球型量子点量子比特的声子退相干效应

采用求解能量本征方程、幺正变换及变分相结合的方法，研究声子效应对球型量子点中电子-声子系（极化子）能量、量子比特性质的影响。数值计算表明，能量随量子点尺寸的增大而减小，说明量子点具有明显的量子尺寸效应；当考虑声子效应时，能量、量子比特的振荡周期均减小，说明声子效应使得量子比特的相干性减弱；且量子比特内各空间点的概率密度均随时间做周期性振荡，不同空间点的概率密度随径向坐标和角坐标的变化而变化。

The Decoherence Effect of Phonon in Qubit in Spherical Quantum Dot

The influence of phonon effect on the energy of polaron and the properties of a quantum bit in spherical quantum dot were studied by solving precisely the eigen-energy equation ,LLP unitary transformation and variation method . The numerical results showed that the eigen-energy of the electron or polaron in spherical quantum dot decreased with increasing quantum dot radius and the quantum size effect was obvious. When the effect of phonon was taken into account, the eigen energy of the ground state and the first excited state were lowered, leading to oscillating period of quantum bit shorting and coherence of quantum bit weakening. The numerical results also indicated that the probability density distribution of electron or polaron in different space point in qubit was different and all did periodicity oscillating with same time period.