Identification and mitigation of errors in hole spin qubit readout

Abstract

High-fidelity readout of spin qubits in semiconductor quantum dots can be achieved by combining a radiofrequency charge sensor with spin-to-charge conversion and Pauli spin blockade. However, reaching high readout fidelities with hole spin qubits remains challenging due to site-dependent spin anisotropies and short relaxation times during readout. Here we analyse the multiple 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 $$\left\vert \downarrow \downarrow \right\rangle$$ ↓↓ state to the only non-blockaded state. We reveal a strong magnetic field strength dependence of the spin relaxation rates, and minimize it by operating at low fields. We further characterize and mitigate the error processes that arise during the double-latching process. By combining a radiofrequency charge sensor, a double-latching process and optimized magnetic field parameters, we achieve a single-shot, single-shot fidelity of 97.0% for single-qubit state preparation and measurement while maintaining control of both spins under the readout conditions.