QDev Masters Defense: Laurits Andersen

Superconducting Qubits Based on Semiconductor Two Dimensional Electron Gases and Selective Area Grown Nanowires
Superconducting qubits based on voltage tuneable superconductor-semiconductor Josephson junctions called gatemons could be used to realize a universal quantum computer. Before this can be realized, two challenges must be overcome; the coherence times of the qubits must be longer, and fabrication must be deterministic. This thesis presents the nanofabrication and characterization of two gatemon qubit devices based on different materials. In one the Josephson junction is based on a proximitized two dimensional electron gas. The other device is based on nanowires grown directly on the substrate using selective area growth. The lifetimes and coherence times for these devices are extracted, finding T1 = 2.77 μs and T2* = 359 ns for the first device and T1 = 180 ns for the second device with the coherence time being too short to measure.