N. David Mermin

The quantum correlations between spatially separated systems that were formerly in close contact but no longer interact, can have a mysterious quality, captured by the phrase "quantum nonlocality". Attitudes toward this "nonlocality" vary from the view that nothing is nonlocal except the misguided attempt to explain the correlations in terms of nonexistent "hidden variables", to the view that quantum mechanics has proved that what you decide to do over here can instantaneously alter the physical character of something over there. Such conceptually mysterious correlations have assumed a central role in quantum information theory. While the philosophical puzzles do not hinder the gedanken-practical application of the correlations, quantum information scientists might bear the puzzles in mind, on the chance that some of the exquisitely clever things they manage to do with entangled states might illuminate them.