Quantum computing offers solutions to certain computational problems that are superior to classical solutions. Quantum computer prototypes based on electron or nuclear spins embedded in solids do exist by now, and the research community is trying to develop them further based on the vast knowledge and expertise of the semiconductor industry. The PhD student will join the spin-qubit theory research line of the PI, and will  work in strong collaboration with leading international experimental groups (e.g., TU Delft, Copenhagen, ISTA Austria) in the framework of the Horizon Europe projects "IGNITE" (Integrated Germanium Quantum Technology) and/or ONCHIPS (On-chip Integration of Electronics and Photonics). The main goal of the work is to facilitate experimental progress by providing a deep understanding of the physical mechanisms relevant for control, readout and decoherence of spin qubit in solids. Our work will also foster the scale-up of spin-qubit architectures: we will study gate and readout crosstalk effects in multi-qubit registers, advantages and disadvantages of shared-control schemes, and routes toward fault-tolerant quantum computing (quantum error correction).