth. I guarantee you that 't Hooft does not try to do that.
"I didn't say that the statistical independence of the detectors is a postulate of QM. But it is essential to the experiments confirming QM. And hence essential to making use of the statistical predictions of QM."
I fail to see your point here. For example QM predicts that a certain molecule is stable, or not. I can prepare that molecule and test its stability without assuming anything about the detector. The same holds for any pther prediction including Bell correlations. I know that the spins of two entangled particles are always found to be anticorrelated. Neither the prediction itself, nor its verification or practical use involves any assumption regarding the independence of the detector.
"Bell's quote is that he shows that a local hidden variable theory is incompatible with the statistical predictions of QM."
This is true only if the assumptions he uses in the derivation of his theorem are true for that theory.
"That is true even if the theory is superdeterministic."
No, because superdeterminism denies the independence assumption. Without this assumption the theorem is not mathematically valid.
"Superdeterminism is still a loophole to the Bell test experiments, as superdeterminism is just a philosophical idea that no one can test."
No, superdeterminism is not an experimental loophole. Those are about imperfect experiments, like the detection loophole (not all pairs are detected). Superdeterminism works even if the experiment works perfectly. It is a theoretical loophole, similar with non-locality.
"So I am not sure why you are arguing about the Bell quote that I gave you."
See above.
I've just noticed that a new paper by 't Hooft is out:
ReplyDelete"Explicit construction of Local Hidden Variables for any quantum theory up to any desired accuracy"
https://arxiv.org/pdf/2103.04335.pdf
I'm not going to comment if 't Hooft's model succeds or not, but this shows what superdeterminism is about: reproducing QM with local hidden variables. It's not rejecting QM, but finding a more fundamental, local theory from which QM emerges.
The tHooft paper is amusing, but it is not really a scientific theory or a superdeterministic theory that makes predictions. It is just a mathematical construction to defend some philosophical stance.
ReplyDeleteNo, P3 does not follow, as you have explained it. In fact, P3 has been disproved. To the extent that you and Maudlin argue for P3, you are just expressing a philosophical belief that is contrary to a century of physics.
Maudlin complains about this: "Except quantum mechanics agrees with experiments extremely well. And even people who have tried to make so---called hidden variables theories, which means that there is sort of a secret proper state that we don't know about, can't seem to do it. Bell's theorem actually says it's impossible."
All of that is true. Maudlin just doesn't want to accept it. It is also true that Einstein was a determinist who hated the probabilities.
Also, you say that the QM predictions about Bell correlations do not depend on assumptions about independence of the detectors. That is false. The predicted correlations do make that assumption. And that is why a superdeterministic theory cannot predict the Bell correlations. Instead, the superdeterministic theory blindly declares that the experiment cannot be done.
ReplyDeleteAndrei, I see you have a comment on Scott's blog, where you recommend tHooft's paper. Scott's gripe is that tHooft does not face the spooky implications of his superdeterministic beliefs. In spite of what you say, tHooft's latest paper has the same problem. Yes, it is "shockingly blase about the absurd implications", just as Scott says of the earlier papers.
ReplyDelete"The tHooft paper is amusing, but it is not really a scientific theory or a superdeterministic theory that makes predictions. It is just a mathematical construction to defend some philosophical stance."
ReplyDeleteThat might be so, but my point was to make clear what a superdeterministic theory intends to do. I think it is clear that 't Hooft intends to reproduce QM, not reject it. Hopefully we can agree on that.
"No, P3 does not follow, as you have explained it."
Why? What other option do you have? If there is nothing about B that determines the measurement result how can you predict that result? Pure luck? To my understanding to say that you can perfectly predict the outcome of a fundamentally random process is a contradiction. By definition, if something is random it cannot be predicted. But may be I am wrong, tell me your stance on this.
"To the extent that you and Maudlin argue for P3, you are just expressing a philosophical belief that is contrary to a century of physics."
No, both me and Maudlin agree that P3 necessarily follows from P1 and P2. It's not about belief here and if you can give me an alternative I may accept it. It's just I don't see how it is possible to predict something that it is unpredictable.
"Also, you say that the QM predictions about Bell correlations do not depend on assumptions about independence of the detectors. That is false."
