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.
