  A scheme is proposed to estimate the system and environmental parameter, the
detuning, temperature and the squeezing strength with a high precision by the
two-level atom system. It hasn't been reported that the squeezing strength
estimation through quantum Fisher information. We find entangled state and
optimal superposition state are beneficial for parameter estimation with
one-qubit probe by calculating quantum Fisher information and fidelity. And the
fidelity between initial and final states of the atom can be improved via the
two-qubit probe. Moreover, the phenomenon of quantum Fisher information return
occurs when the detuning or the temperature is estimated. Our work provides a
basis for precision measurement technology and quantum information processing.
