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Degree of Entanglement Through the Von-Neumann Entropy for An N-type Four-level Atom Interacting with a Single-mode Field with Nonlinearities
A. A. Eied

The evolution of the atomic quantum entropy and the atom-field entanglement in a system of a N-configuration four-level atom interacting with a single-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom-field coupling through the von-Neumann entropy will be investigated. With the derivation of the unitary operator within the frame of the dressed state and the exact results for the state of the system we perform a careful investigation of the temporal evolution of the entropy. A factorization of the initial density operator is assumed, considering the field to be initially in coherent state and the atom initially in its most upper excited state. The effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy will be analyzed.

Keywords: Entanglement, Four-level atom, von-Neumann entropy

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