Nonclassical properties and purity of a qubit system in photon-added squeezed thermal states with time-dependent coupling effect

• Two-level system interacting with photon-added squeezed thermal field.
• Effect of the squeezed parameter and photon-added number.
• Dynamical evolution of the linear entropy and Mandel's parameter.
• Optimal condition for maximal value of the physical quantifiers.
• Asymptotic limit behavior of the linear entropy and Mandel's parameter.

The degree of purity and nonclassical properties for a two-level system interacting with a photon-added squeezed thermal field (PASTF) are described in terms of the physical parameters involved in the whole system state with and without time-dependent coupling effect. Specially, we investigate the influence of the squeezed parameter and photon-added number on the behavior of the linear entropy and the Mandel's parameter. We find that for each value of the photon-added number, there exist critical value of the squeezed parameter for which the linear entropy is maximal and the statistical properties get farther from the trivial case. Moreover, we show that the presence of the time-dependent coupling effect may increase the periodicity time and lead to quench oscillations of the Mandel's parameter during the evolution. Finally, we exploit an interesting relationship between the linear entropy and the Mandel's parameter in terms of the physical parameters.