Quantum estimation by local observables
- Department of Physics, Faculty of Science, Tohoku University, Sendai, 980-8578 (Japan)
- Graduate School of Information Sciences, Tohoku University, Sendai, 980-8579 (Japan)
Quantum estimation theory provides optimal observations for various estimation problems for unknown parameters in the state of the system under investigation. However, the theory has been developed under the assumption that every observable is available for experimenters. Here, we generalize the theory to problems in which the experimenter can use only locally accessible observables. For such problems, we establish a Cramer-Rao-type inequality by obtaining an explicit form of the Fisher information as a reciprocal lower bound for the mean-square errors of estimations by locally accessible observables. Furthermore, we explore various local quantum estimation problems for composite systems, where nontrivial combinatorics is needed for obtaining the Fisher information.
- OSTI ID:
- 20645872
- Journal Information:
- Physical Review. A, Vol. 70, Issue 2; Other Information: DOI: 10.1103/PhysRevA.70.022327; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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