Professor Wei-Min Zhan (Dept. of Physics, National Cheng Kung University)

Quantum Information Processing: A problem of open quantum systems

Abstract:
According to Richard Feynman, an open quantum system is defined as a principal quantum system of interest interacting with its environment of not interest. Study the effect of the environment on the subsequent dynamics of the principal system is a central issue in many currently interesting research topics related to quantum coherence phenomena, such as quantum decoherence in quantum computations and quantum information processes, quantum measurement theory and quantum transport phenomena, quantum dissipation dynamics as well as the foundation of quantum mechanics. These quantum phenomena of open systems are essentially associated with the quantum non-equilibrium dynamics, a subject that has been investigated over a half century and becomes more and more active in recent years due to the rapid development of nano-science and technology as well as the new emerging research field of quantum information science. In this talk, I will present a quantum decoherence theory we developed very recently for quantum dot system gated by electrodes. We utilize the coherent state path integral approach to reformulate Feynman-Vernon influence functional theory, which makes the influence functional theory applicable to arbitrary open quantum systems. The dynamics of electrons in quantum dot systems, in particular decoherence dynamics, is thus completely governed by a closed-time effective action which fully takes into account the back-reaction effects from its environments. The exact master equation is derived within this framework. I will also concentrate on the mechanism of intrinsic and/or extrinsic loss of quantum coherence of electrons in nanostructures.

2009 年 2 月 27 日
14:30~15:30

新數館 308 室