Eur. Phys. J. D (2016) 70: 8
https://doi.org/10.1140/epjd/e2015-60460-5

Regular Article

Invertible condition of quantum Fisher information matrix for a mixed qubit

¹ School of Mathematics and Computer Science, Guizhou Normal University, Guiyang 550001, P.R. China
² School of Biology and Engineering, Guizhou Medical University, Guiyang 550001, P.R. China
³ Division of Quantum Physics and Quantum Information, Beijing Computational Science Research Center, Beijing 100084, P.R. China

^a e-mail: qz@csrc.ac.cn

Received: 6 August 2015
Received in final form: 16 November 2015
Published online: 14 January 2016

Abstract

Estimating multiparamter simultaneously as precise as possible is an important goal of quantum metrology. As a first step to this end, here we give a condition determining whether two arbitrary parameters can be estimated simultaneously for a qubit in the mixed state. An application of this condition is shown.