Dynamics of thermal pairwise entanglement of qubits in the three-qubit Tavis–Cummings model

An exact solution has been found for a model consisting of three identical qubits, one of which is in a free state, and the other two are trapped in an ideal cavity and resonantly interact with the selected mode of this cavity. Based on the exact solution, the pairwise negativities of qubits was calculated for two initial W-type qubits states and the thermal state of the cavity field. The influence of the intensity of the thermal noise of the cavity and the parameters that specify the initial state of the qubits on the amount of their entanglement in the process of further evolution has been studied. It is shown that in the case of low intensities of the thermal field of the cavity, for one of the initial states of the qubits under consideration, the phenomenon of sudden death of entanglement is observed, while for the other initial state of the qubits such an phenomenon is absent. It has also been established that with an increase in the intensity of the thermal field, the sudden death of entanglement occurs for both states.