If it is so you can give an example of two experiments (A and B), identically performed in every way with the exception that for the experiment A we assume that the detectors are independent and for the experiment B we assume they are not. You may choose any experiment you want. Show me at what point the independence assumption enters the calculation and what is the difference between the results QM predicts for A and B.
"Instead, the superdeterministic theory blindly declares that the experiment cannot be done."
I'm going to ask you for a reference for this assertion.
"Scott's gripe is that tHooft does not face the spooky implications of his superdeterministic beliefs."
Scott claims:
"The original papers by Gerard ‘t Hooft on “superdeterminism” were shockingly blase about the absurd implications I mentioned"
That may be true but I did not see those papers. I asked him to tell me what are those papers he is speaking about. He didn't answer yet. In time, please, if you agree with him, show me those papers!
The other alternative to P3 is QM. Bell was comparing a quantum theory to a classical theory. If you are living in 1900 and can only imagine classical theories, then it might seem that classical theories are the only possibilities. Now we know better.
ReplyDeleteIf you do a Bell test experiment, and the detectors are not independent, then the correlations could be anything. Neither QM nor any other theory can predict the outcome. So yes, experiments depend on independence assumptions.
Because superdeterminism rejects those independence assumptions, it rejects the idea that experiments can tell us anything. 'tHooft does not come to grips with this. He rejects free will, and rejects all experimental science. I don't know why he bothers trying to approximate QM, because he is rejecting all the experiments confirming QM anyway.
"The other alternative to P3 is QM."
ReplyDeleteGood luck deriving QM from P1 and P2! Hint: it cannot be done because the locality condition (P2) cannot possibly be an intrinsic property of QM (non-local variants such as Bohm's exist). So you have provided a non-answer.
There is no alternative to P3. It has nothing to do with QM or Bell. It is a pure logical problem.
"Bell was comparing a quantum theory to a classical theory."
This is both false and irrelevant to my argument.
"If you do a Bell test experiment, and the detectors are not independent, then the correlations could be anything. Neither QM nor any other theory can predict the outcome. So yes, experiments depend on independence assumptions."
Another unjustified assertion. Where exactly is this "independence assumption" present in the quantum formalism? Is it present in the Hamiltonian? Is it part of Schrodinger's equation? Does it appear in Born's rule? You need to help me here.
"Because superdeterminism rejects those independence assumptions, it rejects the idea that experiments can tell us anything."
How did you come to that conclusion? What are your premises here? How your conclusion follows?
"tHooft does not come to grips with this. He rejects free will, and rejects all experimental science."
Reference, please!
"I don't know why he bothers trying to approximate QM, because he is rejecting all the experiments confirming QM anyway."
He rejects no experiment. You just misunderstand what superdeterminism is.
You say "Good luck deriving QM". Therein lies your problem. You want to physical laws from philosophical principles. Your philosophical principles only allow classical physics. So of course you cannot derive QM.
ReplyDeleteYes, the independence assumption is necessary for the Born rule, or any other probabilistic prediction.
Here is a t Hooft paper rejecting free will. He also explains how he believes that conspiracies prevent experiments from being what they appear to be. So yes, he is rejecting experimental physics.
"You say "Good luck deriving QM". Therein lies your problem. You want to physical laws from philosophical principles. Your philosophical principles only allow classical physics. So of course you cannot derive QM."
ReplyDeleteThis is not my problem, it's your problem. You said that QM should replace P3. But P3 follows from P1 and P2. So, it's your claim that QM follows from P1 and P2. Now you say that's impossible. I agree, you just contradicted yourself.
Leaving aside the formal part of the argument it's clear that "QM" cannot be a valid answer to the question of how you can predict from B an unpredictable (random) event from A with local physics. You just avoid giving an answer.
"Yes, the independence assumption is necessary for the Born rule, or any other probabilistic prediction."
The Born rule is applied to the state. The state does not say anything about hidden variables (so it cannot depend on any assumption about them), hence Born's rule cannot depend on the assumption that the detectors and the hidden variables are independent. There is nothing stopping you taking the square of the amplitude regardless of what you believe about detectors.
"Here is a t Hooft paper rejecting free will. He also explains how he believes that conspiracies prevent experiments from being what they appear to be. So yes, he is rejecting experimental physics."
I don't see anything about any conspiracy, please quote the paragraph you have in mind!
