Joy Christian, "Disproof of Bell's Theorem"

Nugatory

The paper is arguing for multiple-worlds as a local and realistic interpretation that is not counterfactually definite (no history includes the measurement not made) but also is not even factually definite (you get different facts in diferent histories). It's internally consistent and actually kinda easy to swallow... Although that may be because if you've managed to gulp down the multiple-worlds camel, after that everything is easy to swallow.

The first section has a really good explanation of the small-angle version of Bell's argument.

mbd

For the sake of getting past semantics, then, by realism I mean "scientific realism" per the article I linked to above (here too) which illuminates the distinction.

http://arxiv.org/abs/0902.3827

It must be noted, though, that the definition of "reality" in EPR (1935) is not in fact a definition but, rather, a criterion with scope limited only to the purposes of the argument. And, there is no definition of reality at all in Bell (1964). Bell's own recognition of the implicit assumptions in his work played out over subsequent years.

Einstein's definition is: "If, without in any way disturbing a system, we can predict with certainty (i.e., with probability equal to unity) the value of a physical quantity, then there exists an element of physical reality corresponding to this physical quantity." He then goes on to say that this a sufficient, but not necessary, condition of reality.

DrChinese

He also says that these must be considered as simultaneously real... that any other view is unreasonable. Back then, the semantics was not debated quite like today. Bell didn't even bother to mention the definition, thinking (I believe) that EPR's take was adequate for scientists.

audioloop

the definition of realism/reality goes beyond physics.

Nugatory

Quite true, but because physics tries to describe the R-word world, it's not always practical to completely avoid using the R-word.

Often (perhaps in all pre-QM physics and outside of discussions of QM interpretations) this isn't a problem. Samuel Johnson ("I refute it thus") and Potter Stewart ("I know it when I see it") are good enough, and detailed hair-splitting discussions of what the R-word means are irrelevant distractions.

But when we do discuss QM interpretations... It's good practice to try to be explicit about what meaning we have assigned to the R-words, CFD, and the like.

Darwin123

I thought this was a Physics Forum!
I am so sorry. I am in the wrong place!

mbd

The conceptual and practical challenges in defining "realistic" are a consequence of the fact that we're trying to talk about the system and the interfaces to that system as if these are separate things.

By separating the system in this way, we see experiments to be the act of making inputs to that system, collecting outputs from that that system, and then evaluating the information with mathematical models. We're asking: does our mathematical model of what's inside produce the same outputs as Nature when given the same inputs?

But, the veracity of what we infer from this process depends critically on the veracity of our understanding of what are the inputs and outputs.

The decades long process of recognizing, defining, and experimentally ruling out, the various loopholes in EPR experiments shows the significant challenges of this process.

In CHSH, we assume that we are inputing two particles into two measuring apparatuses. Well, more precisely, we assume that if two particles are detected sufficiently coincidentally, then we have input two particles into the measuring apparatuses. We don't know this, however.

This is an assumption that, it would seem, we cannot experimentally prove due to Heisenberg. Why? If we are to detect the presence of the particles prior to their entry into the measuring apparatuses, we break their presumed entanglement and thus lose the correlations of measurements.

So, we are precluded from experimentally confirming the veracity of our understanding of the inputs and the outputs to this experiment. Just like we cannot measure, with arbitrary precision, both the momentum and location of a particle, we cannot know with conclusive precision the inputs and outputs to this experiment.

This is, at least conceptually, the essence of the challenge of performing a "loophole free" CHSH experiment.

DrChinese

As I have repeated, you are free to define "realistic" differently than others. I would not agree with your characterization of this discussion per your above. There is a good definition and it is not much debated (except by local realists looking for an out).

Further, the concept of a so-called loophole free Bell test is quite outside the scope of this thread. It really belongs in a separate one, and this is a fairly technical subject. Again, your characterization of the debate here is not accurate. All of the loopholes have been closed, for example. The current debate is more around having a single experiment where all are closed simultaneously. Here are a couple of recent papers by some of the top teams in this area:

http://arxiv.org/abs/1111.0760

http://arxiv.org/abs/1206.2289

Again, we should move this to a different thread to continue. This has nothing to do with Bell's Theorem or Christian's work.

mbd

Actually, DrChinese, the papers you mention very much confirm my viewpoint.

Firstly, both, at the outset, confirm that a loophole-free test has not been performed.

Second, the Sciarrino paper aims to address the issue of determining whether coincident detections really are associated with coincident emissions. This is exactly the issue I raised about inputs/outputs in my posting!

Third, the Zeilinger paper refers to the goal of closing of all MAJOR loopholes in one experiment, not the closure of ALL loopholes in one experiment. And, the experiment presented just rules out one class of local realist theories in a loophole free test, not all classes of theories.

In other words, there is nothing incorrect or outside the mainstream in my post. I am simply making an effort to explain why this question has been open since 1935, even though a few fervent non-localists seem to think it's closed.

So, DrChinese, can you please state in a form without ambiguity the definition of realism to which you've been referring? A quote from a paper would be fine too. The first two papers you referred the forum to as definitive on "realism" don't actually define realism at all, so a reference to a paper that does would be most helpful.

mbd

DrChinese, here is a paper to which I was directed by a member of the editorial board of a major physics journal because it is an example of how "non-locality" is far from being a prevailing viewpoint. And, it defines realism as I do (on page 3).

http://arxiv.org/abs/1108.0001

DrChinese

EPR, 1935, as I keep telling you.

