Quantum gates by coupled asymmetric quantum dots and controlled-NOT-gate operation

A quantum computer based on an asymmetric coupled-dot system has been proposed and shown to operate as a controlled-Nor gate. The basic ideas an the following. (1) The electron is localized in one of the asymmetric coupled dots. (2) The electron transfer takes place from one dot to the other when the energy levels of the coupled dots are set to be close. (3) The Coulomb interaction between the coupled dots mutually affects the energy levels of the other coupled dots. The decoherence time of the quantum computation and the measurement time are estimated. The proposed system can be realized by developing the technology of the single-electron memory using Si nanocrystals, and a direct combination of the quantum circuit and the conventional circuit is possible.