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Quantum Estimation of Open Systems Using Extended Cramer-Rao Bounds

Mehboudi, Mohammad | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45247 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Rezakhani, Ali; Alipour, Sahar
  7. Abstract:
  8. Any physical system is characterized with some set of quantities or parameters, knowing which, is equivalent to estimation of the system. Evaluating such parameters is usually done using tomography methods. An important question to ask, is how to increase the precision of measurement, being able to do some specific set of physical operations, say, measurement?
    this question is more important in parameter estimation in quantum meanical systems. It has been shown that, quantum meanics causes a fundamental limit, on precision of estimating su parameters, escribed by the so called “antum Cramér-Rao bound”.We must note that almost all quantum meanical systems are interacting with the environment
    surrounding them. Su unavoidable interactions cause decoherency in quantum systems. Obviously, decoherence has its own effects on the precision of estimation, due to the interaction with the environment and loosing some information. e aim in su systems is, to reformulate the bound on precision, considering the important role of environment. Recently, at least two general models have been proposed, to do parameter estimation in open systems, one of whi is based on our group’s work in Sharif University of Tenology. In this method, a framework has been introduced, in whi the quantum Cramér-Rao bound is inferred in a simpler way (than the previous method) and is similar to the familiar case of closed systems. Providing the opportunity to investigate-more directly- the role of quantum and classical correlations, in parameter estimation, is another advantage of this method.In this thesis, beside revision and improvement of our own method, for some specific open systems (together with practical examples) we have investigated how it is possible to measure the precision of parameters
  9. Keywords:
  10. Quantum Estimation ; Cramer-Rao Bound ; Estimators ; Estimation Error ; Measurement

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