The quantum state cannot be interpreted statistically?

[Ken G]

They assume that the probability assignments of QM are correct, and then argue that there can't exist any additional information (in addition to the quantum state) "that is useful to predict the outcome". I don't really see how the assumption is different from what they're trying to prove.

I don't either. It shouldn't matter if QM is correct, that would be a far more stringent assumption than any PBR made. And it does sound even more circular. I'm generally not very enamored with no-go theorems in physics, the hidden assumption problem seems severe. Proofs in mathematics make sense, so if one wants to prove something within the mathematical structure that the physics borrows from, that's fine, but interpretations of the physics seem to have left that realm, and so the proper assumptions to make are much trickier.

 

[bohm2]

So I have to say, that I can’t help thinking that actually you are much closer to idealism than realism - you seem to have no "belief" that science can say anything "true" ("true" in the sense of how I would expect a philosophically aware realist to use that word) about mind independent reality. I understand (I think) what you mean when you assert you are a realist, I’m just not sure that label conforms with my understanding of what it means to be a philosophically aware realist. I know this is just abouit definitions and not substance - but I am interested how and why you may differ over my understanding of realism as it is defined in terms of philosophy.

I actually thought that KenG's position sounded very Kantian as opposed to idealism but I'm not sure? I think the only philosopher/mathematician who strongly felt that we can get "access" to the class of "true" theories (or pretty close) in some of his writings was Pierce:

In this way, general considerations concerning the universe, strictly philosophical considerations, all but demonstrate that if the universe conforms, with any approach to accuracy, to certain highly pervasive laws, and if man's mind has been developed under the influence of those laws, it is to be expected that he should have a natural light, or light of nature, or instinctive insight, or genius, tending to make him guess those laws aright, or nearly aright...This would be impossible unless the ideas that are naturally predominant in their minds was true...The history of science, especially the early history of modern science, on which I had the honor of giving some lectures in this hall some years ago, completes the proof of showing how few were the guesses that men surpassing genius had to make before they rightly guessed the laws of nature...

He repeats this when he writes:

nature fecundates the mind of man with ideas which when those ideas grow up, will resemble their father, Nature

Unfortunately, this idea has been criticized (quite convincingly, I think) by some well-known cognitive scientists/linguists.

 

[Ken G]

I think of the strict definition of realism in a philosophical sense as consisting of two parts:

1. A notion of “reality” conceived of as totally independent of our possible means of knowing it, along with the hypothesis that we do have access to the said reality, at least in the sense that we can say something “true” about it.

The first part of that is clearly realism. The second part is going too far-- it is asserting something about our relationship with what is real, but how can a true realist make an assertion like that? The true realist must accept reality completely at face value, with no preconditions at all. So I do not precondition realism with the caveat that we must be able to say something "true" about it, largely because that requires a definition of "true" that would go beyond simple realism.

Realism is an ontological stance, but characterizing what we mean by "something true" is an epistemological stance. But I don't think this is a fundamental problem, we can adopt some epistemology, like logical positivism, and call that tantamount to doing science, and then marry the epistemology with the realism and get something we might call "scientific realism" (or just logical positivism, it's more or less the same thing). The key point is, we have now gone beyond claims about what is real, and entered into a particular mode of inquiry about what is real-- leaving behind any and all "real" things that don't fit into our epistemological program.

We can not prove the hypothesis in the way that we empirically verify scientific models, so the “true” element of that statement is a philosophical statement, in the sense that it may be correct or it may not be – we will never know, all we can do is to believe in it, in the sense of having a "faith" that we can say something "true" without ever knowing that to be the case.

It seems to me that the words "faith" and the words "truth" are having a little fight in that statement, because we are trying to hold to scientific epistemology here. Outside of science, it is fine to have faith in truth, but science is all about not having faith in truth, it is all about doubting and poking and testing and questioning whatever is regarded as true. Thus I would say a "scientific truth" is like a big bullseye with a sign "give it your best shot." There's no denial of the usefulness of the provisional truth represented there, if it were not useful then science would not be useful. But there isn't much need for faith in it-- the usefulness is demonstrable, the rest is to be doubted and attacked.

2. A representation of mind independent reality worked out from the phenomena, i.e. from human experience. This representation, in science, is constructed without any need to include mind independent realty as a necessary ingredient in this process of representation.

I agree that's a necessary ingredient of doing science, but I don't think it needs to be associated with realism. Even an idealist would wish to create such representations, and a realist who rejects the value of science might not see any value in these representations. But realism is certainly consistent with doing science, and in practice all scientists I know are also realists.

The representation is used to impart the something “true” about mind independent reality, but the “true” element is a philosophical statement, again in the sense that it may be correct or it may not be – we will never know.

To me, that version of "truth" doesn't mean anything other than "usefulness." So I don't even use the word "true", just "useful." This leaves open the question "but why is it useful", but to me that's a fine question to leave open-- it's certainly not an improvement to say "it works because it's true, and the reason I claim it's true is that it works."

