ExpandQISE: Track 1: First- Principles Calculation of Quantum Defects via the Spin-Flip Bethe-Salpeter Equation Approach

Solid materials inevitably have defects such as missing atoms and impurities of a different kind of atom. These defects can have discrete energy levels like an individual atom, providing quantum states which can be used for applications in quantum computing, quantum sensing, and quantum communications. This project uses computational theory to understand the fundamental properties of such defects and identify promising candidates to be studied in the laboratory and considered for future technologies. The research team is developing a new methodology and applying it to a novel class of defects to assess their suitability. The methods developed are being implemented in open-source software, available for the research community at large, and made accessible via tutorials and workshops. The postdoctoral researchers and students are being trained in best practices for code development. The research benefits society and economic development by building the fundamental scientific knowledge for the advancement of quantum technologies. This project brings together faculty members from the University of California, Merced (UC Merced), Florida Polytechnic University, and the University of California, Santa Barbara (UC Santa Barbara) which has a well-established research program including the NSF-funded Quantum Foundry. The research team is adapting course modules from UC Santa Barbara on Materials for Quantum Information Science for classes at UC Merced and Florida Polytechnic and developing new hands-on web-based simulation tools and exercises about defects. Undergraduates at UC Merced and Florida Polytechnic will take part in the research. UC Merced students will join Quantum Foundry professional development activities, including student-led seminars and engagement with industry through industry internships and the annual Quantum Industry Showcase. An additional element is public outreach with the California Minerals and Mining Museum about how defects create colors in gemstones.

The continued development of quantum information science depends on identifying suitable qubits, single-photon emitters, and quantum memories. Point defects or impurities in semiconductors and insulators form an attractive platform for implementing these technologies. Theory can play an important role in identifying suitable new candidates for experimental investigation. However, accurate calculations of defect properties are quite challenging for standard electronic-structure methods. The research team's recently developed spin-flip Bethe-Salpeter equation approach to this problem has shown success on small molecules and on the NV and SiV0 centers in diamond. This project is further developing the spin-flip Bethe-Salpeter equation method, to make it more accurate and flexible. The method is then being applied to transition-metal impurities in wide-band-gap semiconductors or insulators, which are a primary target of interest in the field, in order to calculate optical spectra and radiative and non-radiative recombination. The research team brings together expertise specifically in the spin-flip Bethe-Salpeter method from junior investigators at UC Merced and Florida Polytechnic, with expertise in first-principles calculations of defects and recombination processes from a more senior investigator at UC Santa Barbara, to develop research and education in quantum information science at these two emerging institutions. This work advances the spin-flip Bethe-Salpeter methodology and code, providing a new tool for the quantum information science research community to use in first-principles studies of point defects, which overcomes the limitations of some existing methods. The research expands knowledge of particular defects in wide-gap semiconductors, helping in the search for new candidates for quantum technologies.