关键词：量子比特 量子测量 双量子点 约化动力学
Abstract
This thesis is dedicated to the problem of quantum measurement of a solid-state qubit by a serially coupled double-dot detector. Two basic approaches in quantum transport and quantum measurement are first introduced, i.e. the Landauer-Büttiker scattering theory and the quantum master equation approach. By establishing the Hamiltonian of the measurement setup, the master equation for the reduced system is derived. This equation determines the time evolution of the state of the reduced system. The reduced state of the system is characterized by the reduced density matrix, which includes the diagonal elements describing the probabilities, and off-diagonal elements depicting the coherence of the quantum states. In this thesis, by employing the numerical simulation method, the time evolution of the quantum state is demonstrated, with the focus on the analysis of the dephasing mechanism. It is found that the dephasing rate is closely related to the tunnel coupling in the measurement device. As the tunnel coupling enhances (reduces), the corresponding decoherence would increase (decrease). Finally, the effect of energy renormalization on the measurement is briefly analyzed, and the measurement time and measurement efficiency are discussed.
