Development of hybrid atomistic/empirical modeling methods for donor-based quantum computing architectures
Silicon phosphorous donor based devices have emerged as promising candidates for future quantum computing devices. Despite the development of high precision fabrication techniques, inherent statistical variations of dopant placement on an atomic scale can influence device behavior in donor-based quantum computing systems considerably. Understanding the impact of statistical dopant placement variations on an atomic scale is thus of crucial importance for comprehensive device characterization. Existing atomistic based models such as tight-binding (TB) are to date unable to comprehensively model realistic statistical dopant placement variations in donor-based quantum computing systems due to immense computational requirements. The absence of feasible modeling methods therefore poses a significant challenge towards the goal of scalable donor-based quantum computing. Addressing the innovation imperative for novel atomic-scale methods capable of modeling realistic statistical dopant placement variations will close a major gap in current device characterization capabilities and provide important design guideline implications for future quantum computing devices. This work presents the development of novel hybrid modeling methods for single and multi-donor based quantum computing architectures. Firstly, a detailed study of the impact of lead dopant placement fluctuations in a single atom transistor is presented. Using a combined modeling approach of TB models and rate-equations, lead doping induced density of states fluctuations and their impact on the experimental charge stability diagram are investigated with atomic scale resolution. Secondly, a hybrid modeling methodology for multi-donor based quantum computing devices is presented. Based on atomistic TB simulations, empirical models and combinatorial algorithms, this new model served instrumental in the first demonstration of Pauli spin blockade in a multi-donor based device - a milestone in the development of donor-based quantum computing technology. In detail, the hybrid model determined the exact number of donors in the experimental device by rapid computation of statistically weighted binding energy spectra comprising millions of unique possible donor configurations. Practically unfeasible with any existing methods, the presented hybrid atomistic/empirical modeling methodology facilitates, for the first time, comprehensive characterization of statistical dopant placement variation effects in donor-based quantum computing architectures with atomic scale accuracy and unprecedented speed.
Klimeck, Purdue University.
Nuclear engineering|Quantum physics|Condensed matter physics
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