Estelle defended her PhD thesis entitled “Radiofrequency readout of hole spins confined in semiconductor quantum dots”,On November 8th.
Holes in the valence band of group-IV semiconductors benefits from natural spin-orbit interaction. Consequently, holes spins can be manipulated with electric field offering perspectives for quantum information processing. Among the different semiconducting materials, Silicon and Germanium stand out for the fabrication of quantum dot devices. On one hand, isotopically purified Silicon offers a clean magnetic environment together with very mature fabrication process. On the other hand, Germanium shows high mobilities and low effective masses in Ge/SiGe quantum well heterostructures, offering a large freedom in device design. In this manuscript, we explore
the spin physics of holes confined in semiconductor quantum dots focusing on readout techniques allowing for spin states detection. We first explore the dispersive readout of holes in Silicon-on-Insulator nanowires. For these purpose, we design and fabricate Nobium Nitride superconducting microwave resonator, and implement a gate-reflectometry setup working at a few gigahertz. Second, we focus on the charge sensing of double quantum dots (DQDs) in Ge/SiGe heterostructures. We implement a radiofrequency setup on a charge sensor made of a single quantum dot allowing for the assessement of the DQD charge states in less than
a microsecond. Associated with a measured charge noise around 0.2μeV/√Hz, this setup allows to reach the last hole regime of the DQD. Eventually we demonstrate the detection of Pauli Spin Blockade. Using this spin-to-charge conversion mechanism, we access the spin states of the DQD and report on their energy relaxation rates.