Electron Mediated Quantum Computing with Nuclear Spins

本研究旨在为基于相干控制固态自旋系统的量子计算新方法奠定基础。其关键特点是使用电子/核自旋系统，并各取其精华。核自旋是很好的量子比特，因为它们有很长的相干时间，但它们很难准备和读出。电子自旋可以在定义良好的计算状态下制备，并且已经证明了单个电子自旋读数。因此，新方法使用电子自旋来进行状态准备和读出，但核自旋是量子位。这些电子/核控制方法的发展将使新型固态量子信息处理器成为可能，并与量子点、自旋电子学和其他电子/核自旋方法相关，用于量子计算、通信、传感器和执行器。使这种方法可行的要素是通过各向异性超精细相互作用介导核/核相干自旋门。直接的偶极核/核自旋相互作用通常是缓慢的，一般为几kHz，然而电子/核自旋相互作用，超精细耦合，可以相当大，高达几100 MHz，这提供了电子和核自旋系统之间快速信息交换的手段。各向异性的超精细相互作用也使核/核门成为可能。在各向异性超精细相互作用的存在下，核自旋的量子化轴不是静态的：它根据电子自旋的状态而变化。因此，核自旋的控制空间要比电子或核自旋单独探索的空间丰富得多。本研究将发展这种电子/核控制方法的理论和实验证明。

This research aims to develop the foundations for a new approach to quantum computing based on coherently controlling a solid-state spin system. The key feature is to use an electron/nuclear spin system and to take the best from each. Nuclear spins make great qubits since they have long coherence times, but they are difficult to prepare and readout. Electron spins can be prepared in well-defined computational states and individual electron spin readout has been demonstrated. So, the new approach employs the electron spin for state preparation and readout, but the nuclear spins are the qubits. The development of these electron/nuclear control methods will be enabling of a new class of solid-state quantum information processors and have relevance to quantum dots, spintronics and other electron/nuclear spin approaches to quantum computation, communication, sensors and actuators.The element that makes this approach viable is the mediation of nuclear/nuclear coherent spin gates via the anisotropic hyperfine interaction. The direct dipolar nuclear/nuclear spin interactions are typically slow, generally a few kHz, however the electron/nuclear spin interaction, the hyperfine coupling, can be quite large, up to a few 100 MHz, and this provides a means of rapid information exchange between electron and nuclear spin systems. The anisotropic hyperfine interaction also enables nuclear/nuclear gates. In the presence of the anisotropic hyperfine interaction the quantization axis of the nuclear spin is not static: It changes depending on the state of the electron spin. The control space of the nuclear spin is thus far richer than has been explored for either electron or nuclear spins alone. This research will both develop the theory of such electron/nuclear control methods and experimentally demonstrate them.