I think that 't Hooft's view is better explained in this paper:
The Free-Will Postulate in Quantum Mechanics
https://arxiv.org/pdf/quant-ph/0701097.pdf
Sure, 't Hooft rejects free will (an experimenter's decision is determined by its past) but this is a direct implication of any deterministic theory (even without -super). There are no "true" choices in determinism, everything follows from the initial state + physical laws. In fact, Bell's theorem is logically fallacious since it assumes non-determinism (in the form of the free-will assumption) to conclude later that determinism does not work. It's just circular reasoning, no need for any theorem to prove that.
't Hooft replaces the free will assumption with another one that allows Bell's theorem to be formulated in a consistent way and still avoid the "conspiracy" argument, the " unconstrained initial state" assumption:
" In short, we must demand that our model gives credible scenarios for a universe for any choice of the initial conditions!"
So, unlike Scott claimed, 't Hooft was very concerned about the accusations against superdeterminism. And he beautifully answers them. Superdeterminism does not work by eliminating by hand the initial states that predict QM' s violations, but by showing that, regardless of the initial state, such violations cannot occur.
Nice, Scott closed the discussion about superdeterminism. He could not refute my argument, he wasn't able to quote 't Hooft making the claims he insisted 't Hooft made so he got "tired" when confronted by Steven. I'm sure the cognitive dissonance can have that effect :).
P3 depends on what you mean by "element of reality". If P3 just means that reality determines measurements, then it is a tautology. But since you explained that you mean "element of reality" to be hidden variables, then it is proven false.
ReplyDeleteYou are obviously just rejecting QM for philosophical reasons.
Yes, you can square the amplitude without knowing about the experimental setup. But to actually do the experiment, and compare the probability to the outcomes, you assume the independence of the detectors.
No, tHooft does not address any of the obvious objections to superdeterminism. In the paper you cite, he says: "We dismiss all unquestioned ‘free will’ assumptions in physics as being not worthy of a mathematically rigorous theory."
The free will assumption is needed to do an objective experiment. He is just discarding all of science as being "not worthy". He doesn't give any argument for such a radical position, other than it being contrary to his mathematical prejudices.
The 2007 paper certainly does talk about conspiracies. He says: "They howl at me that this is ‘super-determinism’, and would lead to ‘conspiracy’. Yet I see no objections against super-determinism, while ‘conspiracy’ is an ill-defined concept, which only exists in the eyes of the beholder." He later compares the conspiracy to a conservation law.
This is like a scientist being confronted with an experiment that contradicts his theory, and saying "the theory is right, but God performed a miracle to make it look wrong."
Scott did refute your argument. There is not even any scientific paper consistent with determinism.
If you still think I am wrong, then show me some published paper that relates superdeterminism to modern science. That is, one that predicts an experimental outcome, or is consistent with an experiment that has already, or somehow says something about what can or cannot happen. I say the paper does not exist. All there is junk like the tHooft papers, which say something like: "there is a theoretical possibility of superdeterminism that has not been ruled out by experiment, but which no one has a theory for, and no one knows how to test it, and no one knows what scientists would do if it were true, as it would abandon everything that has been done in the last 500 years."
ReplyDelete"If you still think I am wrong, then show me some published paper that relates superdeterminism to modern science. That is, one that predicts an experimental outcome, or is consistent with an experiment that has already, or somehow says something about what can or cannot happen. I say the paper does not exist."
ReplyDelete1. You are trying to shift the burden of proof here. The absence of evidence is not the same thing as the evidence of absence. There was a time before any theory that is accepted today was published. At that time the theory was not unscientific, it just wasn't known. If you do not know a theory you cannot conclude that the theory is wrong. This is what you are trying to sneak in here. "We don't know therefore I am right!". Logic does not work that way.
2. The prior justification for superdeterminism is extremely strong. The EPR-Bohm argument, suplemented by Bell's theorem prove that superdeterminism is the only way locality can be accommodated by the quantum framework. The argument has been properly published in a peer reviewed paper:
"What Bell did"
Tim Maudlin 2014 J. Phys. A: Math. Theor. 47 424010
https://iopscience.iop.org/article/10.1088/1751-8113/47/42/424010/meta
The paper opposes superdeterminism and promotes non-locality, but this is not important. Superdeterminism is established as the only local theory.
