Study of atom-field interaction inside a cavity plays a major role in quantum optics. Quantities such as atomic inversion, entanglement dynamics and second order correlation, Mandel's Q parameters, Wigner distribution function are at the heart of quantum optics. In recent years, the entanglement has become ubiquitous in quantum technology. In quantum optical systems like ion traps, cavity quantum electrodynamics, quantum circuits, atoms and fields are used to study the entanglement dynamics.
In this work the tussling interplay between the thermal photons and the squeezed photons is discussed. Thermal and squeezed photons are chosen to represent the `classical' and `quantum' noises respectively, and, they are pitted against each other in a coherent background radiation field (represented by coherent photons). The squeezed coherent thermal states (SCTS) and their photon counting distributions (PCD) are employed for this purpose. It is observed that the addition of thermal photons and squeezed photons have counterbalancing effects, by delocalizing and localizing the PCD, respectively. Various aspects of the atom-field interaction, like the atomic inversion, and entanglement dynamics in the Jaynes-Cummings model have been investigated. Particular attention is given to the study of atomic inversion and entanglement dynamics due to the addition of thermal and squeezed photons to the coherent state. We have also studied the mixing of thermal photons and squeezed photons using coherent squeezed thermal states, for which the behaviour of PCD, atomic inversion, and entanglement dynamics are contrasting to those of squeezed coherent thermal states. The parameter ranges for these states for which the zero Hanbury Brown and Twiss correlation is exhibited are also obtained. The associated Wigner distribution functions are also discussed.
In another work, we investigate the entanglement dynamics between atom-atom, atom-field and field-field subsystems have been studied for the double Jaynes-Cummings model (DJCM). The squeezed coherent states (SCS) and Glauber-Lachs (GL) states are chosen for the radiation mode present within the cavities. For the atomic states, a maximally entangled Bell state is chosen to study the effects for a pure state and a Werner state to understand effects of mixedness. The atom-atom entanglement is measured using Wooter's concurrence, whereas the atom-field and field-field entanglements are studied using negativity. We also study the effects of interaction between the cavities by introducing Ising type interaction between the cavities. We also consider the effects of detuning in the system. Finally we study the effect of Kerr-nonlinearity on the entanglement dynamics. From these investigations we propose that through a proper choice of the interaction parameter, detuning parameter and Kerr-nonlinearity we can remove the entanglement sudden death from the dynamics.
We have also studied the mixed states version of the squeezed coherent states and the corresponding atomic inversion and entanglement dynamics for these states are investigated using Jaynes-Cummings model.