Quantum Simulations for Quantum Technologies

Recent years have witnessed exponential growth in the development of quantum technologies for computation, sensing, and communication. Much of this progress stems not only from new experimental fabrication and characterization tools but also from a better and deeper theoretical understanding of hardware platforms. In particular, ab initio calculations can be used to predict materials' properties and even guide experimental realizations of more advanced quantum technologies. This dissertation explores the interplay between theory, first-principles calculations, and experiments for quantum technology applications, with a particular emphasis on solid-state spins. We address several questions: What makes solid-state spins better quantum sensors than their classical counterparts? How can we interpret the response of spin defects to environmental perturbations? From a complementary perspective, how can we harness the power of quantum computation to improve the prediction of properties of solid-state spins? By investigating these questions, this dissertation sheds light on connecting a rich variety of topics—including electronic structure theory, condensed matter physics, and quantum information science. More broadly, it showcases first-principle simulations as powerful frameworks for guiding our exploration of quantum physics.