The European Physical Journal D

, Volume 59, Issue 3, pp 521–523 | Cite as

Parameter estimation with mixed quantum states

Quantum Information

Abstract.

We consider quantum enhanced measurements with initially mixed states. We show very generally that for any linear propagation of the initial state that depends smoothly on the parameter to be estimated, the sensitivity is bound by the maximal sensitivity that can be achieved for any of the pure states from which the initial density matrix is mixed. This provides a very general proof that purely classical correlations cannot improve the sensitivity of parameter estimation schemes in quantum enhanced measurement schemes.

Keywords

Entangle State Mixed State Pure State Separable State Classical Correlation 

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Copyright information

© EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2010

Authors and Affiliations

  1. 1.Université de Toulouse, UPS, Laboratoire de Physique Théorique (IRSAMC)ToulouseFrance
  2. 2.CNRS, LPT (IRSAMC)ToulouseFrance

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