Dynamics of open quantum systems

Seminar Quantum Dynamics
on Wednesday, August 8th, 2007

Rupamanjari Ghosh
Jawaharlal Nehru University, New Delhi

Dynamics of open quantum systems

No system of interest, except the entire universe, can be thought of as an isolated system - the system is in fact 'open', each surrounded by its environment. We use the path-integral formalism of quantum mechanics to first handle the problem of quantum Brownian motion, generalized to nonlinear system-environment couplings and nonfactorizable initial conditions. We then review some of our models of open quantum systems which shed light on the problem of quantum-to-classical transitions via decoherence, because of the interaction of the quantum system with an external environment. We also examine the open quantum system of a two-level atom, or equivalently, a spin-half system, in interaction with quantum reservoirs of either oscillators or spins, under the quantum nondemolition condition of the Hamiltonian of the system commuting with the system-reservoir interaction - a topic relevant for ongoing experimental efforts in quantum information.