Distance measures to compare real and ideal quantum processes
Alexei Gilchrist, Nathan K. Langford, Michael A. Nielsen · Physical Review A · 2005
With growing success in experimental implementations it is critical to identify a ``gold standard'' for quantum information processing, a single measure of distance that can be used to compare and contrast different experiments. We enumerate a set of criteria that such a distance measure must satisfy to be both experimentally and theoretically meaningful. We then assess a wide range of possible measures against these criteria, before making a recommendation as to the best measures to use in characterizing quantum information processing.