We investigate the eect of eld changing on two qubit entanglement. We choose the coherent state, the cat state and the squeezed state as dierent states of interacting eld with atom. The correlation between two qubits can be degraded by environmental noise, this phenomenon has been labelled sudden death of entanglement. The double JaynesCummings model as a solvable model is used for describing the dynamic of sudden death of entanglement. We measure two-qubit entanglement using the concurrence and the negativity. The Fisher information is introduced, too, and compares results with previous entanglement measures. Finally we conclude that the Fisher information is not an entanglement measure.
