QARPET: A Crossbar Chip for Benchmarking Semiconductor Spin Qubits

Large-scale integration of semiconductor spin qubits into quantum processors hinges on the ability to characterize quantum components at scale, a task challenged by their operation at sub-kelvin temperatures, in the presence of magnetic fields, and by the use of radio-frequency signals. Here, we present QARPET (Qubit-Array Research Platform for Engineering and Testing), a scalable architecture for characterizing spin qubits using a quantum dot crossbar array. The crossbar features tightly-pitched spin qubit tiles and is implemented in planar germanium, by fabricating a large device with the potential to host 1058 hole spin qubits. Measurements on a patch of 40 tiles demonstrate key device functionality at millikelvin temperatures, including tile addressability, threshold voltage and charge noise statistics, and the characterisation of hole spin qubits and their coherence times in a single tile. These demonstrations pave the way for a new generation of quantum devices designed for the statistical characterisation of spin qubits.