No other theory (except perhaps relativity, which combined mechanics with electromagnetism) had such powerful motivation. The principle of locality is widely accepted by all modern theories, hence superdeterminism is established as good science.
3. There are published papers dealing with superdeterminism directly:
Probability Theory as a Physical Theory Points to Superdeterminism
Entropy 2019, 21(9), 848
Bell’s Theorem: Two Neglected Solutions
Foundations of Physics volume 43, pages769–791(2013)
Constructing deterministic models for quantum mechanical systems
International Journal of Geometric Methods in Modern PhysicsVol. 17, No. supp01, 2040007 (2020)
Qubit exchange interactions from permutations of classical bits
International Journal of Quantum InformationVol. 17, No. 08, 1941003 (2019)
Ontological states and dynamics of discrete (pre-) quantum systems
International Journal of Quantum InformationVol. 15, No. 08, 1740013 (2017)
Are Quantum Spins but Small Perturbations of Ontological Ising Spins?
Foundations of Physics volume 50, pages1875–1893(2020)
And so on. The fact that you assert 't Hooft's model is worthless is irrelevant. You could not find any error in Maudlin's paper or in 't Hooft's papers. You just don't like them because they oppose your believes. Put your finger on those errors and we will see what is worthless or not!
4. The theory of classical electromagnetism is actually superdeterministic in the sense that Bell's independence assumption cannot be established. The polarisation of an EM wave depends on how the charge accelerates. The charge accelerates according to Lorentz' force and Newton's laws. The Lorentz force depends on the electric/magnetic fields existing at the location of the charge and those fields depend on the global charge distribution/momenta. As the detectors are part of the global charge distribution it follows that the hidden variable (polarization) is not independent from the physical states of the detectors.
There are a lot of experiments based on the classical theory of electromagnetism.
I know of no specific predictions of a superdeterministic model going beyond the standard model, but no other theory does that so I don't see how this is supposed to be evidence against superdeterminism.
1. I cannot disprove solipsism, or any other theory that denies reality. There is no example in history of anything like superdeterminism becoming accepted. Maybe many-worlds comes closest.
ReplyDelete2. Maudlin's error is that he takes Bell's theorem about local hidden variables, and omits the hidden variable hypothesis.
3. Of your papers, I looked at a couple from Vervoort: 2018 and 2012. He admits that orthodox QM, going back to Bohr, is to deny the hidden variable assumption that is so crucial Bell's work. That means that all this work is just a mathematical adventure into some hypothetical universe that has no obvious relation to our own.
It is not a matter of my beliefs. These papers are science fiction fantasies that have nothing to do with the real world. They just deny all observational knowledge, and replace it with nothing. There is no known experiment supporting anything they say.
The tHooft and Vervoort papers make it clear that their belief in superdeterminism is not based on Bell test experiments or any other experiments. It is a philosophical belief that is unrelated to the physical world. It like saying: "I believe God created the world, because who else would have done it?" There is no more substance than that.
ReplyDeleteRoger,
ReplyDeleteIt’s great that you mentioned solipsism because superdeterminism is the least solipsist-friendly view that you could find.
I’m going to focus on a paper as an example of superdeterministic model. I’ve mentioned papers by Vervoort or Maudlin to show that you can find published literature on the subject, not because I agree with everything they say. The paper I am speaking about is:
Are quantum spins but small perturbations of ontological Ising spins?
Hans-Thomas Elze, Found. Phys., 50(12), 1875-1893 (2020)
https://arxiv.org/pdf/2008.01721.pdf
The first thing that you notice about this model (which is an implementation of ‘t Hooft’s superdeterministic interpretation of QM (the cellular automaton interpretation) is that it posits a clear, objective ontology. “Reality” consists of classical Ising spins. Quantum mechanics is found to emerge from such a model due to incomplete information. There is no ambiguity in regards to what is real and what not. The incomplete knowledge would allow different observers to have different views, you will have superpositions, but it is always the case that some observers would be right and others would be wrong. The spin of a particle is either UP on X or DOWN. This eliminates the problem of solipsism. Multiple incompatible accounts (solipsistic bubbles) cannot exist in superdeterminism.
