Where is the flaw with predetermined entanglement state?

[DrChinese]

I feel that Complete / Absolute / Total / Omni-determinism is a better word for it. SUPER sounds so.. weird. All it really is, is complete determinism. Which shouldn't be too hard to swallow if you already accept either Bohm or Many Worlds which is equally absolute in their determinism

Superdeterminism - under any name - is ridiculous. Just try to formulate in a scientific (and falsifiable) manner and you will see just how so!

For example: if all interactions are superdetermined and local and realistic (the reason superdeterminism was invented), then every particle in the universe must carry a complete copy of its "answer" to every measurement (question) possible - with every other particle in the universe to which it ever has or will interact. That is because entanglement can be swapped from particle X to particle Y and you never know which particle might be entangled with what other particle. Basically you are talking about an infinite amount of information being stored locally in every particle in the universe. Of course that information is "hidden" because there is no other evidence of it.

 

[zonde]

Then please scrutinize all those experiments and offer a formal rebuttal to them. Otherwise, all you have done is present an objection to them based on a matter of personal taste.

Where did you get I have objections against these experiments? I have objections against your interpretation of these experiments. Besides my objections are not strict - I presented a way how one can still hold to this viewpoint. In particular one can become a philosopher who does not trust his senses an leave science to those who believe in realism.
As I understand you earn for your living by doing experimental physics, right? So becoming a philosopher who does not trust his senses would be quite extraordinary turn for you, I believe. So I don't quite understand your position. You can't have your cake and eat it too.

 

[stevendaryl]

I would say that idea of experimental results contradicting classical realism is so extraordinary that it's hard to take it seriously. Science takes realism for granted and if you consider possibility that realism is not acceptable then you just have to throw out all the science (and even more) and start from scratch (with philosophy). Additional problem is that such philosophical directions already have been explored and are not very popular.

I sort of agree with you, that a lot (most? all?) of science is done with an implicit idea of a universe external to us that we are learning about through experiment and observation. However, a more limited view of science is that it is about making predictions, of the form: If I perform such and such an experiment, I will get such and such result. That limited view of science doesn't require realism.

 

[stevendaryl]

Where did you get I have objections against these experiments? I have objections against your interpretation of these experiments. Besides my objections are not strict - I presented a way how one can still hold to this viewpoint. In particular one can become a philosopher who does not trust his senses an leave science to those who believe in realism.
As I understand you earn for your living by doing experimental physics, right? So becoming a philosopher who does not trust his senses would be quite extraordinary turn for you, I believe. So I don't quite understand your position. You can't have your cake and eat it too.

The sort of anti-realism suggested by violations of Bell's inequalities doesn't amount to rejecting experimental results. Instead, it amounts to rejecting the idea that there is a definite "state of the world" outside of experimental results.

 

[ZapperZ]

Where did you get I have objections against these experiments? I have objections against your interpretation of these experiments. Besides my objections are not strict - I presented a way how one can still hold to this viewpoint. In particular one can become a philosopher who does not trust his senses an leave science to those who believe in realism.
As I understand you earn for your living by doing experimental physics, right? So becoming a philosopher who does not trust his senses would be quite extraordinary turn for you, I believe. So I don't quite understand your position. You can't have your cake and eat it too.

Please note that that was not MY interpretation. If you read those papers that I referenced to, there is a clear reference to realism and what they are testing. The Leggett inequality was formulated with that in mind! That is why I said that if you disagree with that, you should be the one doing the rebuttals to those papers!

I don't get this reference to philosophy. If anything, you were the one who was arguing this based on philosophy. YOur post in #67 contains no physics, only personal preference. The fact that "realism", as defined within this context, can actually be tested experimentally means that it has been brought out of philosophy and into physics, the very same way the EPR paradox was brought out of philosophical argument and into physics when John Bell formalize its test. So if you have issues with this, let's see you rebut, say, Leggett's formalism.

Zz.

