Collaborative Research: Physics and Quantum Technology Applications of Defects in Silicon Carbide

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NONTECHNICAL SUMMARYThis award supports theoretical and computational research on defects in materials that are good candidates to be used for quantum computing. Silicon carbide is a promising material for quantum information processing due to its maturity in industry and compatibility with current electronic device fabrication. Defects refer to disruptions in the perfect regular array of silicon and carbon atoms in a perfect silicon carbide crystal. Promising defects include vacancies such as a silicon atom missing from a site where it is expected or a missing silicon and missing carbon atom on neighboring sites; and the presence of a nitrogen atom along with an associated vacant site. Electrons are confined to quantum mechanical states localized in a small volume. These states can be initialized, manipulated, and measured; they are promising candidates for qubits which are the quantum computer analogs of bits in ordinary computers. Defects in silicon carbide have attractive properties for a range of applications, including quantum-enhanced sensing of electric and magnetic fields, secure quantum communications over long distances, as well as quantum computation. The PIs will develop theoretical tools to understand and exploit the most promising defects in silicon carbide and assess their potential for applications. In particular, the PIs will calculate the dynamics of these defects under interaction with lasers and with static electric fields, using both computational techniques and analytical theory. This work will pave the way toward sensing applications. The properties of the emitted light will also be studied, which will lead to the design of new light-matter interfaces for long-range quantum communication networks. The interactions between the defects and their environment, including the nuclear and vibrational modes, will be calculated, and their effect on the performance of the defect will be assessed. The PIs will also investigate new ways of controlling these quantum systems. The outcomes of this research will contribute toward the development of silicon carbide based systems for powerful future quantum information technologies. This project will also contribute to educating and supporting the next generation of researchers in quantum information science and technology. Technical summaryThis award supports theoretical and computational research and education to use first principles techniques to investigate the physics and dynamics of defects in silicon carbide, including the process of spin polarization through intersystem crossing and the coupling to electric fields for sensing and spin control applications. A formalism for dynamic nuclear polarization calculations will be developed to understand existing experiments and to reveal the distinct physics of a central spin coupled to two distinct nuclear baths. The viability of silicon carbide devices for quantum communications and repeaters will be assessed. Specifically, this project will characterize spin-photon interfaces for quantum information applications by taking into account mixings of states and couplings to vibrational modes obtained from first principles calculations. Spin control techniques beyond those for qubits will be developed to exploit the silicon vacancy center with S=3/2. The theoretical results of this project will be compared to experimental data and stimulate further experimental studies. This project will also contribute to educating and supporting the next generation of researchers in quantum information science and technology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.