parallel_prankster writes: Physicists have, for the first time, demonstrated in an experiment that the decision whether two particles were in an entangled or in a separable quantum state can be made even after these particles have been measured and may no longer exist. Entangled particles exhibit correlations which are stronger and more intricate than those allowed by the laws of classical physics. If two particles are in an entangled quantum state, they have perfectly defined joint properties at the expense of losing their individual properties. This is like having two dice which have no orientation until they are subject to measurement, upon which they certainly show the same (random) side up. In contrast, so-called separable quantum states allow for a classical description, because every particle has well-defined properties on its own. Two dice, each one of them with its own well-defined orientation, are in a separable state. Now, one would think that at least the nature of the quantum state must be an objective fact of reality. Either the dice are entangled or not. Zeilinger's team has now demonstrated in an experiment that this is not always the case. Free abstract along with the choice to pay for the full paper can be found on the nature website
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