Nonunital non-Markovian dynamics induced by a spin bath and interplay of quantum Fisher information

TL;DR

This paper investigates how nonunital non-Markovian dynamics, induced by a spin bath, affect quantum Fisher information and parameter estimation, revealing controllable effects that can enhance quantum metrology.

Contribution

It introduces a detailed analysis of nonunital non-Markovian effects on quantum Fisher information and demonstrates controllability via magnetic field and temperature.

Findings

Nonunital effects influence quantum Fisher information growth.

Revival phenomena observed in fidelity angles.

Controllability of nonunitality through external parameters.

Abstract

We explore the nonunital non-Markovian dynamics of a qubit immersed in a spin bath. The nonunital environmental effects on the precisions of quantum parameter estimation are investigated. The time-dependent transfer matrix and inhomogeneity vector are obtained for the description of the open dynamical process. The evolution of the coherent vectors for a qubit is studied so as to geometrically demonstrate the nonunital non-Markovian effects. The revivals of angles for the fidelity between a maximal mixed state and an arbitrary trajectory state are presented in the nonunital non-Markovian dynamics. The degree for the nonunitality is controllable with the changes of the local magnetic field for a qubit and spin bath temperature. It is found out that the increase of quantum Fisher information for composite states is connected with the nonunital non-Markovian effects, which is helpful for the improvement of quantum metrology.