Crystalline Dielectrics For Improved Josephson Qubits

Superconducting quantum bits (qubits) are promising candidates for quantum computing in the solid state. Compared with other qubit implementations, they naturally provide strong coupling and are capable of scaling up by using standard microelectronics fabrication technology. However, one of the biggest challenges involved in building a high quality qubit is to eliminate the amount of noise that develops in the wiring of the superconducting circuit and defects in the Josephson junction---a key component of the qubit. In this thesis, I would describe our novel approach of probing the quality factor of low-loss single crystal silicon nanomembrane material, and the significant increase in the qubit energy relaxation times by incorporating it into our superconducting phase qubit circuit design. Then I would discuss our novel designs of superconducting through silicon vias which played an important role in eliminating radiation loss and decoherence. Finally, I report on our effort to test various potential low-loss dielectric materials for superconducting qubits, such as epitaxially grown low-loss dielectric materials.