Conventional electronics focuses on the manipulation of electric charge to transfer and process information. Instead of encoding information in the presence or absence of electrons, one can exploit their quantum states. Since flipping quantum states requires only a fraction of the time and energy needed to change local charge by moving electrons, these approaches promise much higher clock speeds and lower power consumption than conventional electronics. Furthermore, using quantum states allows for exploiting quantum correlation effects: quantum computing may solve complex problems like factorization in the fraction of the time of a classical computer. Novel two-dimensional crystals such as graphene are ideal materials for spintronics and valleytronics due to their exceptional tunability, unique bandstructure and large spin and valley coherence times. It is now possible to confine electrons in graphene and directly measure the individual spin and valley states, realising edge-free quantum dots. Despite these advances, there are many challenges and questions remaining to fully realize the potential of spin- or valleytronic devices: How can we coherently manipulate individual spins? What are the relevant time and energy scales to observe and exploit the resulting dynamics? How do the properties of ideal graphene map to realistic devices with disorder, charge impurities and finite size effects? This project aims to simulate electron scattering at spin impurities in graphene in close collaboration with the experiment as well as to couple single vacancy defects to edge-free graphene quantum dots.