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arXiv · quant-ph/9705038

Optimal Universal and State-Dependent Quantum Cloning

D. Bruss·D. P. DiVincenzo·A. Ekert·C. A. Fuchs·C. Macchiavello·J. A. Smolin
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Abstract

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.

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D. Bruss, D. P. DiVincenzo, A. Ekert, C. A. Fuchs, C. Macchiavello, J. A. Smolin. 1997-12-06. Optimal Universal and State-Dependent Quantum Cloning. https://doi.org/10.1103/physreva.57.2368

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