Thursday, July 12, 2007

EPR paradox - Wikipedia, the free encyclopedia:

Although originally devised as a thought experiment that would demonstrate the incompleteness of quantum mechanics, actual experimental results refute the principle of locality, invalidating the EPR trio's original purpose. The "spooky action at a distance" that so disturbed the authors of EPR consistently occurs in numerous and widely replicated experiments. Einstein never accepted quantum mechanics as a "real" and complete theory, struggling to the end of his life for an interpretation that could comply with relativity without implying "God playing dice", as he condensed his dissatisfaction with quantum mechanics's intrinsic randomness and counter-intuitivity.

The EPR paradox is a paradox in the following sense: if one takes quantum mechanics and adds some seemingly reasonable conditions (referred to as locality, realism, counter factual definiteness, and completeness), then one obtains a contradiction. However, quantum mechanics by itself does not appear to be internally inconsistent, nor — as it turns out — does it contradict relativity. As a result of further theoretical and experimental developments since the original EPR paper, most physicists today regard the EPR paradox as an illustration of how quantum mechanics violates classical intuitions.