Optimal Universal and State-Dependent Quantum Cloning

Journal article

We establish the best possible approximation to a perfect quantum cloning machine which produces two clones out of a single input. We analyze both universal and state-dependent cloners. The maximal fidelity of cloning is shown to be 5/6 for universal cloners. It can be achieved either by a special unitary evolution or by a novel teleportation scheme. We construct the optimal state-dependent cloners operating on any prescribed two non-orthogonal states, discuss their fidelities and the use of auxiliary physical resources in the process of cloning. The optimal universal cloners permit us to derive a new upper bound on the quantum capacity of the depolarizing quantum channel.

Authors: Bruss, D; DiVincenzo, D; Ekert, A; Fuchs, C; Macchiavello, C

• Publication status: Published
• Journal: PRA
• Volume: 57
• Issue: 4
• Pages: 2368
• Publication date: 1997-05-22
• DOI: 10.1103/PhysRevA.57.2368
• EISSN: 1094-1622
• ISSN: 1050-2947
• Keywords: quant-ph