So a realist (of any of the usual flavours) to my mind would, firstly admit that the notion is a philosophical one, but secondly “believe” that the notion is correct, though it can’t be proven.

Yes, but here the "notion" is that there is something real, it does not include any of the aspects that we are attributing to reality. Attributing aspects to reality is a provisional, contextual, and goal-oriented process, all part of the "representations" but not part of the "reality." The map is not the territory.

Now you seem to be saying that one can be a realist without adopting a “belief” that the said realist can say something "true" about mind independent reality.

Correct, because the word "true" in that sentence does not mean anything demonstrably more than "useful" or "expedient." So given that, we should just say "one cannot be a scientist without adopting the belief that the realist can say something useful or expedient about mind independent reality," and note that this is actually not a "belief", it is pretty demonstrably correct (cures to disease, use of technology, etc.).

I’m just, how shall I say, uneasy over your definition. I’m not saying its wrong; it just seems different to how I understand realism. As best as I can infer, you would say that the properties of physics are a useful means in which to do physics rather than implying that those properties are a “true” (“true” in the sense in which I would expect a philosophically aware realist to use the term) representation of mind independent reality.

Right. Your use of what a realist would regard as true sounds an awful lot like what Jaynes called the mind projection fallacy.

I would say that you make no reference at all to mind independent reality in terms of these properties – you don’t see it as any issue.

Yes, I see the use of properties as having nothing to do with realism. An idealist could make just as good use of the concept of properties as a realist could, indeed the idealist is the one who needn't fear the mind projection fallacy, because it isn't a fallacy for them.

Now actually I agree with that, but I would never think of myself as a realist, I would say I am much closer to idealism. I do believe (strongly) that there “exists” a mind independent reality, but equally strongly, I can’t see how we are ever going to penetrate this reality through science.

It depends on what you mean by "penetratre". I think that as soon as you say you believe (strongly) in mind independent reality, you are not an idealist, you are a realist. To say you don't think we can "penetrate" that reality doesn't make you not a realist if by "penetrate" you mean "understand the actual truth of." If you just mean "gain useful conceptual understanding and practical power over", then we clearly do "penetrate" that reality to some degree using science.

So whilst I consider that I adopt a stance of idealism, it is not radical idealism, I do actually consider that our reality “emerges” (and I use the word "emerge" here in no way to impart any kind of familiar usage, I just can't think of any other way to say it) in some manner from mind independent reality and that that "emergence" gives rise (in an undefined manner) to the consistencies inherent within our reality, but I have no realist “belief” that we can say something “true” about that mind independent reality (or the "emergence" to our reality) using science.

Then what I am saying is, you are the actual realist here, and those who claim that science can say something absolutely true about reality (not provisionally true, not effectively true, not borrowed from some formal pattern or mathematical structure in which that element actually has its existence), are not realists because their position is fundamentally logically inconsistent. They are committing the mind projection fallacy, which is only a fallacy for realists! So ironically, their position is only internally consistent if they are idealists (and only if they drop the "mind independent" part).

I don’t think there is any justification to believe that what exists outside of our reality is of a form that we would recognise in any manner, thus I can't take on board the "belief" that the realist has in thinking that we can say something true about mind independent reality in terms of science.

I agree, that's why such self-styled "realists" are not being very realistic.

So I have to say, that I can’t help thinking that actually you are much closer to idealism than realism - you seem to have no "belief" that science can say anything "true" ("true" in the sense of how I would expect a philosophically aware realist to use that word) about mind independent reality.

To summarize, I claim that what makes my stance consistent with realism is that we need to substitute the words "useful and expedient" where you have "true", and if we do that, I not only do have that "belief", I claim it is not a belief at all-- it is fully substantiated by fact.

 

[Ken G]

I actually thought that KenG's position sounded very Kantian as opposed to idealism but I'm not sure? I think the only philosopher/mathematician who strongly felt that we can get "access" to the class of "true" theories (or pretty close) in some of his writings was Pierce:

Yes, I think that's accurate, and I agree with the critics of Pierce. I don't think the arguments "it has to be true or it wouldn't work so well" and "it has to be true or we couldn't have evolved to come up with it" just don't hold any traction. We know things that aren't really true work very well all the time, and we can't claim that everything our mind does must be true or we couldn't have evolved to do it because our minds are capable of logical gaffes. Finally, we can't say that although many things that work aren't true, and although our minds are capable of complete gibberish, all the same the things that work best must be true, and in and amongst all that gibberish must be the actual truth. I can't see any logical requirement for that argument to hold, it sounds much more like wishful thinking to me.

It should be said that I interpret those remarks by Pierce as just a brand of idle speculation on his part-- he was a consummate logician and he perfectly well understood the role of symbols and metaphors in language, so I don't think he would have seen anything in that argument as logically rigorous. He was trying to address the question, why do physics theories work so well, and for that question his answer is perfectly adequate. However, it is not any kind of answer to the question, "is physics true", because if one holds that only what is true could work, one is making an argument that is not only circular, its assumptions run afoul of millennia of evidence to the contrary.

