Developing Metrics to Identify Relevant Defects in Quantum Devices using First-Principles Calculations

Active defects in silicon-based qubit devices are thought to be a large driver of charge noise. A challenge in studying these devices is the large number of defects that could occur. However, some point-defects like vacancies may have electronic structures that are similar which experimental techniques cannot distinguish between. In addition, not all defects will significantly impact device performance due to their electric properties being such that they do not cause much charge noise. In this work, we use density functional theory to systematically characterize features of interfacial defects to develop metrics to determine what defects would be of interest both experimentally and computationally. We analyze the local density of states and formation energies of point vacancies at silicon-silica interfaces. Preliminary results indicate that vacancy defects most likely form near the interface and do not have similar electronic structures whereas vacancies past 15 Angstroms from the interface are more likely to be similar but are unlikely to form. These results motivate investigation into how other characteristics of defect trap states such as energetics can be used to down select defects of interest. 

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