From: bergervo@iae.nl   
      
   On 3/3/2018 9:47 AM, richalivingston@gmail.com wrote:   
   > On Wednesday, February 28, 2018 at 2:35:22 PM UTC-6, SEKI wrote:   
   >> On Tuesday, February 27, 2018 at 1:58:46 PM UTC+9, Tom Roberts wrote:   
   >>> On 2/26/18 9:05 AM, richalivingston@gmail.com wrote:   
   >>>> [treating the null interval between emission and detection literally]   
   >>>   
   >>> But one can have entanglement for massive particles, for which the   
   >>> interval between emission and detection is not zero.   
   >>>   
   >>> Note also that entanglement does not involve "the nonsense of one   
   >>> detector determining, instantaneously, the result at a detector outside   
   >>> its lightcone", it only yields a CORRELATION between detectors' results.   
   >>   
   >> Let's assume that the source is located at the origin of Cartesian   
   >> coordinate system.   
   >> In some experimental settings, each of emitted paired particles is   
   >> detected at the same time. In this case, a detection of a particle   
   >> can never affect the other detection.   
   >> So, in the Bell's context, entanglement is considered to be an illusion,   
   >> whether emitted paired particles are massless or not.   
   >>   
   >> Am I wrong?   
   >   
   > Just declaring that the entanglement is an illusion does not help   
   > understand the underlying physics.   
      
   OP (SEKI) is not 'just' saying that it is an illusion, but is saying   
   that  entanglement is an illusion because 'detection' cannot affect   
   some other detection in a distant place.   
      
   This is logically wrong. The conclusion should be that detection is an   
   illusion! At least the notion of detection where there is a collapse   
   of the state into one of the components of the superposition. If that   
   does not happen then the entanglement can still be present, it is   
   nothing but a correlation between complex amplitudes that is caused   
   by common origin and propagates nicely with sub-luminal speed.   
      
   For the rest I completely agree with OP's criticism. QM is clearly   
   flawed if one insists on wave function collapse. It's just completely   
   unfair to put the blame on entanglement, while the crime is committed   
   somewhere else!   
      
   > There IS something connecting the two   
   > detections, the question is where and how is this accomplished.   
      
   The answer is fully known! The propagation of the quantum state can   
   be computed (at least on a lattice) using quantum field theory as   
   we know it. You then get exactly those 'connecting' correlations in   
   the wave functional, or the state vector, or whatever you compute.   
   There is no ingredient missing, you have the full answer! As long   
   as you *don't* mess it up by trying to add the impossible: wave   
   function collapse..   
      
   > The problem is that experiments show a correlation between these two   
   > detection events   
      
   No they do not show any such thing! After the detection events, the   
   two detectors are in a superposition of having detected one or the   
   other polarization, and those detector superpositions are entangled,   
   just like the particles were before them. Nothing new has been   
   communicated between the sites.   
      
   This whole process is completely described by the well-know unitary   
   equations of QM. The basic example is to let the two entangled qubits   
   in their two distant places act as the control of two CNOT gates!   
   Afterwards the two target qubits of the CNOT gates are having the   
   entanglement. They have 'measured' the original two qubits and have   
   obtained an exact copy of their (entangled) spin states.   
      
   [NB: This 'ideal measurement' does not violate the no cloning theorem,   
   which may at first look surprising. The no cloning theorem does not   
   rule out a perfect measurement, as long as you meet the requirement of   
   having a 'prepared' target qubit, a 'blank' in a fixed spin state.]   
      
   >   ...    Bell's   
   > Inequality and the experiments based on it show that the statistics of   
   > these experiments implies that the second detection somehow knows what   
   > happened at the first detection.   
      
   Not at all, if 'detection' does what a CNOT gate does. You problem   
   only exists if you imagine the additional wave function collapse.   
   Which is not needed to explain any experiment. So leave it out!   
      
   --   
   Jos   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)