  In this contribution, quantum Fisher information is utilized to estimate the
parameters of a central qubit interacting with a single-spin qubit. The effect
of the longitudinal, transverse and the rotating strengths of the magnetic
field on the estimation degree is discussed. It is shown that, in the resonance
case, the number of peaks and consequently the size of the estimation regions
increase as the rotating magnetic field strength increases. The precision
estimation of the central qubit parameters depends on the initial state
settings of the central and the spin- qubit, either encode classical or quantum
information. It is displayed that, the upper bounds of the estimation degree
are large if the two qubits encode classical information. In the non-resonance
case, the estimation degree depends on which of the longitudinal/transverse
strength is larger. The coupling constant between the central qubit and the
spin- qubit has a different effect on the estimation degree of the weight and
the phase parameters, where the possibility of estimating the weight parameter
decreases as the coupling constant increases, while it increases for the phase
parameter. For large number of spin-particles, namely, we have a spin-bath
particles, the upper bounds of the Fisher information with respect to the
weight parameter of the central qubit decreases as the number of the spin
particle increases. As the interaction time increases, the upper bounds appear
at different initial values of the weight parameter.
