In 1935, Albert Einstein discovers an amazing property of quantum mechanics, entanglement, which seems to conflict with his local realist world view, unless one admits that quantum mechanics is an incomplete theory. This will lead to a hot debate with Niels Bohr, settled only after the death of the two giants, with the discovery by John Bell of the inequalities named after him, and the experiments stimulated by Bell's breakthrough.

We know nowadays that even at a separation of tens of kilometers, two entangled photons keep the extraordinary behavior that Einstein had pointed out. This is an important fact for our understanding of the world, but moreover it has become a new tool allowing the development of the new field of quantum information. * Alain Aspect won the 2005 Gold Medal from CRNS. You may check out that story at this link: http://www2.cnrs.fr/en/394.htm