Relative error of state-dependent cloning
Alexey Eduardovich Rastegin · Physical Review A · 2002
We present a criterion for estimation of the quality of state-dependent $\stackrel{\ensuremath{\rightarrow}}{N}L$ cloning. We call this criterion the relative error because one compares the errors in copies with contiguous size, which is not independent of the closeness of the states to be copied. First, we prove several useful statements that maintain the interpretation for the proposed measure. The tightest lower bound on the relative error is then derived. We describe the optimal asymmetric state-dependent cloner that minimizes the relative error.