 

[bohm2]

I just do not understand how there can be so many interpretations of PBR? Here's a FQXi BLOG that just came out:

Let me try to summarise their argument. They suppose a particular kind of PSI-epistemic model is possible and then show a contradiction with quantum statistics. The kind of model they consider is essentially a hidden-variable one. The idea is that at the time of preparation of a quantum system one also sets the value of some hidden variable Lambda...

This is *not* assumed to be local as far as I can tell. Lambda is assumed to determine the probabilities of different outcomes. But, also for the sake of argument, Lambda is assumed not to uniquely determine the quantum state, i.e. the same value of Lambda can be associated with the preparation of several different quantum states. So the argument, modulo potential subtleties like hidden assumptions, puts another nail in the coffin for hidden variable theories, adding to the contributions by Bell and others. As it is quite clean and does not appear to assume the hidden variable is local, one can imagine it turning up in text-books at some point.

A very interesting paper by Colbeck and Renner has just appeared apparently deriving a very similar result from even more minimal assumptions, and I know that at least one more related paper will appear on the arXiv soon. My personal inclination remains to not think of the wave-function as a real object.

Are we getting closer to nailing down what the wavefunction is?
http://www.fqxi.org/community/forum/topic/999

 

[Fredrik]

I just do not understand how there can be so many interpretations of PBR?

I think the main reason is that the PBR article is so badly written. They haven't clearly separated the mathematical stuff from the non-mathematical, and the mathematical theorem isn't clearly stated anywhere in the text. The proof doesn't explain what assumptions they're using when they're using them.

Here's a FQXi BLOG that just came out:

Are we getting closer to nailing down what the wavefunction is?
http://www.fqxi.org/community/forum/topic/999

This guy says that the theorem doesn't assume locality. The assumption that Michael Hall (the guy who wrote the article Demystifier linked to) called "factorisability" looks like a locality assumption to me. On the other hand, Hall says that he can weaken that assumption and still get the same conclusion. I haven't studied the details of Hall's article.

Edit: In my post #155, the factorisability assumption looked like this:

We assume that
$$Q_{\psi\psi'}(\lambda,\lambda') =Q_\psi(\lambda)Q_{\psi'}(\lambda')$$ for all values of the relevant variables.

 

[Ken G]

What's more, I got the impression that the PBR proof held no sway over deBroglie-Bohm, which is by far the dominant hidden variables theory. Yet this new blog entry seems to take aim directly at deBroglie-Bohm. Why would PBR not directly mention deBroglie-Bohm if they were finding some inconsistency in it? So which is it-- does PBR claim to rule out deBroglie-Bohm, or doesn't it? And if it doesn't, how is that a "nail in the coffin of hidden variables theories"?

 

[Fredrik]

I think it's clear that PBR doesn't rule out de Broglie-Bohm. Harrigan & Spekkens explains that dBB is a ψ-supplemented (and therefore not ψ-epistemic) ontological model for QM. PBR only rules out (local?) ψ-epistemic ontological models.

 

[Ken G]

OK, that's what I thought, but note deBroglie-Bohm is the quintessential nonlocal hidden variables theory that gives the same results as quantum mechanical states. So if that latest blog thinks PBR extends generally to nonlocal hidden variables theories, it would be strange to call that a nail in their coffin when deBroglie-Bohm is alive and kicking. Reports of the demise of hidden variables seem greatly exaggerated! (My own objection to hidden variables theories is that we don't build theories to hide our variables, we build theories that include perfectly apparent variables to explain some observations that previous theories, with their own perfectly apparent variables, don't.)

 

[bohm2]

My head is spinning. Valentini, who is a big-time supporter of deBroglie-Bohmian interpretation seems to be very excited about this theorem. This suggests to me that he feels it rules out some other interpretations as suggested also in the Leifer piece. I'm kind of looking forward to see what the major Bohmian group of Durr/Goldstein/Tumulka/Zanghi have to say about PBR but I haven't come across anything, yet. Either way, I'm totally lost but then again, the experts themselves don't seem to be doing much better?

 

[my_wan]

I'll try again to contextualize these characterizations of what the PBR theorem entails. Consider what Matt Leifer said:

The question is whether a scientific realist can interpret the quantum state as an epistemic state (state of knowledge) or whether it must be an ontic state (state of reality).

This is the defining feature where the propensity is for people to separate epistemic and ontic states into mutually exclusive categories. Here is what Matt Leifer said immediately following the above statement:

It[/PLAIN] seems to show that only the ontic interpretation is viable, but, in my view, this is a bit too quick.

This I hope to justify in a historical context. He then follows that with the statement:

On careful analysis, it does not really rule out any of the positions that are advocated by contemporary researchers in quantum foundations. However, it does answer an important question that was previously open, and confirms an intuition that many of us already held.

