ThomasT said:
Ok. But quantum nonlocality refers to logical rather than physical connections, and is just one of many misnomers that have become defacto standards in the literature.
This is just a result of the experimental designs necessary to produce entanglement. No instantaneous physical connection between A and B is implied. Quantum nonlocality is acausal.
etc..
ThomasT,
So you're a fundamentalist instrumentalist (far too many syllables for a job description).
A standard reference such as the Stanford Encyclopedia of Philosophy article on "http://plato.stanford.edu/entries/qm-action-distance"" dismisses your argument in three of its several thousand lines:
"
Orthodox QM is a good instrument for predictions rather than a fundamental theory of the physical nature of the universe. On this instrumental interpretation, the predictions of QM are not an adequate basis for any conclusion about non-locality: the theory is just an incredible oracle (or a crystal ball), which provides a very successful algorithm for predicting measurement outcomes and their probabilities. It offers little information about ontological matters, such as the nature of objects, properties and causation in the quantum realm."
So I fail to see why you are using the instrumentalist Orthodox interpretation of QM to make sweeping statements about the physical reality of 'action at a distance', and to justify writing 'Incorrect. Incorrect.' next to perfectly correct statements of fact in my original post #36.
Having just read the above article it pretty much agrees with my post but does a much better job of it as you might expect from an Encyclopedia article (though I note it doesn't appear to use many-worlds as a get-out clause, as I do, just many-minds, and adds a minor interest get-out clause about the definition of causation, which it then proceeds to dismiss).
See also Maudlin's excellent "
https://www.amazon.com/dp/0631232214/?tag=pfamazon01-20" book which comes to the same conclusions:
"
Violation of Bell's inequality shows that the *world* is non-local. It can be no criticism of a theory [like de Broglie-Bohm]
that it displays this feature of the world in an obvious way."
or Redhead:
"
Some sort of action at a distance - seems to be built into a reasonable attempt to understand the quantum view of reality."
and clearly I could supply several thousand more quotes from clever people along the same lines..
Just for fun, here's a typical review of Maudlin's book:
"
There are many books which discuss the issue of quantum non-locality and discuss its connections to relativity theory. The vast majority of them, however, are either un-serious popular pap, or serious tomes written by professional philosophers who are at least as confused as the authors of the pap.
Maudlin's book stands out like a beacon of light in this fog of confusion and muddle-headedness. It is accessible to anyone with a basic high-school education in math and physics, yet surpasses the vast majority of technical papers on this subject in depth, clarity, and (most importantly) correctness. If you want to understand the issue of non-locality that makes some people worry so much about quantum theory and its consistency with relativity, read this book -- study this book -- and this holds whether you are a Joe Schmoe off the street or a famous Professor from (say) Boston University."
I couldn't agree more - read it!
So, my point is that the orthodox interpretation of QM is a prescription for
avoiding fundamental questions - that is so because Bohr and Heisenberg designed it that way. It effectively debars all attempts to interpret the quantum formalism aside from their purely instrumental yield. You cannot use it to make the argument you are making.
For some reason you think this interpretation has some special status for discussing questions of this nature. It has no such status - other than purposefully restricting itself to stating the obvious. It wasn't even the first interpretation of QM - the de Broglie-Bohm one (which I strongly suspect will win out when all the old brainwashed guys die) beat it by at least two years. And in the ultra-modern era where we have to accept that quantum particles and matter waves actually exist - effectively because we can trap, see and manipulate them - Copenhagen is no longer sufficient.
So to summarize the difference:
I said (post #36):
(A) If there exists an objective reality, then Bell's/GHZ etc. theorems and subsequent experiments show that 'spooky action at a distance' is a genuine physical effect (in the absence of backwards time travel or many universes).
[I note by the way in your reponse to my post you fail to mention my three get-out clauses, thus implying my statement (A) consists of the words only between 'Bell' and 'effect'.]
ThomasT statement (I paraphrase):
(B): Because quantum physics is not about real objects, it is about the results of observations, then statement (A) is incorrect. Hence in quantum mechanics, nonlocality is acausal.
However, while the mathematical objects in quantum physics may not map onto real objects (despite the utter obviousness of de Broglie-Bohm) that does not matter. The unfortunate fact is that Bell's theorem is ultimately directly dependent neither on quantum physics, nor on the precise nature of the metaphysics. What one can say is that if there is an objective reality, that is if something which actually exists travels through the apparatus in an interference experiment, then the physical existence of nonlocality may be upheld (in the absence of backwards time travel or ..aaargghhh.. bazillions of new universes being created every time something happens). Note that this is true whatever the nature of the real thing in question. It may be a Bohmian particle and wave field, it may be just a wave function, it may be an invisible cow with bells on - it doesn't matter for the sake of this argument. It merely needs to objectively exist.
Now, I know you don't actually deny the existence of an objective reality, because you say so explicitly. I quote:
"Nobody is denying that what happens between emitters and detectors is real. But what can you say about it apart from the instrumental behavior?"
Well, given that 'whatever it is' that goes through the holes in a double-slit experiment produces a perfectly standard interference pattern then you can say a wave of some kind must go through the slits. If it wasn't a wave, then no interference pattern would be produced. (If the wave function represents 'knowledge' then how do you get interference, exactly?)
And given that the wave pattern is only built up over millions of individual particle detection events, then it's highly likely that particles go through the slits as well, and that they are 'guided' by the waves (via a 'quantum force').
Hmm.. do you recognize the theory? Wave-particle duality implying waves
and particles? No, it can't be true. Feynman said so:
"
How does it really work? What machinery is actually producing this thing? Nobody knows any machinery. Nobody can give you a deeper explanation of this phenomenon than I have given; that is, a description of it."
I don't claim that the above inferences are unique, but it certainly is very interesting that using them, one can write down a more or less obvious 'causal explanation' for just about every phenomenon of quantum physics. Ever tried explaining, say, Pauli's exclusion principle to an undergraduate using only the Orthodox interpretation (er.. "the indistinguishability of electrons leads to er.. 'statistical repulsion' through er.. the Pauli force and thus same-spin electrons - which don't er.. exist until you look at them - tend to avoid each other". Anyone?). It's just not possible with a theory that denies the possibility of explanatory clarity on a point of principle. Add the 'quantum force' - which is identical to the so-called Pauli force and whose mathematical form is sitting, usually unnoticed,
already in the QM formalism - and the explanation is easy.
Anyway, sadly, it doesn't matter what you can say about it. If the objects in an EPR experiment are real, then given our current knowledge about physics, nonlocality exists. The main difference of opinion seems to be that you think that 'realistic' means 'engaging in speculative metaphysics' rather than 'objectively existing', and that 'metaphysics' appears to be some sort of term of abuse. Realist theories of QM are no more 'metaphysical' than any other theory in physics about things that you can't see directly (curved space, quarks, black holes etc.) And at least the realistic theories themselves explain why you can't directly measure e.g. electron trajectories.
We cannot accept, as a legitimate argument form, inferences from the unobservability of a distinction to the unreality of the distinction. And I suspect you know that.