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"Spooky action-at-a-distance" with individual atoms By: Christopher Monroe

Summary: "Spooky action-at-a-distance" with individual atoms
By: Christopher Monroe
Albert Einstein never liked Quantum Mechanics, with its fuzzy superpositions and
confused states of reality. In 1935, he and colleagues Boris Podolsky and Nathan Rosen
proposed a thought experiment that they believed would finally show cracks in the new
quantum theory. The essentials of their famed proposal can be seen by cconsidering two
"quantum coins," that are prepared in a strange superposition of being both heads-up and
both tails-up at the same time. When such coins are brought far apart from each other and
then measured, quantum mechanics predicts that the only possible results can be HH and
TT the orientation of the coins always matches in perfect correlation. But when either
individual coin is observed, its value is expected to be totally random (H or T). What's
interesting here is that while an individual coin is in an indeterminate state until observed,
the observer immediately knows that orientation of the other coin, and this knowledge
happens faster than the speed of light can traverse the
distance between the coins.
Einstein called this quantum behavior "spooky action-
at-a-distance," and concluded that either quantum
mechanics is incomplete, or it is just very weird. We
now know, thanks to John Bell in 1964, that if quantum
mechanics is indeed incomplete, than any more


Source: Anisimov, Mikhail - Institute for Physical Science and Technology & Department of Chemical Engineering and Biomolecular Engineering, University of Maryland at College Park


Collections: Physics; Materials Science