Electron Mediated Quantum Computing with Nuclear Spins

这项研究旨在为一种基于相干控制固态自旋系统的量子计算新方法奠定基础。关键特征是使用电子/核自旋系统，并从每个系统中取长补短。核自旋由于具有很长的相干时间而成为很好的量子比特，但它们很难准备和读出。可以在定义良好的计算状态下制备电子自旋，并且已经演示了单个电子自旋读出。因此，新的方法使用电子自旋进行状态准备和读出，但核自旋是量子比特。这些电子/核控制方法的发展将使一类新的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/核自旋方法在量子计算、通信、传感器和执行器中的应用有关。使这种方法可行的元素是通过各向异性超精细相互作用的核/核相干自旋门的中介。直接偶极核/核自旋相互作用通常很慢，一般为几千赫，然而电子/核自旋相互作用，即超精细耦合，可以相当大，高达几个100兆赫，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：它随电子自旋的状态而变化。到目前为止，核自旋的控制空间比单独探索电子或核自旋的空间要丰富得多。这项研究既将发展这种电子/核控制方法的理论，又将在实验上证明它们。

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.