DAVID: I take you back to Feynman. Paraphrased: If someone tells you they understand quantum theory, they lie. The amazing part is that the formulas work.
> 
> dhw: I do wish they would at least lie coherently.-Now there is a claim to do away with Feynman and use a newly invented math tool, which of course is not reality:-https://www.simonsfoundation.org/quanta/20130917-a-jewel-at-the-heart-of-quantum-physics/-"the amplituhedron, a newly discovered mathematical object resembling a multifaceted jewel in higher dimensions. Encoded in its volume are the most basic features of reality that can be calculated — the probabilities of outcomes of particle interactions."-"Locality is the notion that particles can interact only from adjoining positions in space and time. And unitarity holds that the probabilities of all possible outcomes of a quantum mechanical interaction must add up to one. The concepts are the central pillars of quantum field theory in its original form, but in certain situations involving gravity, both break down, suggesting neither is a fundamental aspect of nature.
 
In keeping with this idea, the new geometric approach to particle interactions removes locality and unitarity from its starting assumptions. The amplituhedron is not built out of space-time and probabilities; these properties merely arise as consequences of the jewel's geometry. The usual picture of space and time, and particles moving around in them, is a construct."-What these folks are doing is constructing their own mental math reality. Ruth's postulate, echoing Heisenberg, is that the quantum uncertainty layer of reality, does not exist in this system. It may help in computations, but there is no evidence it is real as a construct of reality.


> Dhw: I'm beginning to suspect that the scientists themselves quite literally don't "know" what they're talking about.
> 
> DAVID: I take you back to Feynman. Paraphrased: If someone tells you they understand quantum theory, they lie. The amazing part is that the formulas work.
> 
> dhw: I do wish they would at least lie coherently.-I think we have exhausted the subject.


> dhw: So if Alice sends him a dollar, he can't receive more than a dollar. Hardly worth making a song and dance about. And I still don't know what "information causality" means, or why you find it so important that you put it in bold.-Because I think the universe runs on information supplied by the Creator.-
> 
> Dhw: On the contrary, these folks REJECT the idea that all of this represents "something real out in the world", and insist that the constructs are subjective! Ruth regards quantum states as "ontologically real possibilities existing in a pre-spacetime realm [...] These possibilities are taken as real because they are physically efficacious, leading indeterministically to transactions which give rise to the empirical events of the spacetime theatre." And the problem of subjectivism "evaporates" because the transaction "is simply observed differently by the different observers" (which in my book = subjectivism). Yes, I am mightily confused.-Again, these folks don't know or care about Ruth's concepts. I don't think they reject as ignore other approaches.-
> dhw: I like the image of the semi-permeable membrane, which is far more comprehensible than what seem to me to be contradictory and often nebulous arguments that even you obviously find difficult to clarify. Your syntax above is misleading. Perhaps it WOULD all make sense if we could reside on the other side, but we can't, so it doesn't...... I'm beginning to suspect that the scientists themselves quite literally don't "know" what they're talking about.-I take you back to Feynman. Paraphrased: If someone tells you they understand quantum theory, they lie. The amazing part is that the formulas work.


> Thank you. Sadly I remain just as confused. Now the authors seem to be saying that if Alice sends Bob m bits of information about her quantum experiment, Bob can't gain more than m bits of information about the non-quantum world. Is it not possible for Bob to see connections that Alice doesn't see? After all, the authors think that every construct is subjective (see below). And I still don't know what is meant by "information causality". Perhaps you can define it and explain why it is so important.-I interpret this to mean that Bob cannot receive any more information than Alice sends.-> DAVID: Copenhagen was just a way to go forward and not worry about the confusion.[/i]
> 
> On the contrary, these folks REJECT the idea that all of this represents "something real out in the world", and insist that the constructs are subjective! Ruth regards quantum states as "ontologically real possibilities existing in a pre-spacetime realm [...] These possibilities are taken as real because they are physically efficacious, leading indeterministically to transactions which give rise to the empirical events of the spacetime theatre." And the problem of subjectivism "evaporates" because the transaction "is simply observed differently by the different observers" (which in my book = subjectivism). Yes, I am mightily confused.-I think most people still want quantum characteristics to act as if they are totally part of our reality. They are not. I still think of the dividing wall as a semi-permiable membrane. Some comes through, some doesn't, but it all makes sense if we could reside on the other side.


> "Pawłowski and his colleagues have found that this postulate is respected by classical physics and by standard quantum mechanics, but not by alternative theories that allow for stronger forms of entanglement-like correlations between information-carrying particles. For that reason, the group writes in their paper, "information causality might be one of the foundational properties of nature" — in other words, an axiom of some future, reconstructed quantum theory." (my bold)
> 
> dhw: Apparently information causality says "that if one experimenter (call her Alice) sends m bits of information about her data to another observer (Bob), then Bob can gain no more than m classical bits of information about that data — no matter how much he may know about Alice's experiment."
> 
> dhw: As you have put the sentence in bold, it's clearly important to you, but I'm totally flummoxed. I'd be grateful if first you would explain what is meant by "classical" information.-Classical information is the information at the non-quantum level. It is Newton's classical science.- If the authors are saying that Bob will not gain more information from what Alice has sent him than the information she has sent him, it's like saying that if I give you a dollar, I'm not giving you more than a dollar. Not exactly startling. On the other hand, if Bob is given additional information by one of Alice's colleagues, might he not "gain" more than she has sent him? The authors give no further explanation of "information causality", so I hope you can sympathize with my confusion and can tell us what you understand by the term.
> 
> http://www.nature.com/news/physics-quantum-quest-1.13711?WT.ec_id=NATURE-20130912&#... 
> QUOTE: "Still, this does seem an odd way for the Universe to behave. And this is what prompted Fuchs to call for a fresh approach to quantum foundations. He rejected the idea, held by many in the field, that wave functions, entanglement and all the rest represent something real out in the world (see Nature 485, 157...158; 2012). Instead, extending a line of argument that dates back to the Copenhagen interpretation, he insisted that these mathematical constructs are just a way to quantify "observers' personal information, expectations, degres of belief"."
> 
> dhw: In other words, as we discussed on our epistemological thread, whatever conclusions are drawn will be subjective. I had great difficulty following Ruth's arguments against subjectivism in her Chapter 7, and if experts in the field can't agree, how can a layman possibly know what is true and what is not?-Your confusion is because these folks are ignoring Ruth. She recognizes more than they do Heisenberg's wall of uncertainty and the confusion it brings. These folks keep trying to interpret quantum phenomena as if they are fully within our reality and they are not. They are probabilities and one can only average what to expect. Copenhagen was just a way to go forward and not worry about the confusion.