Is something wrong with statistical interpretation of QM?

[DevilsAvocado]

Physics is rooted in logic, and logic is a major branch of philosophy.

Interesting that you brought up logic, unless I'm not mistaken, Gödel's incompleteness theorem shows that any system that is sufficiently powerful, such as arithmetic, cannot be both consistent and syntactically complete.

I sure hope that universal_101 is not claiming all of mathematics wrong, because of this little 'dilemma' ...

 

[WannabeNewton]

Where am I wrong?

Do you understand the difference between superposition and proper mixtures (classical ensembles)?

 

[DevilsAvocado]

Does it mean, it is non-realist theory? In a sense that we don't know the state of the particle prior to the measurement and therefore it is the measurement which produces the state right at the moment of measuring the property of the particle. And if after measurement we find some correlations, it is because they were introduced when the entangled particles were created.

All this does not seem very non-realist(except in the Bells sense), it seems very much classical, where we don't know which pair we have until we open the box, and since the pair is entangled when let's say, the pair of socks were packed in different boxes.

Where am I wrong?

You are not wrong, the quote is dead wrong, and stuck in the OLD 1935 PICTURE of perfect correlations of ONLY deterministic left/right, up/down, on/off, 1/0, etc.

This is exactly what Bell ERADICATED from the EPR paradox; to finally solve the 20+ year long Bohr–Einstein debates, by feasible experiments including extended/more measurement settings, giving results like up/up, down/down, up/down, down/up, in different amount to get correlations like cos²(22.5°) = 85%, producing this famous curve for settings 0° to 360°:

http://upload.wikimedia.org/wikipedia/en/thumb/e/e2/Bell.svg/500px-Bell.svg.png

 

[universal_101]

... and today we can be absolutely confident that classical local realism is not a complete 'theory' – it doesn't work in experiment!

I.e. even if QM some day is superseded by a new theory – local realism is already a dead parrot.

Period.

All the above in the Bells sense of local realism! right? That is if Bells theorem is proven wrong then there is nothing wrong with classical local realism. Additionally, it is your turn to prove that non-locality or non-realism in classical sense is violated.(Ofcourse using some other alternative approach)

 

[Maui]

That is if Bells theorem is proven wrong then there is nothing wrong with classical local realism. Additionally, it is your turn to prove that non-locality or non-realism in classical sense is violated.

No. You cannot start QM from the finish line and think you've arrived there the right way. You must start at the beginning and go the whole hog. Classical realism presupposes things that are not compatible with quantum theory and experiments.

 

[stevendaryl]

All the above in the Bells sense of local realism!

What other sense is there?

 

[Nugatory]

That is if Bells theorem is proven wrong then there is nothing wrong with classical local realism

well, yes... but do you seriously think that there is any possibility that Bell's theorem (that is, his proof of the theorem that the predictions of quantum mechanics cannot be reproduced by any member of the class of theories that make a particular assumption about the joint probability distribution of two observations) is wrong?

Or are you suggesting that there might be a theory that does not make that assumption and could still be recognizably local and realistic?

 

[DevilsAvocado]

All the above in the Bells sense of local realism! right? That is if Bells theorem is proven wrong then there is nothing wrong with classical local realism. Additionally, it is your turn to prove that non-locality or non-realism in classical sense is violated.(Ofcourse using some other alternative approach)

Holy crap, yet another crackpot, if you continue along this cranky path this thread will be closed before the end of the day (local time).

Bell's theorem, in its simplest form, has a mathematical level just above primary school, but a gifted 10-yearold can without any problem grasp the meaning of it.

How old are you?

Do you understand that in our classical world 1 + 1 = 2?

Do you understand that Bell's theorem and QM proves experimentally that 1 + 1 = 3?

Do you understand that this is empirical evidence, that doesn't care about your personal preference?

Do you understand that empirical evidences never goes away, they will always be true, no matter what?

Do you understand that you are violating the rules of Physics Forums?

 

[bhobba]

Why? is it because nature itself is inherently probabilistic since no classical hidden variable can explain Quantum entanglement, or is it because there are far too many degrees of freedom involved in any particular quantum measurement.

I was hopeing you would nut it out for yoursef, but didnt.

That nature is deterministic is no more a-priori than if its probabilitic. It is simply faulty reasoning to assume determinism is more reasonable - it isn't.

What Gleason's theorem proves, is if you take the first axiom of QM as found in Ballentine, namely the possible outcomes are the eigenvalues of the associated observable, is, with a few other reasonable assumptions such as basis independence (or equivalently non contextuality) then nature is inherently probabilistic. This was not put in from the start - it naturally popped out. Such is not true classically - determinism is simply assumed.

OK, let's see, Quantum entanglement according to quantum physics says the state of the two particles are said to be entangled, if they produce opposite (or similar depending on the experiment) results every time there is similar measurement done on the two particles state. But since the two states are not co-related according to QM(i.e they are independent of each other) therefore the only solution according to QM is that the two states somehow change the state of each other depending on what is measured on the other, to get the opposite/similar final results.

Hmmmm. That's very convoluted and tortured - its not quite that difficult.

Its got to do with the vector space structure of pure states in combined systems ie the principle of superposition.

Suppose you have two particles that can be in state |a> or state |b>. If particle 1 is in state |a> and particle 2 in state |b> then the system is in state |a>|b>. Conversely if particle 1 is in state |b> and particle 2 in state |a> then the system is in state |b>|a>. But the principle of superposition applies to each of those states so the system can be in say 1/2 |a>|b> + 1/2 |b>|a>. This means neither particle is in a specific state - they are entangled with each other. Such is inexplicable classically or by classical probability theory.

