Application of all-optical nuclear magnetic resonance to quantum computing

本研究的目的是阐明半导体量子结构中电子与核自旋相互作用的动力学，为以核自旋为量子比特的固态量子计算奠定基础。我们证明了在门控n-GaAs/A1 GaAs（110）量子阱中，可以通过改变背景电子密度来控制超精细相互作用和动态核极化.我们发现实验观察可以用金属-绝缘体转变来解释，超精细相互作用敏感地依赖于金属-绝缘体转变.利用时间分辨克尔旋转（TRKR）技术结合脉冲射频核磁共振技术，对半导体量子威尔斯中的核自旋相干性进行了探测。通过测量抽运脉冲和探测脉冲之间的固定时间延迟下克尔旋转的变化，观察了单脉冲共振射频磁场辐照后的时间核极化。我们跟踪拉比振荡作为射频脉冲宽度的函数。我们还采用了自旋回波技术来评估的内在的相干时间，这揭示了依赖于磁场相对于晶轴的取向，如预期的最近邻偶极-偶极相互作用。

The purpose of the research is to elucidate the dynamics of interaction between electron and nuclear spins in semiconductor quantum structures, and establish fundamental technology for solid state quantum computation in which nuclear spin is utilized as a qubit The achievements of the research are summarized as :1. We demonstrated that the hyperfine interaction and dynamic nuclear polarization can be controlled by changing the background electron density with gate electric field in a gated n-GaAs/A1GaAs (110) quantum well. We showed that the experimental observation can be explained by metal-insulator transition, on which the hyperfine interaction depends sensitively.2. We demonstrated detection nuclear spin coherence in semiconductor quantum wells by a time-resolved Kerr rotation (TRKR) technique combined with manipulation by pulse rf NMR. The temporal nuclear polarization after the irradiation of a single-pulsed resonant rf magnetic field was observed by measuring the change of the Kerr rotation at a fixed time delay between pump and probe pulses. We traced the Rabi oscillation as a function of the rf pulse width. We also employed a spin-echo technique to evaluate the intrinsic coherence time, which reveals the dependence on the orientation of the magnetic field with respect to the crystalline axis as expected by the nearest neighbor dipole-dipole interaction.