Why then is the PBR theorem so important if it fails to rule out any of the positions that are advocated by contemporary researchers? Exactly as Matt said: It formally closes a potential hole that was previously merely assumed to be closed by the researchers in the field. Now it's time to contextualize the epistemic verses ontic characterizations in a historical context, to show why neither the ontic or epistemic positions advocated by modern researchers have not been ruled out.

Historically classical thermodynamics (CT) was developed first and was a purely epistemic construct. It made no reference to any underlying ontic constructs whatsoever. This ignited a debate quiet similar to the ontic verses epistemic debate today. Then over some years statistical mechanics (SM) was developed. Although SM made use of statistics it explicitly defined precisely what bits of mechanistic data were traded in the ensemble procedure. The epistemicists of the time still felt safe. After all the ontologist couldn't prove their atoms existed, they merely had an equivalent theoretical construct. That is until Einstein published his work on Brownian motion, which provided an empirical distinction between CT and SM and proved atoms existed. At least existed as something more than a mathematical fiction, whatever that something was. Ironically it was Einstein's logical positivist approach to relativity that drove the more modern developments, which put ontic based dynamics in the back seat.

The question this historical bit posses is: Did the ontic formalization SM remove the epistemic content of either CT or SM? Absolutely not, in either case. Both such models are explicitly formulated in terms of "states of knowledge", i.e., epistemic. The value and contributions of epistemicists will not go away under any circumstances, but it is not exclusive of the potential value ontologist provide. Such as SM and the empirical consequences provided through Brownian motion. The PBR theorem did not invalidate epistemic models any more than SM invalidated the epistemic content of both SM and CT. It did however open up the possibility of contextualizing QM in terms of variables that are not fundamentally statistical, whether those variables have epistemic or ontic substructures in themselves or not.

Now before anybody tries to make too big a deal out of this analogy to classical physics, it is interesting to note what set QM apart. The notion that QM can be derived from known positions and momentums of parts is completely and irrevocably broke. Will not even waste my time with anybody arguing otherwise. Yet it seems to me that given only what we know from classical physics alone it must be broken, not necessarily that it entails QM. The reason fundamentally harks back to the complaints of Newton's critiques, especially wrt gravity, but also the magic like properties sprinkled on classical particles. With SR we could easily interpret the effects as kinematically induced illusions in an otherwise Newtonian flat spacetime metric. A few paradoxes, if viewed this way along ontic assumptions, notwithstanding. With GR it becomes explicitly dynamic, breaking this kinematic illusion interpretation if ontic assumptions are involved at any level. Any ontic based construct must then also be able to generate differing relativist metrics of space and time. IIf any sort of mechanistic dynamics generates empirical metrics of space and time upon which positions are given empirical meaning, what then can we say about the positions of things at a level below which relativistic positions are even defined or definable? No more than we can say about a position outside the Universe. Hence, given the assumption of any form of ontic substructure, the very foundation of upon which SM rest, the positions and momentum of particles, is ripped out from under classical physics prior to any QM considerations. Yet this position/momentum model is the prototype by which the strangeness of QM is judged. This to me is ironic.

 

[Fredrik]

My head is spinning. Valentini, who is a big-time supporter of deBroglie-Bohmian interpretation seems to be very excited about this theorem. This suggests to me that he feels it rules out some other interpretations as suggested also in the Leifer piece. I'm kind of looking forward to see what the major Bohmian group of Durr/Goldstein/Tumulka/Zanghi have to say about PBR but I haven't come across anything, yet. Either way, I'm totally lost but then again, the experts themselves don't seem to be doing much better?

My head is spinning too, but I'm not looking forward to more opinions and interpretations from the experts. The only thing I would be interested in at this point is a much more rigorous proof of the mathematical part. I don't know how many times I've read the "simplified" argument, and I still don't know what the **** they're talking about. I don't even know what the theorem says. (Not exactly). It looks like the "simplified" argument should prove something like this:

No quantum theory with a 2-dimensional Hilbert space has a ψ-epistemic ontological model such that for some orthonormal basis {|0>,|1>}, the probability distributions of ontic states corresponding to |0> and (|0>+|1>)/√2 are overlapping.​

But my best guess at what the proof is really saying goes like this:

Suppose that the above is false. Define the quantum theory of two non-interacting qubits. Pull an ontological model for it out of a hat. Use an assumption/theorem that looks suspiciously like locality. Yada-yada-yada contradiction.​

I don't know why there would even exist an ontological model for the two-qubit theory. Maybe it can be derived from the ontological model for the single-qubit theory, by arguments similar to the ones in Aerts & Daubechies, but I'm not sure, and in either case, it's a very non-trivial detail. A proof must explain if it's an additional assumption, or if they're just using another theorem there.

The "factorisability" is another interesting issue. It looks like locality to me, but no one seems to call it that.

