Silicon/silicon-germanium quantum dots with single-electron transistor charge sensors.

摘要

Si/SiGe quantum dots (QDs) are promising candidates for spin-based quantum bits (qubits) as a result of the reduced spin-orbit coupling as well as the Si isotopes with zero nuclear spin. Meanwhile, qubit readout is a challenge related to semiconductorbased quantum computation. A superconducting single-electron transistor (SET), when operating in the radio-frequency (rf) regime, has a combination of high charge sensitivity and low back-action and can potentially become an ideal charge sensor for the QDs.;This thesis describes the development of superconducting SET charge sensors for Si/SiGe QDs. Using rf-SETs we have detected real-time electron tunneling events on the order of 10 microseconds in a single QD and mapped out the stability diagram of a double QD, showing spin blockade and bias triangles due to excited-state transitions. In Addition, Kondo effects that are significantly different from the standard spin 1/2 model have been observed and investigated in both perpendicular and in-plane magnetic fields, indicating the interplay between the spin and valley degrees of freedom in Si.