"If, without in any way disturbing a system, we can predict with certainty (i.e., with probability equal to unity) the value of a physical quantity, then there exists an element of physical reality corresponding to this physical quantity. It seems to us that this criterion, while far from exhausting all possible ways of recognizing a physical reality, at least provides us with one such way, whenever the conditions set down in it occur."

Then...

"Indeed, one would not arrive at our conclusion if one insisted that two or more physical quantities can be regarded as simultaneous elements of reality only when they can be simultaneously measured or predicted. On this point of view, since either one or the other, but not both simultaneously, of the quantities P and Q can be predicted, they are not simultaneously real. This makes the reality of P and Q depend upon the process of measurement carried out on the first system in any way. No reasonable definition of reality could be expected to permit this."

This is generally accepted as "realism". As I say, you are free to define as you like. It just won't match up to the definition used by most. Bell didn't even bother to mention it as a definition assuming that EPR covered it and that his audience would read and understand that 1935 paper.

And you keep mentioning your viewpoint and mentioning papers which "confirm" that viewpoint. We are not here to listen to individual viewpoints. I have mine too! The idea is to learn something about physics. In that regard, a moderated forum insures we stay on track and share things which those following the thread will find useful. You keep pulling the thread away from Christian's work and towards ideas you have (such as your post #213 preceding). If you want to discuss the definition of realism as it relates to QM, I again recommend you start a thread on it. I will gladly discuss it with you there. I am familiar with the author's work you cite and would be happy to comment.

mbd

DrChinese, Einstein correctly describes his condition as "sufficient, but not necessary", and you seem to have missed that point and are using it to mean "necessary and sufficient".

These subtleties go to the heart of the issue and why this is an open question in physics.

Further, please stop mischaracterizing my posts. You do not have nearly as deep an understanding of this material as you seem to think and, as a result, you are pushing a viewpoint that is seriously misleading with respect to the state of the science.

DrChinese

I am hurt.

DrChinese

Spoken like a person with a penchant for semantics.

mbd

Einstein qualifies his criterion (note, it is not a definition) by saying "Regarded not as a necessary, but merely as a sufficient, condition of reality, this criterion is in agreement with classical as well as quantum-mechanical ideas of reality."

The distinction is essential, not semantic.

According to Einstein's criterion, if a system meets it, then it is realistic. If a system does not meet the condition, Einstein's criterion is silent as to whether the system is realistic or not.

Here's one system that will help clarify the point:

Consider a pot of water, and let the maxim "a watched pot never boils" be true.* We can, at any time, "measure" the system to see if the system is boiling or not boiling. Now, try to measure the system to determine when it starts boiling. You cannot, at least not with arbitrary precision.

But, clearly, there is physical reality to the event that is the instant it starts boiling. Right? We can in fact predict quite precisely when the event occurs, but we cannot observe it. In fact, we can predict it without disturbing the system just as Einstein's criterion requires but we cannot directly observe the event.

As for simultaneous reality, assume identical pots A, B. We can, at any instant, measure A and know if B is boiling or not at that very instant. Note, though, we can only do this once and, unless A is boiling, the answer is valid only at that instant.

Now, let the two pots be slightly different and ask, which boils first? There is physical reality to this, there is an answer, and we can predict the answer. But, we cannot, through only the measurement "is the pot boiling or not?" answer this question.

This illuminates both why a precise definition of reality is essential and why it is essential to know what you are actually measuring or observing.

*We can, in fact, construct a pot that, when watched, does not boil if watching requires lifting of the lid and when not covered the heat loss matches or exceeds the heat input from the burner.

DrChinese

Glad to know it is a criterion and not a definition. LOL.

EPR is a local realist's defense. EPR define "local realism"* by marrying 2 assumptions to the "elements of reality" criterion. We can show sufficiently (LOL) that elements of reality exist for photon polarization (as our example) at angles 0, 120, 240 (same as -120). This is experimentally verifiable and has never been much in question**. They ASSUME that the following are true (see last few paragraphs of EPR):

1. There are no FTL influences (i.e. no spooky action at a distance).
2. The individual physical quantities are considered to be simultaneous elements of reality. Otherwise, they state for the local realist position, reality here is dependent on the nature of a measurement there, and that would be unreasonable.

Bell showed that there are no datasets for angle settings 0/120/240*** which also match the QM (and classical optics) predictions: cos^2(theta) in the case of photons. IF you consider the EPR criterion of element of reality to have been SUFFICIENTly satisfied for 0/120/240 (not much to quibble about that); AND you accept that experiments support the cos^2 relationship QM predicts****, THEN either 1. or 2. (or both) are unwarranted assumptions. QED.

So: There is one criterion, and 2 assumptions put forth by EPR. Aspect et al plus hundreds more have demonstrated that the QM predictions are accurate. What DON'T you agree with that EPR says?

* The phrase is never used as such.
** Of course post-Bell local realists question everything, including the definition of "is".
*** Bell does not use these angles specifically, they are just one set of many possible. Makes no difference how many as long as there is one.
**** Notice that there is no need to simultaneouly measure 3 of anything to see this relationship. This is lost on Christian and many other writers. This has been experimentally verified to well over 30 standard deviations.

Mathematech

post-Bell realists most definitely question the signficance of postulate 2 and what it really has to do with philosophical realism, because it amounts to saying that reality is screwy if your lap or fist disappears.