 

[my_wan]

Here is simplest toy model I can think of to contextualize the PBR results in an ontic construct. Following the procedure outlined by PBR we begin by preparing four systems with four states. These states are prepared such that state 1 never has property 1, state 2 never has property 2, etc. All four can have 3 of the four properties mentioned. Now if $\Lambda\neq\Lambda_1$ the probability of measuring one of the four properties is certain. Only QM dictates that the outcome will never result in any of the four properties.

In fact, as far as I see, all such no-go theorems are predicated on a first order logic, $\Lambda=\Lambda_1$, in relating measured variables to onic objects. That's why they are limited to non-contextual assumptions. Let's look at the two logical structures more closely.

First-order logic:
To illustrate visually why, consider a 3 sided dice. The dice 1 is labeled: [1,2,3], dice 2: [1,2,4], dice 3: [1,3,4], and dice 4: [2,3,4]. Hence each dice has a zero probability of landing on one of the four possible numbers. Yet given a random one of the four dice it must land on one of the four numbers. Only QM says, in terms of ψ, it cannot land on any of the four numbers.

Higher-order logic:
So let's try a different classical state variable, temperature. We don't even need four states but we will prepare four systems. Each mixture has equal probability of possessing three of four possible states, zero probability of one unique state (or temperature). Now to randomize these four systems requires mixing them in the measuring process, though they were prepared separately. QM requires that in order to randomize or entangle (not know which state is being measured) they must be mixed like the dice before being measured, irrespective of being prepared separately. If you measure each state separately in a separate measuring device then the QM makes an entirely different prediction. It is now trivial to define four states (temperatures) in which the mixed state can never result in any of the four prepared states. In QM terms the properties are entangled.

This last analogy is why the Bohmian's are so exited. The dice analogy is the naive mechanistic view that Matt Leifer said: "On careful analysis, it does not really rule out any of the positions that are advocated by contemporary researchers in quantum foundations." This includes those assuming ψ has some ontic substructure, like the medium with a temperature state variable, and the purely epistemic constructs.

 

[DevilsAvocado]

... PBR only rules out (local?) ψ-epistemic ontological models.

Nope, any ontological model must be non-local within the standard Bell framework.

 

[DevilsAvocado]

Regarding dBB: Unless the Pilot Wave is ψ-ontological de Bohemians are in trouble (according to Leifer’s own conclusion). Is the Pilot Wave real?

 

[Fredrik]

Nope, any ontological model must be non-local within the standard Bell framework.

I'm not sure that's accurate. I think Bell's theorem only rules out those local ontological models for QM that assign probabilities 0 and 1 to measurement results. I don't think it applies to models that can assign any number in [0,1]. Do you have some other theorem in mind?

Even if your statement is correct, that doesn't automatically mean that the word "local" shouldn't be there (in my statement about what the PBR theorem says). It only means that if it should, then the theorem doesn't prove anything we didn't know already.

 

[DevilsAvocado]

I'm not sure that's accurate. I think Bell's theorem only rules out those local ontological models for QM that assign probabilities 0 and 1 to measurement results. I don't think it applies to models that can assign any number in [0,1]. Do you have some other theorem in mind?

Even if your statement is correct, that doesn't automatically mean that the word "local" shouldn't be there (in my statement about what the PBR theorem says). It only means that if it should, then the theorem doesn't prove anything we didn't know already.

I don’t agree. Any pre-assignment, not matter which form, needs non-locality.

Why!?

Because if the EPRB experiment is done properly A and B should be outside each other’s light cone when the randomly rotating polarizer stops.

You could pre-assign all numbers in the world and still it won’t help, because it’s the relative angle between A and B that is crucial.

 

[Ken G]

IIf any sort of mechanistic dynamics generates empirical metrics of space and time upon which positions are given empirical meaning, what then can we say about the positions of things at a level below which relativistic positions are even defined or definable? No more than we can say about a position outside the Universe. Hence, given the assumption of any form of ontic substructure, the very foundation of upon which SM rest, the positions and momentum of particles, is ripped out from under classical physics prior to any QM considerations. Yet this position/momentum model is the prototype by which the strangeness of QM is judged. This to me is ironic.

I think this places us back into the context where we agree. I have been saying all along that ontic substructures, like the concept of exact position and momentum (often claimed to be an ontic substructure of classical mechanics, but I maintain it was never that at all, just a kind of lazy fiction that makes it easier to talk about classical mechanical predictions but is in no way central to those predictions and certainly was never a tested aspect of the theory), are always provisional and contextual. No theory ever required them, there is no such thing as a theory that is "founded on" such substructures, for the simple reason that all theories have to work in concert with how scientists actually do science. So the irony that you see in calling quantum mechanics "unreal" if it doesn't preserve the single most unrealistic, unnecessary, and undemonstrated element of how classical mechanics actually connects with the performance of physics, is the irony I see in claiming that quantum mechanics "realists" must believe in "a complete set of properties" that determine outcomes. That is a highly unrealistic assumption in my view, so what I have been trying to say is, we should not make the mistake of equating ontological descriptions with realist descriptions, when being realist should mean, above all, recognizing the limitations of ontological language about reality. The only people who can believe that their ontological descriptions are absolute truth about reality must be idealists, which is the opposite of realism. (That is also why I claimed that Brownian motion does not prove that atoms exist, it merely adjudicates in favor of the benefits of borrowing the atomist ontology from the mathematical structures in which atoms actually do exist.)

