  The efficiency of parameter estimation of quantum channels is studied in this
paper. We introduce the concept of programmable parameters to the theory of
estimation. It is found that programmable parameters obey the standard quantum
limit strictly; hence no speedup is possible in its estimation. We also
construct a class of non-unitary quantum channels whose parameter can be
estimated in a way that the standard quantum limit is broken. The study of
estimation of general quantum channels also enables an investigation of the
effect of noises on quantum estimation.
