Application of all-optical nuclear magnetic resonance to quantum computing

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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.