Optimal cloning with respect to the relative error
arXiv:0906.5494
Abstract
The relative error of cloning of quantum states with arbitrary prior probabilities is considered. It is assumed that the ancilla may contain some a priori information about the input state to be cloned. The lower bound on the relative error for general cloning scenario is derived. Both the case of two-state set and case of multi-state set are analyzed in details. The treated figure of merit is compared with other optimality criteria. The quantum circuit for optimal cloning of a pair of pure states is constructed.
9 pages, 2 figures, 1 table. Major changes. New section in which different criteria are compared is added. The bibliography is recast