Quantum recurrence: Everything goes back to the way it was

It is one of the most astonishing results of physics: when a complex system is left alone, it will return to its initial state with almost perfect precision. Gas particles, for example, chaotically swirling around in a container, will return almost exactly to their starting positions after some time. This "Poincaré Recurrence Theorem" is the foundation of modern chaos theory. For decades, scientists have investigated how this theorem can be applied to the world of quantum physics. Now, researchers at TU Wien (Vienna) have successfully demonstrated a kind of "Poincaré recurrence" in a multi-particle quantum system. The results have been published in the journal Science.