A Study of Dynamics of Open Quantum Systems: Quantum Statistical Mechanics, Functional Integral Approach, Quantum Optics

In this work the objective has been to investigate some aspects of the dynamics of quantum open systems, in particular the quantum theory of dissipation. This is a very vast and challenging topic ranging from fundamental aspects of quantum statistical mechanics, quantum optics to applications in as diverse areas as superconducting devices and quantum gravity. The approach used in these investigations is that of functional integration. This approach, apart from its beauty and elegance is also the most suitable one in the above scenario in that it is able to penetrate into regimes which are inaccessible by other means. The principal object used is the influence functional which is a functional integral that gives the effect of the environment on the system of interest. Here our main thrust has been to develop the tools and techniques of functional integration to investigate some aspects of quantum open systems in their generality. The quantum theory of a Stern-Gerlach system in contact with a linearly dissipative environment is investigated using the influence functional generalized to allow for nonfactorizable initial conditions. Then, the general problem of a two-level at