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arXiv · quant-ph/9812035

Strategies and Networks for State-Dependent Quantum Cloning

Anthony Chefles·Stephen M. Barnett
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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 which interpolate between approximate and exact cloning. A tight inequality is obtained which expresses a trade-off between the global fidelity and success probability. This inequality is found to tend, in the limit as $N{\to}{\infty}$, to a known inequality which 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

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Anthony Chefles, Stephen M. Barnett. 1998-12-15. Strategies and Networks for State-Dependent Quantum Cloning. https://doi.org/10.1103/physreva.60.136

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