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pat devine

- 9

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For the next bit its important to understand the Gedankenexperiment:

Two spin one half particles are in a singlet state. Each of the pairs spins are measured by two distant apparatus. Each apparatus is such that it allows two possible measurements -

-A random measurement (each of the apparatus can make an independent spin measurement ie each different than the other) and

-A fixed measurement. ( both apparatus have a setting fixed at say 30 degree)The inequality is then constructed using the very crucial assumption that measurements made along the fixed axis are negatively correlated. ie when A measures up B measures down. In the non quantum world we can assume this to be correct even when no measurement is made. Hence we can essentially measure each particle twice, once along the random axis and then again along the fixed axis - but we don't actually measure along the fixed axis we just know what the outcome of the correlation will be. However we can not assume this to be true in the quantum world. Each particle can be measured only once by each apparatus, not twice and within the derivation it is assumed that this is possible. It is a subtle point that I haven't seen any discussion of. To sum up, that Bells inequality is violated by quantum experiments is merely due to the fact that it is not appropriate for quantum systems and therefore its violation reveals nothing more than the fact that two concurrent measurements of spin are not possible on the same particle at the same time. Rather than the current interpretation that it somehow invokes the reality of non locality. If the inequality is modified in such a manner as to allow for a distinct and separate measurement of a particle along the fixed axis/setting, then another pair of particles is required which dilutes the expectation values and would likely result in an inequality which is consistent with QM.

Regards

P