Browsing by Author "ISKANDAR BIN BAHARI,Assistant Professor"

In this research, I aim to construct a scientific model to describe atom-field interaction under the influence of temperature by using one of the approaches of quantum field theory namely thermo field dynamics. This is because, the dynamics of many-body quantum system in thermal environment is not well understood and the comparison of physical properties such as purity and entanglement with the Jaynes-Cummings model has never been discussed before. I solved the energy eigenvalue problem of the system of interest to obtain the energy spectrum and the analogous stationary states relative to the ordinary Jaynes-Cummings model. I assumed the initial state of the atom and the field to be the pure state of two-level atom and the chaotic state (for case I interaction) or number-chaotic state (for case II interaction) respectively. By applying time evolution operator, I computed the steady state of the system. I plotted the Bloch vector magnitude and von Neumann entropy to examine the purity and entanglement behaviours of the system as time evolves. The subsequent chapter was dedicated to the physical interpretation of case I and case II interactions. I demonstrated that the collapses and revivals of Rabi oscillations of my models are non-periodic and have non- diminishing fluctuations of amplitudes which are in opposition to the ordinary Jaynes- Cummings model. Case I interaction only revives its purity and disentanglement incompletely for a single instance whereas case II interaction only revives its purity and disentanglement for two times. I also found that at longer times, the atom tends to evolve to always be highly mixed and highly entangled with the field state. The frequency of Rabi oscillations is also higher than the ordinary Jaynes-Cummings model due to the presence of thermal operators in the generalized Rabi frequency. I predicted that should I consider higher-order number-chaotic state, the number of collapses and revivals of Rabi oscillations may occur more frequently.