Abstract
We present quantum cloning machines that transform identical qubits into identical copies and we prove that the fidelity (quality) of these copies is optimal. The connection between cloning and measurement is discussed in detail. When the number of clones tends towards infinity, the fidelity of each clone tends towards the optimal fidelity that can be obtained by a measurement on the input qubits. More generally, quantum cloning machines are universal devices to translate quantum information into classical information.
- Received 27 May 1997
DOI:https://doi.org/10.1103/PhysRevLett.79.2153
©1997 American Physical Society