 

[my_wan]

I'm not sure that's accurate. I think Bell's theorem only rules out those local ontological models for QM that assign probabilities 0 and 1 to measurement results. I don't think it applies to models that can assign any number in [0,1]. Do you have some other theorem in mind?

Even if your statement is correct, that doesn't automatically mean that the word "local" shouldn't be there (in my statement about what the PBR theorem says). It only means that if it should, then the theorem doesn't prove anything we didn't know already.

(My bold)

This is how I see it more or less. More or less the point I was making with first-order verses higher-order logic. The [0,1] or law of the excluded middle models only appear to make sense if you are looking for particles that "own" properties like raisins in pudding. Once you allow two bowls of pudding to mix all bets are off as to which pudding the raisins belong to, or even whether the raisins will stay intact.

 

[Fredrik]

I don’t agree. Any pre-assignment, not matter which form, needs non-locality.

Why!?

Because if the EPRB experiment is done properly A and B should be outside each other’s light cone when the randomly rotating polarizer stops.

You could pre-assign all numbers in the world and still it won’t help, because it’s the relative angle between A and B that is crucial.

OK, that makes sense.

 

[DevilsAvocado]

(My bold)

This is how I see it more or less. More or less the point I was making with first-order verses higher-order logic. The [0,1] or law of the excluded middle models only appear to make sense if you are looking for particles that "own" properties like raisins in pudding. Once you allow two bowls of pudding to mix all bets are off as to which pudding the raisins belong to, or even whether the raisins will stay intact.

my_wan, I respect your knowledge, but this is really so simple that a 10-year-old can understand, if explained. (That’s why I understand! )

No tornado, raisins, pudding or middle models in the world could save your a**, it just doesn’t work.

The only way, is to refute empirical data and blame on loopholes, and I know you’re too smart for that. This is the simplest form of Bell's inequality:

N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°)​

And we could simplify it even more and say that Local Realism result in this:

1 + 1 = 2​

And QM theory + all EPR-Bell experiments performed this far result in this:

1 + 1 = 3​

No raisins in the world could ever get you out of this, trust me buddy!

 

[DevilsAvocado]

OK, that makes sense.

Okay

 

[Ken G]

I do think the PBR theorem considers an "ontological model" to be one that can be conceived as producing only probabilities of 0 or 1, that must be what they mean by the outcome being determined by a complete set of properties. If they say the complete set of properties only sets the probabilities, how is that a complete ontological description? Where is the "random number generator" in that ontology?

 

[apeiron]

(My bold)

This is how I see it more or less. More or less the point I was making with first-order verses higher-order logic. The [0,1] or law of the excluded middle models only appear to make sense if you are looking for particles that "own" properties like raisins in pudding. Once you allow two bowls of pudding to mix all bets are off as to which pudding the raisins belong to, or even whether the raisins will stay intact.

A more accurate analogy could be two vortices mixing. The "raisins" are contextual, the product of boundary constraints..

A couple of simulations of vortex merging...





Also, real life storms...

http://en.wikipedia.org/wiki/Fujiwhara_effect

 

[DevilsAvocado]

I do think the PBR theorem considers an "ontological model" to be one that can be conceived as producing only probabilities of 0 or 1, that must be what they mean by the outcome being determined by a complete set of properties. If they say the complete set of properties only sets the probabilities, how is that a complete ontological description? Where is the "random number generator" in that ontology?

I don’t understand the PBR theorem completely, but I can tell you that if you are going to discuss any "underlying ontic state" you need to take Bell in consideration.

 

[DevilsAvocado]

A more accurate analogy could be two vortices mixing. The "raisins" are contextual, the product of boundary constraints..

A couple of simulations of vortex merging...





Also, real life storms...

http://en.wikipedia.org/wiki/Fujiwhara_effect

Looks nice apeiron but even with these 'particles' outside each other’s light cone, gravity or whatever, is always ≤ c therefore this won’t help.

 

[my_wan]

I think this places us back into the context where we agree. I have been saying all along that ontic substructures, like the concept of exact position and momentum (often claimed to be an ontic substructure of classical mechanics, but I maintain it was never that at all, just a kind of lazy fiction that makes it easier to talk about classical mechanical predictions but is in no way central to those predictions and certainly was never a tested aspect of the theory), are always provisional and contextual. No theory ever required them, there is no such thing as a theory that is "founded on" such substructures, for the simple reason that all theories have to work in concert with how scientists actually do science. So the irony that you see in calling quantum mechanics "unreal" if it doesn't preserve the single most unrealistic, unnecessary, and undemonstrated element of how classical mechanics is often described, is the irony I see in claiming that quantum mechanics "realists" must believe in "a complete set of properties" that determine outcomes. That is a highly unrealistic assumption in my view, so what I have been trying to say is, we should not make the mistake of equating ontological descriptions with realist descriptions, when being realist should mean recognizing the limitations of ontological language about reality.

