Quantum Fisher Information of Two Moving Four-Level Atoms

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We investigate dynamics of quantum entanglement (QE) and quantum Fisher information (QFI) of a system of two four-level atoms moving in the thermal environment. The time evolution of the state vector of the whole quantum system interacting with the thermal field is investigated numerically in the presence of intrinsic decoherence (ID). We see that ID and the thermal environment play a prominent role in the time evolution of the quantum system. QFI and von Neumann entropy (VNE) show the opposite response during their time evolution in the presence of the thermal environment. QFI is seen as more prone to intrinsic decoherence when compared with the VNE in the presence of the thermal environment. VNE changes remarkably with increase in the intrinsic decoherence parameter without the atomic motion. However, the periodic response of VNE is seen because of the atomic motion which gets modest under environmental effects. The decay of VNE is further damped at larger time scales that confirm that ID affects the system dynamics in a thermal environment. Moreover, VNE and QFI saturate to a lower level for larger time-scales under these environments. The damping response of VNE is observed under intrinsic decoherence for larger time scales. The VNE and QFI saturate to a lower level for larger time scales under the environmental effects. Moreover, one sees that the thermal environment induces a quicker decay of VNE when compared with the decay induced by ID. In this manner, the ID and thermal environment are found to suppress the nonclassical effects of the quantum system.