Preliminary Exam

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Investigation of oxide defects and heterostructure modifications for use in quantum computing
Date: Wednesday, December 13th
Time: 3:30 pm - 5:30 pm
Place: B343 Sterling
Speaker: Emily Joseph, Physics PhD Graduate Student
Abstract: Si/SiGe quantum dots are attractive candidates for quantum computation yet there are significant challenges to overcome in an effort to improve the scalability of the system. These devices are susceptible to charge noise, some of which may arise from two-level systems (TLS) in the oxide. In this work we use resonator measurement and STEM images to investigate ALD oxide quality to improve semiconducting qubits. Another challenge inherent to Si/SiGe quantum dots is the energy splitting of the conduction band valley states. The valley splitting in Si devices is largely variable and unpredictable and it would be advantageous to be able to predictably rely on a designed-in valley splitting. A modification to the heterostructure has been produced with oscillating concentration of Ge through the quantum well, called the Wiggle Well. Theory predicts that this structure will show strong spin-orbit coupling and with shear strain can have a deterministically large valley splitting. Here we describe methods for mechanically introducing shear strain into the quantum well and a proposed experiment measuring the spin-orbit coupling of the Wiggle Well and making a Loss-DiVincenzo qubit without a micromagnet.
Host: Mark Eriksson
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