In this thesis, we focus on consummating current quantum dissipation theories and developing innovative non-perturbative protocol, to meet physically increasing demands for investigating modern complex open systems and emerging phenomena. As previous exact approaches, the path integral based methods have many advantages over perturbative quantum master equations, including physically reliable results and numerical stability. Meanwhile, it has shortcomings such as the expensive numerical cost, assumption on bosonic dissipation environment and is limited to reduced system evaluation. As a consummation of previous path integral theories, we successfully reduce the numerical consumption by modifying the existing formalism. On the other hand, we propose a novel non-perturbative theo...[ Read more ]

In this thesis, we focus on consummating current quantum dissipation theories and developing innovative non-perturbative protocol, to meet physically increasing demands for investigating modern complex open systems and emerging phenomena. As previous exact approaches, the path integral based methods have many advantages over perturbative quantum master equations, including physically reliable results and numerical stability. Meanwhile, it has shortcomings such as the expensive numerical cost, assumption on bosonic dissipation environment and is limited to reduced system evaluation. As a consummation of previous path integral theories, we successfully reduce the numerical consumption by modifying the existing formalism. On the other hand, we propose a novel non-perturbative theory, based on a quasi-particle description of dissipative environment. It remarkably goes beyond the path integral based methods, capable of studying strongly correlated system-and-bath dynamics, and applicable to not only conventional boson bath, but also physically appealing exciton or spin bath in studying novel nano-materials.