title: Optimal measurement on noisy quantum systems.
abstract: We identify the optimal measurement for obtaining information about the original quantum state after the state to be measured has undergone partial decoherence due to noise. We quantify the information that can be obtained by the measurement in terms of the Fisher information and find its value for the optimal measurement. We apply our results to a quantum control scheme based on a spin-boson model.
authors.affiliation: Department of Physics, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Takahiro
authors.initials: T
authors.lastname: Sagawa
authors.forename: Masahito
authors.initials: M
authors.lastname: Ueda