Optimal universal and state-dependent quantum cloning

Dagmar Bruß, David P. DiVincenzo, Artur Ekert, Christopher A. Fuchs, Chiara Macchiavello, and John A. Smolin
Phys. Rev. A 57, 2368 – Published 1 April 1998
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Abstract

We establish the best possible approximation to a perfect quantum cloning machine that 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 teleportation scheme. We construct the optimal state-dependent cloners operating on any prescribed two nonorthogonal states and discuss their fidelities and the use of auxiliary physical resources in the process of cloning. The optimal universal cloners permit us to derive an upper bound on the quantum capacity of the depolarizing quantum channel.

  • Received 23 May 1997

DOI:https://doi.org/10.1103/PhysRevA.57.2368

©1998 American Physical Society

Authors & Affiliations

Dagmar Bruß1,4, David P. DiVincenzo2, Artur Ekert1, Christopher A. Fuchs3, Chiara Macchiavello1,4, and John A. Smolin2

  • 1Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
  • 2IBM Research Division, T.J. Watson Research Center, Yorktown Heights, New York 10598
  • 3Bridge Laboratory 12-33, California Institute of Technology, Pasadena, California 91125
  • 4ISI, Villa Gualino, Viale Settimio Severo 65, 10133 Torino, Italy

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Vol. 57, Iss. 4 — April 1998

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