Identifying and mitigating errors in hole spin qubit readout

High-fidelity readout of spin qubits in semiconductor quantum dots can be achieved by combining a radio-frequency (RF) charge sensor together with spin-to-charge conversion and Pauli spin blockade. However, reaching high readout fidelities in hole spin qubits remains elusive and is complicated by a combination of site-dependent spin anisotropies and short spin relaxation times. Here, we analyze the different error processes that arise during readout using a double-latched scheme in a germanium double quantum dot hole spin qubit system. We first investigate the spin-to-charge conversion process as a function of magnetic field orientation, and configure the system to adiabatically map the $\lvert \downarrow\downarrow \rangle$ state to the only non-blockaded state. We reveal a strong dependence of the spin relaxation rates on magnetic field strength and minimize this relaxation by operating at low fields. We further characterize and mitigate the error processes that arise during the double-latching process. By combining an RF charge sensor, a double-latching process, and optimized magnetic field parameters, we achieve a single-shot single-qubit state-preparation-and-measurement fidelity of 97.0%, the highest reported fidelity for hole spin qubits. Unlike prior works and vital to usability, we simultaneously maintain universal control of both spins. These findings lay the foundation for the reproducible achievement of high-fidelity readout in hole-based spin quantum processors.