Dynamics of a thermal entanglement in the not-resonant three-qubit Tavis–Cummings model with Kerr nonlinearity

In this article, we consider the dynamics of three identical qubits interacting not-resonantly with a thermal field of an ideal resonator with a Kerr medium. We have found the solutions of the Liouville quantum equation for the total density matrix of a system under consideration for the initial separable, biseparable, and genuine entangled states of the qubits and the thermal initial state of the resonator field. By averaging the total density matrix over the variables of the resonator field and the variables of one of the qubits, we found the reduced density matrix of the pair of remaining qubits. Two-qubit density matrices were used to calculate the qubit-qubit negativity. The results showed that detuning and Kerr nonlinearity can greatly enhance the amout of entanglement for initial separable state of a pair of qubits. It is also shown that detuning and a Kerr medium can inhibit the sudden death of entanglement.