Eur. Phys. J. D (2014) 68: 170
https://doi.org/10.1140/epjd/e2014-50047-1

Regular Article

Optimal quantum channel estimation of two interacting qubits subject to decoherence

¹ Beijing Computational Science Research Center, Beijing 100084, P.R. China
² School of Mathematics and Computer Science, Guizhou Normal University, Guiyang 550001, P.R. China
³ Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, P.R. China

^a e-mail: qzhengnju@gmail.com

Received: 16 January 2014
Received in final form: 24 March 2014
Published online: 27 June 2014

Abstract

We investigate the estimation of the quantum channel parameter for a two-qubit system with each qubit independently interacting with its Markovian environment. The dynamics of quantum Fisher information in this system is studied and employed as a measure to quantify the precision of the estimation. We find that the dynamic behavior of quantum Fisher information with respect to the decoherence rate γ is proportional to t²/[exp(γt) − 1] and exp(−2γt) in the unitary limit and the completely decoherent limit, respectively. We also study the evolution of quantum Fisher information with respect to the interaction strength, which shows oscillating behavior. Furthermore, we show that the increase in entanglement of the input state may not enhance the precision of quantum estimation.