I am glad that you mentioned solipsism and I am glad you reject it. Because solipsism is what the so-called mainstream/Copenhagen interpretation leads to in a desperate attempt to avoid hidden variables. You can read solipsistic ideas between the lines when you read what Lubos Motl has to say about EPR, and you can find it in the consistent histories approach (the so-called Copenhagen done right). I will be using this paper:
EPR, Bell, and Quantum Locality
Robert B. Griffiths, Am. J. Phys. 79 (2011) 954-965
https://arxiv.org/pdf/1007.4281.pdf
To cont...
cont...
ReplyDeleteLet’s take a look at page 13, where Griffiths discusses Maudlin’s argument for non-locality. He agrees with M3:
“This means that particle b must already have been disposed to yield the opposite result even before particle a was measured.”
This resembles P3 from my argument, only he uses different words (must already have been disposed) instead of my “element of reality”. It’s the same thing. There is something “there”, an element of reality, or a predisposition that determines the measurement outcome. But M3 is even stronger than P3 because the predisposition exists even before any measurement is performed. Griffiths clearly agrees with M3:
“And M3, the disposition of the b particle to yield the opposite result even before the a particle was measured, is evident from the fact that Eqs. (33) or (37) hold for all applicable values of tj and tk: t1 and t2 before the measurement of particle a and t3 after the measurement. This disposition resides in the simple fact that the particle actually had at the earlier time the property which a measurement would later reveal. Thus far everything is fine.”
Now this looks very much like a hidden variable theory, right? The measurement results are not random, they are predetermined by the hidden variable (the predisposition). Let’s see what else we can find. Let’s first mention M4’, with which Griffiths agrees as well:
“Particle b was disposed to yield the opposite result of the measurement of particle a at all times beginning shortly after the interaction of the two particles produced the singlet state.”
And now let’s look at M5 (which is false according to Griffiths):
M5: “Therefore the complete physical description of particle b must determine how it is disposed to yield a particular outcome for each possible spin measurement”
We need to be very careful here. What Griffiths is saying is that the particle b “was disposed to yield the opposite result of the measurement of particle a” for the measurement that actually occurred, say on Z.
Proposition PG1: particle b “was disposed to yield the opposite result of the measurement of particle a” on Z.
But this is not so for other measurements, like X or Y. So, according to Griffiths, is also true that:
Proposition PG2: particle b “was NOT ALSO disposed to yield the opposite result of the measurement of particle a” on X.
What you get from PG1 and PG2 is that the particle b “knew”, from its preparation that it will be measured on Z and not on X and as a result was predisposed to give a certain result for the Z measurement, but not for the X measurement. In other words we arrived at superdeterminism. Both the hidden variable (the predisposition) and the measurement “choice” are predetermined.
OK, so “Copenhagen done right” is superdeterministic, so why this opposition against superdeterminism? Please take a look at page 5:
“Physicists are free to employ whatever framework they wish when describing a quantum system: formulas can be written down and probabilities calculated using the Sx or {x +, x−}, or the Sz framework for a spin-half particle. Call this freedom the principle of Liberty. There is no law of nature, or of quantum theory, that says that one of these is the “right” framework; from the perspective of fundamental quantum theory they are equally correct. Call this the principle of Equality”
But, how is it possible for the above to be true when we know very well that particle b was only predisposed for a Z measurement? The only possible answer is that in fact the measurement on Z is not an objective fact of the world. It is observer-dependent, just like the spin of the particles. You may recognize this view, it is called solipsism.
And this concludes my argument. You need to choose between solipsism and superdeterminism. The choice is quite easy.
The Griffiths article shows how the local hidden variable hypothesis creeps in.
ReplyDeleteM3 says "already have been disposed". This is true in the sense that the system is in a condition that allows the later measurement. But M3 stops short of saying that "disposed" means codified as a local hidden variable.
M4 says it was "disposed" earlier. This hints at determinism, but does not explicitly assert that.
M5 leaps to "the complete physical description". This more strongly suggests that there is some set of hidden variables that are somehow going to explain everything. But there is still no indication that any such description is possible.
M6 makes the leap to a deterministic hidden variable theory.
Nowhere does it explain where these hidden variables come from, or why we should assume them. They are plausible in the context of classical mechanics, but QM says that they are not possible. It is like saying:
M3 - QM might be false.
M4 - QM might have been always false.
M5 - QM is false.