In our debate I was explicitly singling out our differences. My level of agreement with you has not diminished in the course of the debate.

We absolutely know, even without QM or the classical thermodynamics verses statistical mechanics analogy, that position is purely contextual. We even new it in terms of Galilean relativity in Newton's time. It's the main motivation behind a very fundamental principle called coordinate or background independence. Hence a coordinate choice is by definition not a physical choice. Relativity merely articulated how these contextual variables are related. Even on the face a velocity can be both zero and nonzero at the same time, depending on the nonphysical coordinate choice chosen.

The main point is that these contextual variables do not rule out ontic constructs in which we are then free to contextualize in a bewildering number of coordinate choices or spaces. Yet all valid choices transform into one another in one way or the other, no matter how different they appear on the surface or involve apparently incongruent definitions in one coordinate choice as opposed to another. To many ontic realist this is precisely because a nonphysical coordinate choice is merely an invention for contextualizing a common underlying ontic state. Even the apparent degrees of freedom can vary as a result of coordinate choice. Yet any valid model involving any coordinate choice still must transform via symmetries into each other, because the ontic system is the same system and is doing nothing different as a result of our coordinate choice. Epistemicists have their own varying ways of conceptualizing this commonality, which is no less empirically valid.

We even have coordinate independent mathematical formulations to explicitly recognize this fact. I'll even go a step farther and say, in my opinion, that philosophical stances, so long as they are not at odds with the underlying facts of the system, are equivalent to a nonphysical coordinate choice. No matter how diametrically opposed two philosophical stances appear on the surface. The best psychological profiles even explicitly treat it as a coordinate space.

So a coordinate choice by definition defines the coordinate space as nonphysical, while whatever it is that defines the commonalities that allows one to be transformed into the other is the reality. If you think of a model strictly in terms of the coordinate choice used to define it, and the apparent definitions that particular choice entails, then of course the only sane perspective to take is a purely epistemic one.

 

[apeiron]

Looks nice apeiron but even with these 'particles' outside each other’s light cone, gravity or whatever, is always ≤ c therefore this won’t help.

I don't get what you mean about the particles being outside any light cones in this intuition-priming example. If the two vortices are in fact interacting - via a merger of their boundary constraints, or "wavefunction entanglement" - then what are you talking about here?

 

[my_wan]

A more accurate analogy could be two vortices mixing. The "raisins" are contextual, the product of boundary constraints..

A couple of simulations of vortex merging...





Also, real life storms...

http://en.wikipedia.org/wiki/Fujiwhara_effect

Looks nice apeiron but even with these 'particles' outside each other’s light cone, gravity or whatever, is always ≤ c therefore this won’t help.

@apeiron
Nice. The raisin pudding was a tongue in cheek analogy. I used hurricanes previously but shied away from including hurricane interactions, though it makes as good an analogy. Just be careful that you are clear on the limitations of these classical analogies. They are limited in more ways just EPR.

@DevilsAvocado
Yes, information is limited to c, but only if you assume a fundamental ontic particle is required to carry directly accessible empirical information is this a problem. If a particle lacks any dynamics to store information then it carries no information. If it is not presently interacting with the Universe, position doesn't even have meaning outside it's relation to the Universe, then it carries no information. If those hurricanes are the particles, how are the hurricanes to send and receive information faster than the speed of sound? They can't. Certainly the speed of sound changes under different conditions, but only because there is a preexisting spacetime metric, defined by relativity, to provide a reference to measure it against. That doesn't limit the air molecules to the speed of sound. Very important fact about GR and c, under GR the speed c is a relativistic constant, not an absolute constant. Big distinction.

 

[DevilsAvocado]

I don't get what you mean about the particles being outside any light cones in this intuition-priming example. If the two vortices are in fact interacting - via a merger of their boundary constraints, or "wavefunction entanglement" - then what are you talking about here?

Probably some misunderstanding, let me give you the 'complete chain':

... PBR only rules out (local?) ψ-epistemic ontological models.

Nope, any ontological model must be non-local within the standard Bell framework.

I'm not sure that's accurate. I think Bell's theorem only rules out those local ontological models for QM that assign probabilities 0 and 1 to measurement results. I don't think it applies to models that can assign any number in [0,1]. Do you have some other theorem in mind?

Even if your statement is correct, that doesn't automatically mean that the word "local" shouldn't be there (in my statement about what the PBR theorem says). It only means that if it should, then the theorem doesn't prove anything we didn't know already.

I don’t agree. Any pre-assignment, not matter which form, needs non-locality.

Why!?

Because if the EPRB experiment is done properly A and B should be outside each other’s light cone when the randomly rotating polarizer stops.

