Special Physics Seminar

Electron Spin Qubits in Si/SiGe Quantum Dots

Mark A. Eriksson

Department of Physics
University of Wisconsin-Madison

It is intriguing that silicon, the central material of modern classical electronics, also has properties well suited to quantum electronics. Recent advances in silicon/silicon-germanium (Si/SiGe) materials have enabled the creation of high-quality gate-defined quantum dots in Si/SiGe heterostructures. Such gated quantum dots, also known as artificial atoms, enable the confinement of individual electrons. Motivated in part by the potential for very long electron spin coherence times in silicon, we are pursuing the development of electron spin qubits in Si/SiGe quantum dots. I will discuss our recent demonstration of single-shot spin measurement in such a qubit, and the measurement of spin-relaxation times longer than one second in such a system. These and similar measurements depend on a knowledge of tunnel rates between quantum dots and nearby reservoirs, or between pairs of quantum dots. I will discuss the measurement of these tunnel rates, the loading of specific quantum states by the control and tuning of those rates, and the use of tunnel rate measurements to perform spectroscopy of the quantum dot energy levels, both spin and orbital. Finally, I will discuss the potential for future advances in Si/SiGe materials, including the use of SiGe/Si/SiGe nanomembranes to aid in the growth and fabrication of very low disorder heterostructures and quantum dots.