Dephasing of planar Ge hole spin qubits due to 1/$\textit{f}$ charge noise

Abstract: Hole spin qubits in Ge, investigated for all-electrical spin manipulation because of its large spin-orbit coupling, are exposed to charge noise leading to decoherence. Here we construct a model of $1/f$ noise from individual fluctuators and determine the dephasing time $T_2^*$ as a function of qubit properties. $T_2^*$ decreases with increasing magnetic field and is an order of magnitude longer for out-of-plane than for in-plane fields for the same Zeeman energy. $T_2^*$ shows little variation as a function of the top gate field and is a complex function of the dot radius. Our results should help experiments to enhance coherence in hole qubit architectures.