Disentangling Orbital and Confinement Contributions to g-Factor in Ge/SiGe Hole Quantum Dots

Spin qubits are typically operated in the lowest orbital of a quantum dot to minimize interference from nearby states. In valence-band hole systems, strong spin-orbit coupling links spin and orbital degrees of freedom, strongly influencing the hole g-factor, a key parameter for qubit control. We investigate the out-of-plane g-factor in Ge quantum dots using excitation (single-particle) and addition (many-body) spectra. Excitation spectra allow us to distinguish the pure Zeeman g-factor from orbital contributions to the magnetic field splitting of states despite the strong spin-orbit coupling. This distinction clarifies discrepancies between g-factors extracted with the two methods, for different orbital states and different hole numbers. Furthermore, we find gate-tunability of g-factors at the level of 15%, highlighting its relevance for all-electric qubit manipulation.