From: jos.bergervoet@xs4all.nl   
      
   On 2/4/2018 9:11 AM, Steven Carlip wrote:   
   > On 2/1/18 11:55 PM, SEKI wrote:   
   >> Consider a photon pair.   
   >>   
   >> (1) Each of paired photons is created simultaneously at the same   
   >> point, and travels at the speed of light in a direction opposite to   
   >> each other.   
   >>   
   >> (2) No or, at most, negligible interaction is possible between   
   >> photons.   
   >>   
   >> (3) No restriction is imposed on superposition of quantum waves of   
   >> photons, which are bosons.   
   >>   
   >> Then, is any correlation between paired photons earthly, other than   
   >> those determined at the point of pair creation?   
   >   
   > It depends on what you mean by correlations.   
   >   
   > In your example, I can choose to measure the polarization   
   > of each photon along any axis I choose.  Given any such   
   > axis, I will measure the photon as either having a   
   > polarization in the direction of the axis or in the   
   > perpendicular direction.  Quantum mechanics predicts the   
   > probability of each outcome, and also predicts certain   
   > correlations between the results when I measure both photons.   
      
   Now you skipped your own question: what do you mean with those   
   correlations?! Do you just base them on the matrix element   
        
   for the product of the two spin observables Sa, Sb used by   
   Alice and Bob, each with some chosen spin-axis angle?   
      
   *Or* do you insist that, somehow, two binary-valued outcomes   
   are produced? And take the classical correlation of a sequence   
   of those binary outcome pairs with the experiment repeated?!   
      
   In the latter case you run against Bell's theorem (and you   
   also must make QM non-unitary, and you probably have to solve   
   other problems..) But in the former case there is no violation.   
      
      ...   
   > Quantum mechanics predicts correlations that *violate* the   
   > Bell inequalities.  Such correlations can't be explained by   
   > what I've called local, classical correlations.  And when   
   > the experiments are done, they agree with quantum mechanics   
      
   Again the question! What does it mean that "the experiments are   
   done"? Has there only been some interaction with the observing   
   devices, described by unitary evolution in the local subspaces   
   of Alice and Bob? (The total tensor space of those 2 subspaces   
   does give separate evolution, the 2 sub-Hamiltonians commute!)   
      
   *Or* do you insist that somehow a pair of binary-valued results   
   has been created?   
      
   > -- Bell's inequalities are, in fact, violated by nature.   
      
   Only if you insist on the second meaning of "the experiments   
   are done"! (And in addition you then must explain how the   
   superposition will evolve over a non-unitary path to a single   
   outcome, which QM until now - after 100 years - has not solved,   
   and probably you will have to solve some other problems..)   
      
     ...   
   > Here are some ideas that don't work.  You can't say that when   
   > the photons are produced, they already "know" the settings   
   > of the detectors.  Experiments have been done in which the   
   > detector settings are randomly changed after the photons   
   > are already in flight.  You can't say that the experimental   
   > results are misleading because not all of the photons are   
   > actually detected.  This "detection loophole" was always a   
   > stretch, but now it's been experimentally closed.   
      
   So what *does* work is to reject the idea of wave function   
   collapse and simply accept that there are no binary-valued   
   outcome results created, but the superposition remains, and   
   simply includes the measurement device after the measurement.   
      
   Bell's inequality is then not violated.   
      
   --   
   Jos   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)