Dephasing of planar Ge hole spin qubits due to 1/f charge noise

Hole spin qubits in Ge, investigated for all-electrical spin manipulation because of their large spin-orbit coupling, are exposed to charge noise, leading to decoherence. Here, we employ a model of 1/f noise due to individual fluctuators and determine the dephasing time T2∗ as a function of qubit properties. T2∗ decreases with increasing magnetic field and is an order of magnitude longer for out-of-plane fields than for in-plane fields for the same Zeeman energy. T2∗ 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 enhance coherence in hole qubit architectures.