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In mathematics, in the area of quantum information geometry, the Bures metric〔D. Bures, (1969) ''Trans. Am. Math. Soc.'' 135, p.199.〕 or Helstrom metric〔C.W. Helstrom, (1967) "Minimum mean-squared error of estimates in quantum statistics", ''Phys. Lett.'' A 25 pp.101-102.〕 defines an infinitesimal distance between density matrix operators defining quantum states. It is a quantum generalization of the Fisher information metric, and is identical to the Fubini–Study metric〔Paolo Facchi, Ravi Kulkarni, V. I. Man'ko, Giuseppe Marmo, E. C. G. Sudarshan, Franco Ventriglia "(Classical and Quantum Fisher Information in the Geometrical Formulation of Quantum Mechanics )" (2010), ''Physics Letters'' A 374 pp. 4801. DOI: 10.1016/j.physleta.2010.10.005〕 when restricted to the pure states alone. ==Definition== The metric may be defined as : where is Hermitian 1-form operator implicitly given by : Some of the applications of the Bures metric include that given a target error, it allows the calculation of the minimum number of measurements to distinguish two different states and the use of the volume element as a candidate for the Jeffreys prior probability density for mixed quantum states. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bures metric」の詳細全文を読む スポンサード リンク
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