In this Letter, we present two analytic expressions that most generally simulate n-qubit controlled-U gates with standard one-qubit gates and CNOT gates using exponential and polynomial complexity respectively. Explicit circuits and general expressions of decomposition are derived. The exact numbers of basic operations in these two schemes are given using gate counting technique.
@article{arxiv.0708.3274,
title = {Analytic Constructions of General n-Qubit Controlled Gates},
author = {Yang Liu and Gui Lu Long and Yang Sun},
journal= {arXiv preprint arXiv:0708.3274},
year = {2007}
}