You just cannot show QM is false this way. It makes no logical sense.
Here is a simpler version of your argument.
1. The QM uncertainty principle says position and momentum cannot be simultaneously measured.
2. A complete physical description of a particle would include its position and momentum.
3. Achieving that description contradicts QM experiments.
4. Those experiments could be false if a 14B year conspiracy makes them impossible.
5. QM is false.
Ultimately, all you are doing here is slipping in a local hidden variable assumption that is contrary to the letter and spirit of QM.
I agree with Blaylock's explanation as to why hidden variables are so contrary to QM.
You say: "we know very well that particle b was only predisposed for a Z measurement".
ReplyDeleteWe know no such thing. The particle could be predisposed for all sorts of measurements, depending on your determinism beliefs. The Z value might be more predictable, based on an earlier measurement.
"M3 stops short of saying that "disposed" means codified as a local hidden variable."
ReplyDeleteOK, then explain what "disposed" means.
"M4 says it was "disposed" earlier. This hints at determinism, but does not explicitly assert that."
Again, what is the difference between being disposed to give a result and being determined to give a result?
"M5 leaps to "the complete physical description". This more strongly suggests that there is some set of hidden variables that are somehow going to explain everything. But there is still no indication that any such description is possible."
The only important thing here is that Griffiths disagrees with M5. The particle is not disposed for all possible measurements.
"M6 makes the leap to a deterministic hidden variable theory."
At this point I don't care about M6. I'm not interested in Maudlin's assumptions, but in Griffiths'.
"M3 - QM might be false."
This does not follow. There is no incompatibility between QM (in its minimalist, "shut up and calculate" form and M3. If you think differently, please explain!
"You just cannot show QM is false this way. It makes no logical sense."
I do not think QM is false and I've never argued for that. In fact all my arguments are based on the assumption that QM is true.
"Here is a simpler version of your argument.
1. The QM uncertainty principle says position and momentum cannot be simultaneously measured.
2. A complete physical description of a particle would include its position and momentum."
This is a complete misunderstanding of my argument. I am only interested about what is actually measured and what can be deduced directly from that measurement. Please re-read my original argument as well as the one based on Griffiths' paper. True, the original EPR argument tryied to argue for the simultaneous existence of non-commuting properties. I did not tried to argue for that, ever. I am agnostic about position and momentum (or spins along X and Y) being simultaneously sharply defined. Such an assumption plays no role in my argument. In my discussion about Griffiths' paper I actually rely on M5 being false.
"I agree with Blaylock's explanation as to why hidden variables are so contrary to QM."
Can you point me to Blaylock's explanation?
"You say: "we know very well that particle b was only predisposed for a Z measurement".
We know no such thing. The particle could be predisposed for all sorts of measurements, depending on your determinism beliefs. The Z value might be more predictable, based on an earlier measurement."
What I said is a logical deduction based on what Griffiths says (M3 is true, M5 is false). I'm not presenting my assumptions here, I am using the assumptions made by this mainstream interpretation (consistent histories) in order to prove that hidden variables are unavoidable.
I am looking forward to see what is, in your view, the difference between predisposition and determinism. It will also be nice to reply to my argument as it was written by me, not to a different version imagined by you.
Roger,
ReplyDeleteDo you have in mind this paper by Blaylock?
The EPR paradox, Bell's inequality, and the question of locality
https://arxiv.org/pdf/0902.3827.pdf
If so, we are in agreement after all. Take a look at page 18:
"Furthermore, we should note, as did Bell,38 that the perfect correlations present in EPR experiments imply that local theories must also be deterministic. This conclusion rests on the idea that a theory with only local interactions precludes construction of the EPR correlation at a distance, and therefore the correlation must originate at a common point and propagate outward. For the perfect correlation to propagate undisturbed to separate locations, the theory must also be deterministic. Thus, taking the results of EPR and Bell experiments together, we conclude either that valid physical theories are nonlocal, or they are local, deterministic, and counterfactually indefinite."
I could not express my own position any better. I fully agree with Blaylock's conclusion above. It's only that I name those "local, deterministic, and counterfactually indefinite" theories. They are called superdeterministic.
For Blaylock, I was referring to sect. VI B of the Griffiths paper you cited. That identifies counterfactual definiteness as the crucial assumption distinguishing Bell's models from QM.
