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Dynamics of Quantum Fisher information in a spin-boson model

Quantum Fisher information characterizes the phase sensitivity of qubits in the spin-boson model with a finite bandwidth spectrum. In contrast with Markovian reservoirs, the quantum Fisher information will flow from the environments to qubits after some times if the bath parameter $s$ is larger than a critical value which is related to temperatures. The sudden change behavior will happen during the evolution of the quantum Fisher information of the maximal entanglement state in the non-Markovian environments. The sudden change times can be varied with the change of the bath parameter $s$. For a very large number of entangled qubits, the sudden change behavior of the maximal quantum Fisher information can be used to characterize the existence of the entanglement. The metrology strategy based on the quantum correlated state leads to a lower phase uncertainty when compared to the uncorrelated product state.