You could pre-assign all numbers in the world and still it won’t help, because it’s the relative angle between A and B that is crucial.

I'm not sure that's accurate. I think Bell's theorem only rules out those local ontological models for QM that assign probabilities 0 and 1 to measurement results. I don't think it applies to models that can assign any number in [0,1]. Do you have some other theorem in mind?

Even if your statement is correct, that doesn't automatically mean that the word "local" shouldn't be there (in my statement about what the PBR theorem says). It only means that if it should, then the theorem doesn't prove anything we didn't know already.

(My bold)

This is how I see it more or less. More or less the point I was making with first-order verses higher-order logic. The [0,1] or law of the excluded middle models only appear to make sense if you are looking for particles that "own" properties like raisins in pudding. Once you allow two bowls of pudding to mix all bets are off as to which pudding the raisins belong to, or even whether the raisins will stay intact.

my_wan, I respect your knowledge, but this is really so simple that a 10-year-old can understand, if explained. (That’s why I understand! )

No tornado, raisins, pudding or middle models in the world could save your a**, it just doesn’t work.

The only way, is to refute empirical data and blame on loopholes, and I know you’re too smart for that. This is the simplest form of Bell's inequality:

N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°)​

And we could simplify it even more and say that Local Realism result in this:

1 + 1 = 2​

And QM theory + all EPR-Bell experiments performed this far result in this:

1 + 1 = 3​

No raisins in the world could ever get you out of this, trust me buddy!

To me it looked like my_wan was trying to refute Bell's inequality and EPR-Bell experiments with "raisins in pudding" and that’s what I replied on.

If you and my_wan are talking about something else, I apologize.

 

[my_wan]

To me it looked like my_wan was trying to refute Bell's inequality and EPR-Bell experiments with "raisins in pudding" and that’s what I replied on.

If you and my_wan are talking about something else, I apologize.

No, it in no way refutes Bell's inequality. It merely states the limits of what Bell's theorem can demonstrably rule out. Bell's theorem has essentially the same limits as the PBR theorem in terms of it's use of first-order logic in assigning properties to particles.

 

[my_wan]

Think of it this way. EPR proves A which implies, but does not prove, B. Nobody has definitively proved B is not a valid consequence of A. Hence EPR proves B.

Do you see the logical error there in the last sentence alone? That is the error often used in overstating the claims of what Bell's theorem did in fact prove.

 

[DevilsAvocado]

@DevilsAvocado
Yes, information is limited to c, but only if you assume a fundamental ontic particle is required to carry directly accessible empirical information is this a problem. If a particle lacks any dynamics to store information then it carries no information. If it is not presently interacting with the Universe, position doesn't even have meaning outside it's relation to the Universe, then it carries no information. If those hurricanes are the particles, how are the hurricanes to send and receive information faster than the speed of sound? They can't. Certainly the speed of sound changes under different conditions, but only because there is a preexisting spacetime metric, defined by relativity, to provide a reference to measure it against. That doesn't limit the air molecules to the speed of sound. Very important fact about GR and c, under GR the speed c is a relativistic constant, not an absolute constant. Big distinction.

my_wan, I’ve become a "Fifth Columnist" when it comes to EPR-Bell nowadays – I’m a believer!

Seriously, if you run a "standard universe" it doesn’t matter what you do or not do before the measurement (I was unclear in last post, sorry), as long as you say "Nope! I’m not going to use non-locality to solve this mess!", then you’re in deep trouble, i.e. assuming a 'standard' universe.

Now, if you could cope with an 'exotic' universe, like non-reality (aka non-separable), or something "outside it's relation to the Universe", or just plain MWI (last unclear also here, sorry), then you can make it.

But personally, I don’t see how this is ever going to save good old "Joe Six-pack" Local Realism... you substitute non-locality for some other 'weird stuff', and this will make Joe mad anyway... no?

 

[DevilsAvocado]

No, it in no way refutes Bell's inequality. It merely states the limits of what Bell's theorem can demonstrably rule out. Bell's theorem has essentially the same limits as the PBR theorem in terms of it's use of first-order logic in assigning properties to particles.

Okay, personally I think it’s 99% clear that Local Realism is not compatible with QM predictions or EPR-Bell experiments.

 

[DevilsAvocado]

Think of it this way. EPR proves A which implies, but does not prove, B. Nobody has definitively proved B is not a valid consequence of A. Hence EPR proves B.

Do you see the logical error there in the last sentence alone? That is the error often used in overstating the claims of what Bell's theorem did in fact prove.

Again, it’s so simple that a 10-year-old can understand. This is what it’s all about:

N(+30°, -30°) ≤ N(+30°, 0°) + N(0°, -30°)​

Personally, I don’t see the use of logical validation in this case, it’s basically first grade math we are talking about, 1 + 1 = 2. And in worst case, you might not see the forest for the trees:

All cups are green.
Socrates is a cup.
Therefore, Socrates is green.​