 

[stevendaryl]

Superdeterminism - under any name - is ridiculous. Just try to formulate in a scientific (and falsifiable) manner and you will see just how so!

For example: if all interactions are superdetermined and local and realistic (the reason superdeterminism was invented), then every particle in the universe must carry a complete copy of its "answer" to every measurement (question) possible - with every other particle in the universe to which it ever has or will interact. That is because entanglement can be swapped from particle X to particle Y and you never know which particle might be entangled with what other particle. Basically you are talking about an infinite amount of information being stored locally in every particle in the universe. Of course that information is "hidden" because there is no other evidence of it.

I agree with you that superdeterminism is unpalatable as a physical theory, but it wouldn't necessarily require infinite information stored in every particle. Instead, superdeterminism could be achieved through ordinary determinism plus very fine-tuned initial conditions.

 

[Quantumental]

I agree with you that superdeterminism is unpalatable as a physical theory, but it wouldn't necessarily require infinite information stored in every particle. Instead, superdeterminism could be achieved through ordinary determinism plus very fine-tuned initial conditions.

But why is it then unpalatable? We live in a infinite ocean of somethingness. Is it really that hard to accept that everything is fine tuned at the beginning?

 

[stevendaryl]

But why is it then unpalatable? We live in a infinite ocean of somethingness. Is it really that hard to accept that everything is fine tuned at the beginning?

Yes. Fine-tuning is like explaining something by "it's just a coincidence".

 

[Quantumental]

Yes. Fine-tuning is like explaining something by "it's just a coincidence".

Not really. Check out Gerard 't Hoofts proposals

 

[stevendaryl]

Not really. Check out Gerard 't Hoofts proposals

If we're talking about the same thing, I feel the same way about his proposals. Are you talking about his classical model for quantum mechanics?

 

[Derek Potter]

I sort of agree with you, that a lot (most? all?) of science is done with an implicit idea of a universe external to us that we are learning about through experiment and observation. However, a more limited view of science is that it is about making predictions, of the form: If I perform such and such an experiment, I will get such and such result. That limited view of science doesn't require realism.

Actually even such a prediction assumes the onticity of the formula - otherwise it can't refer to real observations.
EPR does not require the rejection of realism, it requires the rejection of direct realism. In other words our view of the universe needs to be modified drastically but, very importantly, we can still think of it as real.
From what I've hear of it, the Leggett inequality violations confirm that the issue is a particular view of reality, that a system has a unique and definite state. That little dent in common-sense seems here to stay.

 

[StevieTNZ]

From what I've hear of it, the Leggett inequality violations confirm that the issue is a particular view of reality, that a system has a unique and definite state. That little dent in common-sense seems here to stay.

The Leggett inequality only rules out certain classes of non-local hidden variables. Therefore realism is still possible, as it does not rule out Bohmian Mechanics.

The inequality I want tested is the Leggett-Garg inequality, which tests macro-realism. But if Bohmian Mechanics and QM give the same predictions, then realism could still be viable even if the inequality is violated.

 

[Derek Potter]

The Leggett inequality only rules out certain classes of non-local hidden variables. Therefore realism is still possible, as it does not rule out Bohmian Mechanics.
The inequality I want tested is the Leggett-Garg inequality, which tests macro-realism. But if Bohmian Mechanics and QM give the same predictions, then realism could still be viable even if the inequality is violated.

I do not follow the logic of that. If (and it's a big if) LG violation only rules out some classes and doesn't rule out BM then that does not mean realism is back on the table.

I'm not at all sure BM is realist in the required sense anyway. Sure there is a real wave and a real particle, but what of superpositions? The particle is like a predetermined collapse riding along with the wave, but how does BM cope the fact that Alice and Bob have not yet decided what basis to use? That's a genuine question, by the way. I suspect I know the answer - it doesn't - but I don't actually know.

 

[atyy]

I do not follow the logic of that. If (and it's a big if) LG violation only rules out some classes and doesn't rule out BM then that does not mean realism is back on the table.

