Quantum theory: A loophole-free bell test

Quantum theory predicts that the observation of one object can affect another at that very moment, even if it is at the other end of the universe, a phenomenon that Einstein did not believe in. But it has just been achieved that two electrons, separated 1.3 kilometers on the campus of the Technical University of Delft (Netherlands), communicate 'invisibly' and instantaneously. The breakthrough, in which the Institute of Photonic Sciences of Barcelona has participated, can be applied in quantum cryptography, but also confirms how strange our universe is.