FrediFizzx wrote:minkwe wrote:A genuine CHSH test experiment has never been performed (loopholes are a red-herring, even if all loopholes are assumed closed, this statement will still be true). All experiments so far have been testing QM not CHSH.
Hmm... I suspect you are missing something from the opposite direction of what Richard is missing. Or there is something very subtle in CHSH that I am missing. I believe CHSH was specifically designed for an Aspect or Weihs, et al, type of experiment where two angles are randomly selected for A and B per particle pair. I do believe it works for that and has been violated in those kinds of experiments sans any loopholes.
We are talking about experiments designed to discriminate between QM and LR, which make different predictions concerning correlations E(a, b) between two binary outcomes, depending on two settings a and b, which are directions in space.
Clauser, Horne, Shimony and Holt proposed an experiment, generalising/improving an experiment proposed by Bell.
Aspect, Weihs and others, performed it.
The CHSH idea is to focus on just four of the correlations. We consider a clever choice of directions a1, a2, b1, b2; and look at E(a1, b1), E(a1, b2), E(a2, b1) and E(a2, b2). Under QM the four correlations can be +/-0.7, under local realism they could be maximally +/-0.5; with in both cases, the same pattern, three positive and one negative, or the other way round.
The CHSH experiment was a clever generalization of Bell's experiment which had a1 = b1 and insisted that E(a1, b1) = -1. The CHSH experiment is easier to do and easier for QM to win, than the Bell experiment. In real life experiments you won't find *perfect* anticorrelation at equal settings, so the experiment would always fail.
In all of these classical experiments, for each pair of particles, one measurement only is done on each particle.
Two important things make the experiment loophole free.
(1) For each run, the settings are chosen randomly and independently of everything else. So if there are N runs, there will be about N/4 with each of the four measurement setting pairs. Disjoint.
(2) Each run generates two binary outcomes +/- 1
Now in Joy's experimental papers Joy describes how the directions of spin of two objects will be determined by computer analysis of video movies, resulting in two directions s_k and - s_k, k=1, ..., N. *Given* these two directions, the outcomes of measurements with settings a and b are sign(a . s_k) and sign(b . - s_k) respectively. So this is a major departure from quantum optics measurements where two "black boxes" generates two binary outcomes given two settings (they are both fed information from another "black box", the source). In Joy's experiment we *measure the hidden variables* s_k and - s_k and then *compute* the two binary outcomes. There is only one huge "black box", and out of the black box comes s_k and -s_k.
So it would be perfectly feasible to calculate A(a, b) on all N runs, as well as to calculate it for a random sample of about one quarter of all N runs.
Joy said he was completely indifferent to this choice and
I am fairly indifferent too: if the measurement settings are chosen by tossing fair coins (altogether N x 2 times) and N is decently large (e.g. 10 000) there won't be much difference.
I am prepared to bet
on the outcome of Joy's experiment, as described in Joy's experimental paper. If he wants to *change* the description of the experiment, then the bet has to be re-negotiated; maybe it has to be called off.
Note that Michel's epr-simple computer programs, and my modification of it leading to the current favourite, the Pearle model, can be considered simulations of Joy's experiment, in that the hidden variable, directions s_k and - s_k, are *generated* by some (pseudo) random procedure, and only after that, outcomes sign(a . s_k) and sign(b . - s_k) are *computed*. Michel imposes this separation of these two stages very elegantly with one program computing the s_k's and a different program computing the outputs given the settings.
In both Michel's and Pearle's programs there is however an extra ingredient: a further test is done ensuring that, depending on the settings a and b, some runs k are rejected.