Dynamical decoupling-assisted quantum parameter estimation with initial system-environment correlations

Abstract

Decoherence is the main obstacle to quantum precision measurement. One must adopt appropriate control strategies to suppress decoherence. In this paper, we study the dephasing model of the system-environment with initial correlation, and use the quantum Fisher information (QFI) as the tool to explore the effect of dynamical decoupling pulses on inhibiting decoherence and improving the estimation precision of quantum parameters. We firstly study the influence of the initial correlations and initial quantum state on the dynamical evolution of a single qubit in this mode. Based on numerical calculations, in the Ohmic and the super-Ohmic thermal reservoir, we find that the periodic dynamical decoupling (PDD) sequence can significantly reduce the amplitude of the decoherence function, except for the "anti-Zeno" effect when the number of pulses is relatively small. By a judicious choice of the PDD pulse frequency, the dynamical decoupling pulses can effectively enhance the precision of quantum parameter estimation. And due to the peak structure existing in the decoherence function, the effect of applying Uhrig dynamical decoupling (UDD) sequence on the model is not ideal.