28 - Physics 6210/Spring 2007/Lecture 28 Lecture 28...

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Physics 6210/Spring 2007/Lecture 28 Lecture 28 Relevant sections in text: § 3.9 Spin correlations and quantum weirdness: The EPR argument Recall the results of adding two spin 1/2 angular momenta. The fact that the total spin magnitude is not compatible with the individual spin observables leads to some somewhat dramatic consequences, from a classical physics point of view. This drama was already noted by Einstein-Podolsky and Rosen (EPR) in a famous critique of the completeness of quantum mechanics. Much later, Bell showed that the basic “classical locality” assumption of EPR must be violated, implying in effect that nature is truly as weird as quantum mechanics makes it out to be. Here we give a brief discussion of some of these ideas. The original EPR idea did not deal with spins, but with a pair of spinless particles. We shall in a moment, following Bohm, deal with a spin system. But it is worth first describing the EPR argument, which goes as follows. Consider two spinless particles characterized
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This note was uploaded on 02/18/2012 for the course PHYSICS 6210 taught by Professor M during the Spring '07 term at AIU Online.

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