Tests of Nonlocality

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Quantum mechanics, though one of the most successful and fundamental theories in physics, encompasses phenomena at odds with our intuition. Most notable is the phenomenon of entanglement, which violates the fundamental classical assumptions of locality and realism, which respectively state that objects which are far apart do not instantaneously interact and that a description of the universe can exist which will predict the outcome of any experiment.

At our lab, using a source of entangled photons, we are able to make a series of measurements which manifestly violate these assumptions, and therefore validate the quantum mechanical world-view. (The catch is that some assumptions go into these tests, leaving loopholes for local-realistic theories. Groups around the world, including this one, are currently working towards a loophole-free test which would finally vindicate the reality of quantum nonlocality.)