Measurements to predict semiconductor qubit performance

Measurements with relatively fast turnaround times are sought to determine the end performance of quantum devices and circuits to assess new materials and speed the optimization of fabrication processes. While charge noise is considered by many to be the best assessment parameter short of full quantum operation, additional metrology is needed to provide information regarding fundamental mechanisms that degrade performance. By varying parameters such as temperature and magnetic field, charge transport measurements can characterize the basic properties of quantum materials and devices. Also, scattering mechanisms that cause dephasing and charge noise can be determined. By harnessing quantum effects such as weak-localization and Shubnikov – de Haas oscillations, we determined the effect of fabrication approaches on Si-based devices. For example, we have quantitatively characterized the spread of P-dopants in devices formed by using H-based scanning probe lithography, and we contrasted the properties of devices fabricated from isotopically purified Si with those fabricated on natural Si substrates. We are developing test structures, measurement methods, and analyses to extract parameters that can be correlated with key quantum metrics in Si devices to enable rapid, systematic feedback loops that link material growth and fabrication processes with qubit performance.