Quantum replication at the Heisenberg limit.

No process in nature can perfectly clone an arbitrary quantum state. But is it possible to engineer processes that replicate quantum information with vanishingly small error? Here we demonstrate the possibility of probabilistic super-replication phenomena where N equally prepared quantum clocks are transformed into a much larger number of M nearly perfect replicas, with an error that rapidly vanishes whenever M is small compared with N(2). The quadratic replication rate is the ultimate limit imposed by quantum mechanics to the proliferation of information and is fundamentally linked with the Heisenberg limit of quantum metrology.