B Is this a "fair" description of entanglement for a student?

[atyy]

(i.e., it won't obey the probabilities given by the wave function).

This statement is wrong. The probabilities will be those given by the wave function. After the measurement of one spin, the wave function is altered so that it correctly predicts the probabilities observed when the second spin is subsequently measured.

 

[bhobba]

I'm skeptical that Einstein believed wrong interpretation of the theorem. When Bohm claimed in his textbook that hidden variables were impossible, Einstein was one of those who pointed out the flaw in Bohm's reasoning.

I don't know if his reasoning was Von-Neumann's. Yes - its possible he knew it was bollocks - but I haven't read he knew the flaw. Greta was ignored - but could they ignore Einstein?

Thanks
Bill

 

[bhobba]

Einstein did not ignore Bohm's papers. He just thought the solution was not beautiful (and that a more beautiful hidden variables theory could be obtained). In fact, Einstein was central to the development of Bohmian mechanics. Bohm had made the erroneous claim that quantum mechanics is inconsistent with hidden variables in his textbook. Einstein pointed out to Bohm that the claim was based on wrong reasoning, leading Bohm to eventually develop Bohmian mechanics.

Yes - along with many things about Einstein explained in Subtle is the Lord. That's why I didn't think Einstein knew the flaw because its not mentioned there.

Thanks
Bill

 

[atyy]

I don't know if his reasoning was Von-Neumann's. Yes - its possible he knew it was bollocks - but I haven't read he knew the flaw. Greta was ignored - but could they ignore Einstein?

I'm not sure what the exact history is about Von Neumann's wrong interpretation, Grete Hermann and Einstein, but here it says that Einstein pointed out the flaw in Bohm's claim in his textbook that hidden variables are impossible: http://www.bohmianmechanics.org/background/history-of-bohmian-mechanics.html.

Also, the standard 1961 textbook of Messiah does say that hidden variables cannot be ruled out and associates the hidden variable programme with Einstein. Messiah goes on to use Copenhagen (for the practical purpose of doing quantum mechanics) without ruling out hidden variables.

 

[DrChinese]

Also, the standard 1961 textbook of Messiah does say that hidden variables cannot be ruled out and associates the hidden variable programme with Einstein. Messiah goes on to use Copenhagen (for the practical purpose of doing quantum mechanics) without ruling out hidden variables.

Local hidden variables were not so clearly ruled out in 1961, so the Einstein program could have been considered viable at that time.

 

[bhobba]

Also, the standard 1961 textbook of Messiah does say that hidden variables cannot be ruled out and associates the hidden variable programme with Einstein. Messiah goes on to use Copenhagen (for the practical purpose of doing quantum mechanics) without ruling out hidden variables.

I think after Gleason published his theorem (1956 I think) the assumption was so obvious it could not be ignored. To be specific the assumption made was if A and B are two operators the addition of the expected outcomes is related simply ie if E(O) is the expected outcome of observable O then from a simplistic understanding of expectations you naturally think E(A) + E(B) = E(A+B). This is the assumption Von-Neumann made and is so reasonably obvious when you read the book you don't even bother questioning it. Greta did and saw it didn't necessarily hold up. But such was Von_Neumann's reputation people didn't listen to her - but may have listened to Einstein - he is one of the few that can stand up to Von-Neumann reputation wise. In proving Gleason's theorem you prove that is true - but the assumption is the probability is not basis dependent - called non-contextuality. Once you have seen that Von-Neumann is then quite suspect.

Thanks
Bill