ReplyDeleteIn Blaylock's own paper that you cite, he says that the perfect correlations imply determinism. I am not sure if he means determinism in that special case, or more broadly. If he means that case, then I agree that if QM successfully predicts and outcome with 100%, then that outcome is determined.
I don't see how lesser correlations could ever be an argument for determinism.
He also says that many-worlds theory is deterministic. He is stretching the definition of determinism.
You ask how an electron can be disposed towards a particular measurement. I don't know. I do not have in my mind an intuitive model of an electron that relates it to ordinary familiar objects. Orthodox Copenhagen QM says that you are asking meaningless questions. We can predict the measurements, and explain those measurements, but we cannot say much about what the electron is doing when it is not being observed. The hidden variable advocates want to give quantitative descriptions of that observed electron, but all such attempts have failed.
So yes, we can say that an electron is disposed to a particular measurement with a particular probability, and that probability might even be 100% in some cases, but we cannot say how the electron is so disposed.
Roger,
ReplyDelete"For Blaylock, I was referring to sect. VI B of the Griffiths paper you cited. That identifies counterfactual definiteness as the crucial assumption distinguishing Bell's models from QM."
I wouldn't say that "Bell's models" are distinct from QM. Bell analyzes possible hidden variable models. They are not supposed to be an alternative for QM, but an underlying layer from which QM emerges. The purpose is to "complete" QM with additional variables in order to restore locality.
I agree with Blaylock's point about counterfactuals. Bell's theorem shows that it is not possible to ascribe hidden variables, simultaneously, for all possible measurements, as long as they are independent from the measurement settings. We know from experiments that:
1. If a is UP on X, b is DOWN on X; If a is DOWN on X, b is UP on X
2. If a is UP on Y, b is DOWN on Y; If a is DOWN on Y, b is UP on Y
3. If a is UP on Z, b is DOWN on Z; If a is DOWN on Z, b is UP on Z
What Bell needs to derive his theorem is to assume that even if you measure on X, the Y and Z spin of the particles would still be anticorrelated. But we do not have any evidence that this is the case. You CAN violate Bell's inequality if you ONLY require perfect anticorrelation when the orientation of the detectors is the same. In other words, superdeterminism allows for X-spins to be both UP if what is actually measured is the Z-spin. In this case no contradiction with experiments can be revealed.
It is worth noting however that superdeterminism does not deny counterfactual reasoning per se. A superdeterministic theory can tell you what the measurement results would be for a different choice of measurements. It's just that the hidden variables would be different for each experimental setup so you cannot assume that the results you get in one experiment remain the same in a different experiment. This is the superdeterministic equivalent of the "single framework rule" in consistent histories. The only difference is that CI insists that multiple incompatible frameworks are equally valid. Superdeterminism would say that only one "framework" (read: experimental context) is valid, the one that describes what it was measured.
" I agree that if QM successfully predicts and outcome with 100%, then that outcome is determined."
Great!
"He also says that many-worlds theory is deterministic. He is stretching the definition of determinism."
Assuming the theory works (I don't think it does) it is deterministic from a God's point of view. Everything that can happen happens, there is no uncertainty about that.
"You ask how an electron can be disposed towards a particular measurement. I don't know. I do not have in my mind an intuitive model of an electron that relates it to ordinary familiar objects."
No, this was not the intention of my question. And you answered that question by agreeing that the ability to perfectly predict the outcome implies determinism.
"The hidden variable advocates want to give quantitative descriptions of that observed electron, but all such attempts have failed."
Of course, once you accept that the ability to perfectly predict the outcome implies determinism you need to look for how this works. This is how good science works. The problem is that the mainstream disagrees that the ability to perfectly predict the outcome implies determinism so they don't see any reason to look for how it works.
Yes, Bell's models are distinct from QM. The whole purpose was to devise a model that makes a different prediction from QM, and to disprove QM. Instead, the experiments disproved Bell's models.
ReplyDeleteNo, a superdeterministic theory cannot tell us anything about a different choice of measurements. Superdeterminism denies that any such choice is possible.
No, no one disagrees with the remark that if a theory predicts an outcome with 100% certainty, then the theory is deterministic for that outcome. It is not deterministic for lesser predictions. That is just the definition of determinism -- prediction with certainty.