A lower bound on the relative error of mixed-state cloning and related operations
A E Rastegin · Journal of Optics B Quantum and Semiclassical Optics · 2003
We extend the concept of the relative error to mixed-state cloning and related physical operations, in which the ancilla contains some information a priori about the input state. The lower bound on the relative error is obtained. It is shown that this result provides further support for a stronger no-cloning theorem.