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This article misses the point about quantum correlation. The historical context first: When von Neumann attempted to prove the non-existence of hidden variables, he referred to variances and various properties of observables assuming that they made sense generally even for non-commuting observables. You make no reference to this at all nor to the relation of correlation to measurement which is an essential point in understanding why von Neumann's proof was wrong.
Moreover you only refer to quantum correlation for a Bell test setup. This needs to be handled for much more general pairs of observables. CSTAR 23:05, 24 Jan 2005 (UTC)
I revised this page late last night and am not sure I've got it right. I found myself inevitably beginning to transform it into a page on the detection loophole. The point is that the local realist formula can cover null outcomes easily, but the QM one (which I probably should have given as well) is only intended for the case where all outcomes are +1 or -1. The only way of making the QM theory apply to experiments with inefficient detectors is to assume that we can take just the set of coincidences and treat these as if they were the set of emitted pairs. In other words, we are forced to assume "fair sampling". This is why the separate definition of "quantum correlation" is important. When there are no null results, because the mean on each side is (under rotational invariance) zero and because all results have absolute value 1, the definition coincides with the ordinary one. When there are some null values, the difference become critical. [This para is copied from the "Bell's theorem" talk page.] Caroline Thompson 08:30, 26 July 2005 (UTC)
I think this article misses the point. Quantum Discord , Quantum work deficit on SEPARABLE states are also quantum correlations ... Not only Bell type violations are quantum ...
This article is rated Stub-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||
|
This article misses the point about quantum correlation. The historical context first: When von Neumann attempted to prove the non-existence of hidden variables, he referred to variances and various properties of observables assuming that they made sense generally even for non-commuting observables. You make no reference to this at all nor to the relation of correlation to measurement which is an essential point in understanding why von Neumann's proof was wrong.
Moreover you only refer to quantum correlation for a Bell test setup. This needs to be handled for much more general pairs of observables. CSTAR 23:05, 24 Jan 2005 (UTC)
I revised this page late last night and am not sure I've got it right. I found myself inevitably beginning to transform it into a page on the detection loophole. The point is that the local realist formula can cover null outcomes easily, but the QM one (which I probably should have given as well) is only intended for the case where all outcomes are +1 or -1. The only way of making the QM theory apply to experiments with inefficient detectors is to assume that we can take just the set of coincidences and treat these as if they were the set of emitted pairs. In other words, we are forced to assume "fair sampling". This is why the separate definition of "quantum correlation" is important. When there are no null results, because the mean on each side is (under rotational invariance) zero and because all results have absolute value 1, the definition coincides with the ordinary one. When there are some null values, the difference become critical. [This para is copied from the "Bell's theorem" talk page.] Caroline Thompson 08:30, 26 July 2005 (UTC)
I think this article misses the point. Quantum Discord , Quantum work deficit on SEPARABLE states are also quantum correlations ... Not only Bell type violations are quantum ...