I'm not at all sure BM is realist in the required sense anyway. Sure there is a real wave and a real particle, but what of superpositions? The particle is like a predetermined collapse riding along with the wave, but how does BM cope the fact that Alice and Bob have not yet decided what basis to use? That's a genuine question, by the way. I suspect I know the answer - it doesn't - but I don't actually know.

BM is realist in the sense that it solves the measurement problem in the most boring way possible.

BM deals with the preferred basis problem by assuming that position is the only thing one measures.

 

[atyy]

But why is it then unpalatable? We live in a infinite ocean of somethingness. Is it really that hard to accept that everything is fine tuned at the beginning?

No. It is not unpalatable (people say these things, but it's not scientific). Rather, it is impractical, because we cannot write down such a theory. So basically, we have already done all the research we can on superdeterminism. The open questions are, if we cannot write down the true theory of everything (say superdeterminism or whatever), are there intermediate steps in theory we can take that will make sense to us in the traditional scientific framework? Maybe the answer is no. However, Bohmian Mechanics shows that it is too early to give up, and there's probably room to explore the other openings allowed by Bell, such as retrocausation and many-worlds.

 

[Derek Potter]

BM is realist in the sense that it solves the measurement problem in the most boring way possible.
BM deals with the preferred basis problem by assuming that position is the only thing one measures.

Really? What does entanglement look like in a position basis?

 

[atyy]

Really? What does entanglement look like in a position basis?

It's the same as in QM.

The idea is that we can measure momentum by measuring position - we just cannot do it measure the canonically conjugate position at the same time. But we can use a different position to indicate momentum. For example, in the double slit experiment, the momentum of the particle just after the slit can be read by its position at a distant screen.

Also, QM doesn't say that a particle cannot have a trajectory. It says that a particle cannot have position and momentum simultaneously. So we can just choose to have particles with position but no momentum.

 

[stevendaryl]

Really? What does entanglement look like in a position basis?

In this paper, the EPR experiment for spin-1/2 particles is analyzed from the point of view of Bohmian mechanics.

http://www.tau.ac.il/~vaidman/lvhp/m115.pdf

 

[Derek Potter]

It's the same as in QM.

The idea is that we can measure momentum by measuring position - we just cannot do it measure the canonically conjugate position at the same time. But we can use a different position to indicate momentum. For example, in the double slit experiment, the momentum of the particle just after the slit can be read by its position at a distant screen.

Also, QM doesn't say that a particle cannot have a trajectory. It says that a particle cannot have position and momentum simultaneously. So we can just choose to have particles with position but no momentum.

OK. However that just covers the particle position. I was more interested in the wave, which never collapses and therefore, I assume, propagates nonlocaly - in a space of 6 or more dimensions. It would seem - please correct me if I'm wrong - that the wavefunction/pilot wave for the two particles together cannot be a function of the two separate waves. So we are back to the wave of A not existing on its own but only being defined in relation to the wave of B. Which is the very definition of non-realism. Is that correct?

 

[atyy]

OK. However that just covers the particle position. I was more interested in the wave, which never collapses and therefore, I assume, propagates nonlocaly - in a space of 6 or more dimensions. It would seem - please correct me if I'm wrong - that the wavefunction/pilot wave for the two particles together cannot be a function of the two separate waves. So we are back to the wave of A not existing on its own but only being defined in relation to the wave of B. Which is the very definition of non-realism. Is that correct?

If you are talking about Leggett's definition of realism, which is a technical one, I don't know.

 

[zonde]

Please note that that was not MY interpretation. If you read those papers that I referenced to, there is a clear reference to realism and what they are testing.

I read very carefully your reference about Wheeler's delayed-choice experiment with helium atoms. I could not find anything similar to your statement.
The best bet would be this:
"Wheeler's thought experiment is important since it tries to force a classical view of reality on to a quantum system."
It is quite a stretch by itself and yet it does not go as far as your statement.

