CAREER: Orbital-based Descriptors for Dynamical Properties of Quantum Defects

NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education to understand how quantum devices can be physically realized by defects in solids, as well as how to rank and optimize their performance in search of an ideal candidate. A quantum bit (qubit) – the fundamental unit in achieving quantum computation – requires a physical representation based on a quantum mechanical system with a binary degree of freedom to host its zeros and ones. Crystallographic point defects constitute one promising physical qubit platform. To qualify as an ideal defect-based qubit, a long list of performance requirements related to the defect’s physical properties need to be met. This project will focus on two such properties related to (i) how atomic vibrations affect light absorption, and (ii) how quickly defect spins can change states following light absorption. To model these properties, two sets of computer simulation methods will be developed. One set will perform accurate but computationally demanding calculations based on microscopic models, serving as reference for select defects. Another set of methods will rely on physically motivated approximations for higher computational efficiency; they will be calibrated and validated by the accurate methods and will streamline the evaluation of a wider variety of potential defect candidates. This project will benefit society and technological development by broadening the design space and delivering rational design rules for quantum devices.Integrated with research, the following educational activities will be developed. First, the PI will develop a workshop that guides high school students in reading research papers and formulating research questions in materials physics. The workshop will aim at guiding career aspirations in scientific, engineering, and mathematical disciplines and cultivating authentic research experiences in materials physics. Second, the project will develop a platform enabling high school students to generate virtual reality demonstrations of defect and crystal structures for outreach events at the Fort Worth Museum of Science and History. Third, the PI will introduce a new high performance computing module to the undergraduate computational physics curriculum at his institution. The project will also support travel to annual conferences at the Society for the Advancement of Chicanos/Hispanics and Native Americans in Science, where student experience and research outcomes will be shared with prospective Hispanic students interested in physics and inspire their careers in physics.TECHNICAL SUMMARYCrystallographic point defects constitute one promising physical platform for implementing spin-based qubits, delivering both potential scalability and long spin coherence times. As the search for ideal defect qubits advances, increasingly complex defect metrics need to be predicted and optimized. Despite recent advances in first-principles defect modeling, two dynamical properties of defects – electron-phonon coupling and intersystem crossing rates – remain hard to calculate and hard to interpret. To tackle this challenge, the PI and his team will develop orbital-based descriptors for Huang-Rhys factors (for electron-phonon coupling), excited-state spin-orbit coupling matrix elements, and singlet-triplet splitting, thereby delivering rational design rules to optimize them for qubit applications. The development of each descriptor will be accompanied by first-principles validation. Excited-state methods ranging from constrained density functional theory (DFT), time-dependent DFT, and the GW-Bethe Salpeter Equation approach will provide references, while ground-state DFT will be the basis of descriptor design. Established descriptors will be applied to a wider variety of defects and entered into a public database allowing user query, facilitating future modeling efforts.Integrated with research, the following educational activities will be developed. First, the PI will develop a workshop that guides high school students in reading research papers and formulating research questions in materials physics. The workshop will aim at guiding career aspirations in scientific, engineering, and mathematical disciplines and cultivating authentic research experiences in materials physics. Second, the project will develop a platform enabling high school students to generate virtual reality demonstrations of defect and crystal structures for outreach events at the Fort Worth Museum of Science and History. Third, the PI will introduce a new high performance computing module to the undergraduate computational physics curriculum at his institution. The project will also support travel to annual conferences at the Society for the Advancement of Chicanos/Hispanics and Native Americans in Science, where student experience and research outcomes will be shared with prospective Hispanic students interested in physics and inspire their careers in physics.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.