Superbroadcasting of mixed states

Phys Rev Lett. 2005 Aug 5;95(6):060503. doi: 10.1103/PhysRevLett.95.060503. Epub 2005 Aug 5.

Abstract

We derive the optimal universal broadcasting for mixed states of qubits. We show that the no-broadcasting theorem cannot be generalized to more than a single input copy. Moreover, for four or more input copies it is even possible to purify the input states while broadcasting. We name such purifying broadcasting superbroadcasting.