具自旋軌道交互作用雙端量子環之自旋傳輸特性

Abstract

本論文主旨是在探討介觀環在自旋軌道交互作用影響下對於自旋傳輸的影響，當電子自旋入射進兩端導線連接的介觀環時，在環中可以透過調整自旋軌道作用的強度來改變電子得到的AC相位進而影響其自旋傳輸結果，因此可以藉由改變參數來對入射電子的自旋產生不同方向的翻轉，也就是量子閘的作用。在本文中將會推導出介觀環之散射矩陣，透過分析介觀環之反射率挑選適當的參數便可以得到無損耗的量子閘。

The spin transport of mesoscopic rings with spin orbit interation under electric fields are studied. When an electron goes through a mesoscopic ring connected with two external leads, AC phase gained by the electron can be changed by varying the strength of spin orbit interaction via an external electric field, hence the influence on spin-dependent electron transport. For this reason, the incoming spin can be rotated to different position on Bloch sphere by varing the parameters in this system, which corresponds to the function of a quantum gate. After deriving the scattering matrix of a mesocopic ring, the reflection coefficient of the ring can be obtained. A lossless quantum gate can be built by choosing appropriate parameters. It is shown that all the important single qubit quantum gates which are loseless can be built by coupling loseless rings together.