The fact that "realism", as defined within this context, can actually be tested experimentally means that it has been brought out of philosophy and into physics

You can of course use the same word in physics as used in philosophy but it's confusing and I would say it's attempt to do philosophy disguised as physics.

Say we use some "word" in one sense. I redefine the "word" in different sense and falsify it in this second sense. Then I claim that "word" is falsified while the "word" is generally understood in first well established sense and is obviously not falsified in that first sense. Do you see the fallacy?

 

[ZapperZ]

Fact check: what do you think is the definition of "realism" as used here in theses PHYSICS papers and the one being addressed in Leggett inequality?

Zz.

 

[zonde]

However, a more limited view of science is that it is about making predictions, of the form: If I perform such and such an experiment, I will get such and such result. That limited view of science doesn't require realism.

In some idealized sense your argument is valid but ... scientific model contributes to knowledge of society when you can share it (communicate it), share results of experimental tests, repeat experiments and such things. It all relies on realism.
Besides new model would most certainly rely a lot on existing knowledge in order to make predictions (experimental equipment, design of experiment). Can you review all existing knowledge in light of some non-realistic model? Say we have arrived at existing knowledge by throwing out non-realistic models. You can't really review all discarded models.

 

[Derek Potter]

If you are talking about Leggett's definition of realism, which is a technical one, I don't know.

Nothing so specific. I'm just groping towards understanding what a real but non-local model could mean. I don't seem to be getting very far. No matter, I'll brush up on BM after I've fixed the measurement problem in MWI At least I have an idea of what I'm up against now, thanks.

 

[zonde]

Fact check: what do you think is the definition of "realism" as used here in theses PHYSICS papers and the one being addressed in Leggett inequality?

There is no definition of realism in paper about Wheeler's delayed choice experiment as word "realism" is not used there at all.
I don't know about Leggett inequalities but I suppose it's some sort of realism that requires that particle observables are determined by non-contextual variables (and that allows non-locality).

 

[ZapperZ]

Then maybe, BEFORE you attack, that you understand the definition that has been used when we talk about "realism" in physics AND in the context that of this topic. I had been explicit in invoking the Leggett formalism here, which I thought was sufficient to clarify the exact definition of what I was referring to. To hear now that you didn't even bother to figure that out and yet were quick to criticize on it is ridiculous.

In case you are too lazy to look, these things have been posted elsewhere already:

https://www.physicsforums.com/threads/recent-noteworthy-physics-papers.127314/page-4#post-1599072
https://www.physicsforums.com/threads/recent-noteworthy-physics-papers.127314/page-2#post-1307660

Zz.

 

[zonde]

Then maybe, BEFORE you attack, that you understand the definition that has been used when we talk about "realism" in physics AND in the context that of this topic. I had been explicit in invoking the Leggett formalism here, which I thought was sufficient to clarify the exact definition of what I was referring to. To hear now that you didn't even bother to figure that out and yet were quick to criticize on it is ridiculous.

Let me repeat this particular question:

Say we use some "word" in one sense. I redefine the "word" in different sense and falsify it in this second sense. Then I claim that "word" is falsified while the "word" is generally understood in first well established sense and is obviously not falsified in that first sense. Do you see the fallacy?

 

[atyy]

Nothing so specific. I'm just groping towards understanding what a real but non-local model could mean. I don't seem to be getting very far. No matter, I'll brush up on BM after I've fixed the measurement problem in MWI At least I have an idea of what I'm up against now, thanks.

BM is realistic in the common sense classical physics way. There is a subtlety as to whether the "wave function" in BM is real or not, since there is more than one wave function, but to start we can ignore that. BM is nonlocal in the sense that the wave function in QM is nonlocal, since it is in Hilbert space. The position of a particle depends on the wave function, so it is nonlocal. Basically, QM itself is nonlocal, if the wave function is taken to be real. BM takes over this nonlocality and solves the measurement problem by introducing hidden variables, so that there is naive reality and an observer is not required to determine what is real.

 

[Drakkith]

Thread locked, pending moderation.