Quantum information distributors: Quantum network for symmetric and asymmetric cloning in arbitrary dimension and continuous limit

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Authors	BŮŽEK Vladimír BRAUNSTEIN S.L. HILLERY M.
Year of publication	2001
Type	Article in Periodical
Magazine / Source	Physical Review A
MU Faculty or unit	Faculty of Informatics
Citation
Field	Informatics
Keywords	quantum theory
Description	We show that for any Hilbert-space dimension, the optimal 1-->2 universal quantum cloner can be constructed from essentially the same quantum circuit, i.e., we find a universal design for universal cloners. In the case of infinite dimensions (which includes continuous variable quantum systems) the universal cloner reduces to an essentially classical device. More generally, we construct a universal quantum circuit for distributing qudits in any dimension which acts covariantly under generalized displacements and momentum kicks. The behavior of this covariant distributor is controlled by its initial state. We show that suitable choices for this initial state yield both universal cloners and optimized cloners for limited alphabets of states related by generalized phase-space displacements.
Related projects:	Informatics as the third methodology Non-sequential Models of Computing -- Quantum and Concurrent Distributed Models of Computing