Probing single electrons across 300 mm spin qubit wafers

Building a fault-tolerant quantum computer will require vast numbers of physical qubits. For qubit technologies based on solid state electronic devices, integrating millions of qubits in a single processor will require device fabrication to reach a scale comparable to that of the modern CMOS industry. Equally importantly, the scale of cryogenic device testing must keep pace to enable efficient device screening and to improve statistical metrics like qubit yield and process variation. Spin qubits have shown impressive control fidelities but have historically been challenged by yield and process variation. In this work, we present a testing process using a cryogenic 300 mm wafer prober to collect high-volume data on the performance of industry-manufactured spin qubit devices at 1.6 K. This testing method provides fast feedback to enable optimization of the CMOS-compatible fabrication process, leading to high yield and low process variation. Using this system, we automate measurements of the operating point of spin qubits and probe the transitions of single electrons across full wafers. We analyze the random variation in single-electron operating voltages and find that this fabrication process leads to low levels of disorder at the 300 mm scale. Together these results demonstrate the advances that can be achieved through the application of CMOS industry techniques to the fabrication and measurement of spin qubits.Comment: 15 pages, 4 figures, 7 extended data figure

Influence of Y and La Additions on Grain Growth and the Grain-Boundary Character Distribution of Alumina

Grain-boundary character distributions (GBCDs) were determined for spark plasma sintered Y- and La-doped aluminas prepared at temperatures between 1450 degrees C and 1600 degrees C. La doping leads to grain boundaries that adopt (0001) orientations 3.7 times more frequently than expected in a random distribution, whereas the Y-doped microstructures are more equiaxed. At 1500 degrees C, some of the boundaries in the Y-doped samples transform to a higher mobility complexion; in this microstructure, the {01 (1) over bar2} grain-boundary plane is 1.3 times more likely to occur than expected in a random distribution. After the fast-growing grains impinge, the dominant plane becomes {11 (2) over bar0} and these boundaries have areas that are 1.2 times more likely to occur than expected in a random distribution. The grain-boundary planes in the Y- and La-codoped samples preferred (0001) and {01 (1) over bar2>} orientations, combining the characteristics of the singly doped samples. Grain boundaries with a 60 degrees misorientation about [0001] were up to six times more common than random in the Y-doped samples. The preference for (0001) oriented grain-boundary planes in the La-doped sample persisted at all specific misorientations