This is of course the “EPR” paper, written with his colleagues Boris Podolsky and Nathan Rosen. Following a decade of vehement arguments with the great Neils Bohr about the meaning of quantum theory, this paper stands out as Einstein’s “parting shot” in the debate-his last ditch effort to prove that quantum mechanics could not be a fundamental theory. The paper-titled “Can quantum mechanical description of reality be considered complete?”-uses quantum mechanics to demonstrate that particles which interact in someway become entangled, in a loose sense meaning that their properties become correlated. As we’ll see in a moment, this is not an ordinary correlation in any sense of the word. It implies that there exists a strange connection between the particles that persists even when they are separated by great distances. In some sense, this connection is instantaneous, putting it in direct conflict with the special theory of relativity. It was this strange connection that led Einstein to the phrase “spooky action at a distance”.