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Strathprints serves world leading Open Access research by the University of Strathclyde, including research by the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS), where research centres such as the Industrial Biotechnology Innovation Centre (IBioIC), the Cancer Research UK Formulation Unit, SeaBioTech and the Centre for Biophotonics are based.

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Strategies and networks for state-dependent quantum cloning

Chefles, Anthony and Barnett, Stephen M. (1999) Strategies and networks for state-dependent quantum cloning. Physical Review A, 60 (1). pp. 136-144. ISSN 1094-1622

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Abstract

State-dependent cloning machines that have so far been considered either deterministically copy a set of states approximately or probablistically copy them exactly. In considering the case of two equiprobable pure states, we derive the maximum global fidelity of N approximate clones given M initial exact copies, where N>M. We also consider strategies that interpolate between approximate and exact cloning. A tight inequality is obtained that expresses a trade-off between the global fidelity and success probability. This inequality is found to tend, in the limit N → ∞, to a known inequality that expresses the trade-off between error and inconclusive result probabilities for state-discrimination measurements. Quantum-computational networks are also constructed for the kinds of cloning machine we describe. For this purpose, we introduce two gates: the distinguishability transfer and state separation gates. Their key properties are described and we show how they may be decomposed into basic operations.