Transport, Charge Sensing, and Quantum Control in Si/SiGe Double Quantum Dots*

Si/SiGe quantum dots hold great promise as ultra-coherent qubits [1]. In comparison with the GaAs system, Si has a weaker hyperfine interaction due to the zero nuclear spin of $^{28}$Si and smaller spin-orbit coupling due to its lighter atomic weight [2]. However, the fabrication of highly controllable Si/SiGe quantum dots is complicated by valley degeneracy, the larger effective electron mass, and the difficulty of obtaining high quality samples [3]. Here we develop a robust fabrication process for depletion mode Si/SiGe quantum dots, demonstrating high quality ohmic contacts and low-leakage Pd top gates. We report DC transport measurements as well as charge sensing in single and double quantum dots. The quantum dot gate electrode pattern allows a relatively high level of control over the confinement potential, tunneling rates, and electron occupation. \\[4pt] [1] C. B. Simmons \textit{et al.}, arXiv:1010.5828v1 (2010). \\[0pt] [2] R. Hanson \textit{et al.}, Rev. Mod. Phys. \textbf{79}, 1217 (2007). \\[0pt] [3] F. Sch\"affler, Semicond. Sci. Tech. \textbf{12}, 1515 (1997).