Operational meaning of the classical fidelity and the path length in Fisher-Kubo-Mori-Bogoliubov geometry

Abstract: We show that the minimum entropy production in near-reversible quantum state transport along a path is simple function of the path length measured according to the Fisher-KMB metrics. Hence the sharp values of path lengths, also called statistical lengths, obtain operational meaning to quantify the residual irreversibility in near-reversible state transport. In the classical limit, the Bhattacharyya fidelity obtains a sharp operational meaning after eighty years.