Speaker: Sanghyeok Park, Physics PhD Graduate Student
Abstract: In this talk, I delve into the physics of quantum bits (qubits) within semiconductor quantum dot devices and explore how their tunability enhances their potential for quantum computing applications. I will discuss two distinct projects centered on the tunability of Si/SiGe quantum dot devices: (i) single-shot latched readout of a quantum dot hybrid qubit (QDHQ) using barrier gate pulsing, and (ii) lowering and controlling qubit operation voltages using gate-biased illumination. In the first project, I will present single-shot measurements and demonstrate coherent Larmor oscillations of a QDHQ. I will detail several methods implemented to optimize a QDHQ for single-shot readout, a critical component for advanced quantum computing protocols. These methods include a barrier gate pulsing technique that dynamically controls quantum dot tunnel rates to facilitate the qubit latched readout process. In the second project, I will introduce a technique for adjusting the operating voltages of a quantum dot device. This approach leverages near infra-red light illumination in the presence of applied voltages to modify the trapped charges under the gates, enabling tuning of the trapped charges to change the operating points. By using this technique, sub-100 mV tuning across all gates in the (1,1,1) charge configuration for qubit operation of the triple quantum dot device is achieved. This work with Si/SiGe quantum dot devices provides a promising step towards the realization of scalable and tunable quantum processors.