Thanks
Bill

 

[bhobba]

There is a third very unspectacular possibility: Local relativistic quantum field theory is correct! That's it. No problems left.

Good point.

That's the position of this guy:
https://www.amazon.com/dp/9812381767/?tag=pfamazon01-20

Interesting read as well.

Where am I wrong?

What Vanhees is saying is that QM is actually the limiting case of a deeper theory - QFT which is the combination of QM and relativity. Many of these issues are easily handled within QFT, the detail can be found in the book above.

Thanks
Bill

 

[universal_101]

No. You cannot start QM from the finish line and think you've arrived there the right way. You must start at the beginning and go the whole hog. Classical realism presupposes things that are not compatible with quantum theory and experiments.

I agree that I should not do that, but bell's theorem is not about QM, it is about the failure of current classical local-realism to explain Quantum results. That is my point, that just because Quantum formulation produces the correct results and classical objectivity association with the state of the particle(which is purely a quantum non-real concept) does not produce the results which does not come under the domain of classical objectivism.

My point is why does Bell's theorem forces the classical objectivity to be applicable in Quantum mechanics, since the state of the particle is undefinable classically, therefore it is out of the scope of the classical physics and understandably should not produce good results. Now forcing classical objectivity on the state of the particle(which is purely a quantum non-real concept) should not infer that classical local-realism can never explain QM results. Instead one should infer that using the quantum concept of state(non-real) of a particle as a starting point, No classical theory can produce the same results.

I hope you see the difference!

 

[universal_101]

well, yes... but do you seriously think that there is any possibility that Bell's theorem (that is, his proof of the theorem that the predictions of quantum mechanics cannot be reproduced by any member of the class of theories that make a particular assumption about the joint probability distribution of two observations) is wrong?

There can't be more agreeable statement, and I don't think it is wrong when expressed like you did, very clearly. But I think, there is still hope for theories which does not make that assumption of joint probability distribution of two observations. Additionally, the above proof does not explicitly mean that non-locality or non-realism is a fact, it only means when a particular theory is used outside its domain of applicability, that particular theory does not produce good results.

Or are you suggesting that there might be a theory that does not make that assumption and could still be recognizably local and realistic?

I think there is a possibility, until we discover non-locality and/or non-realism independently.

 

[universal_101]

Holy crap, yet another crackpot, if you continue along this cranky path this thread will be closed before the end of the day (local time).

Bell's theorem, in its simplest form, has a mathematical level just above primary school, but a gifted 10-yearold can without any problem grasp the meaning of it.

How old are you?

No need to be jittery, we are just debating our views.

Do you understand that in our classical world 1 + 1 = 2?

Yes I do.

Do you understand that Bell's theorem and QM proves experimentally that 1 + 1 = 3?

That is the point, you can never prove 1+1 = 3(for a single description of nature), what you are doing is, equating the LHS(classical description of the state of the particle) to RHS(quantum statistical result), but ofcourse they should not be equal, for the two theories are not compatible.

Do you understand that this is empirical evidence, that doesn't care about your personal preference?

The Evidence that classical description of state of particle does not produce quantum statistical results, is perfectly understandable.

Do you understand that empirical evidences never goes away, they will always be true, no matter what?

Yes I do.

Do you understand that you are violating the rules of Physics Forums?

Is it because I used the phrase "Bell's theorem" and the word "wrong" in a single post.

 

[Jilang]

My point is why does Bell's theorem forces the classical objectivity to be applicable in Quantum mechanics, since the state of the particle is undefinable classically, therefore it is out of the scope of the classical physics and understandably should not produce good results. Now forcing classical objectivity on the state of the particle(which is purely a quantum non-real concept) should not infer that classical local-realism can never explain QM results. Instead one should infer that using the quantum concept of state(non-real) of a particle as a starting point, No classical theory can produce the same results.

I hope you see the difference!

Nicely put. So if there are no classical hidden variables might there still there be quantum hidden variables?

 

[Maui]

Instead one should infer that using the quantum concept of state(non-real) of a particle as a starting point, No classical theory can produce the same results[/I].

I hope you see the difference!

There is simply no other concept of 'particles' than the quantum states of the formalism. That's why they are the starting point.

You seem to tacitly assume that there may exist some other classically real stuff that may in 1028 years explain the correlations but unless you can provide evidence for that, you are threading a very narrow crackpotish path here. You are criticizing a hundred years of physics for allegedly incorrectly using the concept of quantum states and your justification for that is what? A hunch?

What is your starting point if quantum states are not to be used as a description of matter? A unicorn? Quantum theory is not a hoax and can't be overturned by bad philosophy.

 

[bhobba]

Nicely put. So if there are no classical hidden variables might there still there be quantum hidden variables?

Of course. Feynmans path integral approach is actually a hidden variable theory but of a very non trivial type that has no issues with Bell.

Thanks
Bill

 

[atyy]

Of course. Feynmans path integral approach is actually a hidden variable theory but of a very non trivial type that has no issues with Bell.

Feynman's path integral has no issues with Bell, in the sense that it isn't a local realistic theory?

 

[Vanadium 50]

we are just debating our views.

Before one can debate quantum mechanics, one needs to learn quantum mechanics.

Thread closed.