Stark tuning of electronic properties of impurities for quantum computing applications
Abstract
Understanding the behavior of donor bound electronic states under electric and magnetic fields is a fundamental issue critical both to the development of novel quantum technologies and to the on-going miniaturization of semiconductor devices. Single donor systems in silicon have already been proposed as the building blocks of a potentially scalable quantum computer that draws upon the vast experience of the semiconductor industry and takes advantage of long spin coherence times. We employed an atomistic tight-binding technique with several million atoms to to provide the most precise and comprehensive investigation of quantum control of donor electrons in semiconductors. We investigate the electric field response of donor hyperfine constants and effective g-factors, resolving past discrepancies between experiments and theory, and in the process, characterizing some single spin control parameters for a donor qubit. Our Stark effect simulations involving a single donor near a semiconductor-insulator interface demonstrates the gate induced adiabatic ionization and dimensional symmetry transition of the donor electron from a 3D atomic Coulomb well to a 2DEG-type system, and was able to explain recent transport spectroscopy measurements on single donors. The ability to induce such symmetry transitions is a critical functionality requirement in donor qubits. We also investigate gate controlled single electron localization in multiple donor wells in order to explore charge qubit design issues and to verify a coherent electron tunneling mechanism across a donor chain. Finally, two-electron states of donor molecules in the presence of electric fields are computed using many-body methods in order to study exchange energy, a quantity of interest for two-qubit operations.
Degree
Ph.D.
Advisors
Hollenberg, Purdue University.
Subject Area
Electrical engineering|Condensed matter physics|Materials science
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