paper

Asymmetric quantum cloning machines in any dimension

arXiv:quant-ph/9805024 · doi:10.1080/09500340008244036

Abstract

A family of asymmetric cloning machines for -dimensional quantum states is introduced. These machines produce two imperfect copies of a single state that emerge from two distinct Heisenberg channels. The tradeoff between the quality of these copies is shown to result from a complementarity akin to Heisenberg uncertainty principle. A no-cloning inequality is derived for isotropic cloners: if and are the depolarizing fractions associated with the two copies, the domain in -space located inside a particular ellipse representing close-to-perfect cloning is forbidden. More generally, a no-cloning uncertainty relation is discussed, quantifying the impossibility of copying imposed by quantum mechanics. Finally, an asymmetric Pauli cloning machine is defined that makes two approximate copies of a quantum bit, while the input-to-output operation underlying each copy is a (distinct) Pauli channel. The class of symmetric Pauli cloning machines is shown to provide an upper bound on the quantum capacity of the Pauli channel of probabilities , and .

18 pages RevTeX, 3 Postscript figures; new discussion on no-cloning uncertainty relations, several corrections, added references

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