Masters Defense: Anders Kringhøj

Readout and Control of Semiconductor Nanowire Based Superconducting Qubits

Superconducting quantum bits (qubits) are promising candidates for scalable, fault-tolerant quantum computation. Being able to determine a quantum state with a single measurement is essential for using any quantum system for computation. In this thesis single shot readout is implemented for hybrid semiconductor based superconducting qubits by integrating a near quantum limited parametric amplier in the existing cryogenic setup. We achieve a readout fidelity of around 70%, limited by the  1-2 μs lifetimes. However prolonging qubit coherence in future experiments will potentially allow the readout fidelity to reach the state of the art. Combining the single shot readout with two-qubit operations the rst steps towards entanglement demonstration are taken. Further experiments implementing feedback to correct drift in qubit frequency along with an extensive study of qubit anharmonicity are performed to investigate the physics of the qubit.