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Quantum computers (QC), if realized, could disrupt many computationally intense fields of science. The building block element of a QC is a quantum bit (qubit). Qubits enable the use of quantum superposition and multi-state entanglement in QC calculations, allowing a QC to simultaneously perform millions of computations at once. However, quantum states stored in a qubit degrade with decreased quality factors and interactions with the environment. One technical solution to improve qubit lifetimes and network interactions is a circuit comprised of a Josephson junction-based qubit located inside of a high Q-factor superconducting 3D cavity.It is known that niobium resonators can reach $Q_{0}>10^{11}$Q0>1011. However, existing cavity geometries are optimized for particle acceleration rather than hosting qubits. RadiaBeam Technologies, in collaboration with Argonne National Laboratory and The University of Chicago, has developed a niobium superconducting radio frequency quarter-wave resonant cavity (QWR) for quantum computation. A 6 GHz QWR was optimized to include tapering of the inner and outer conductors, a toroidal shape for the resonator shorting plane, and an inner conductor tip to reduce parasitic capacitance. In this paper, we present the results of the resonator design optimization, fabrication, processing, and testing.

In French, the local mixed enterprise corporation (SEML) have been involved in the regional development for 50 years but paradoxically most of the research about them deals with their legal nature. This thesis places the SEML into the crossed control work between the State, the Local Authorities and the Deposit and Consignment Office. First the State privileged tool, they have gradually taken refuge in the Local Authorities, together with the diversification of their fields of intervention. Thus they testify to the power stakes between decentralization and recentralization, free enterprise and social and economic control. Locally, governing methods and urban cultures have an influence on their role and their positioning, as attested by the analysis of the towns of Bordeaux, Rennes and Montpellier. The European influences feed the prospective debate with different experiences on urban planning, land ownership and the respective role of public and private participants, the SEML being part of both the movement of the European Local Public Enterprises and the Public Private Partnerships. Thus the contribution of this thesis lies in the approach of urban and territorial policies under the scrutiny of one of the operational participants in their implementation, being both a participant and a witness., En France, les Sociétés d'Economie Mixte Locales (SEML) participent depuis 50 ans à l'aménagement du territoire mais paradoxalement la plupart des recherches les concernant traitent de leur nature juridique. Cette thèse resitue les SEML dans les jeux de régulations croisées entre l'Etat, les Collectivités Locales et la Caisse des Dépôts et Consignations. D'outil privilégié de l'Etat elles sont passées progressivement sous l'égide des collectivités locales, accompagnant la diversification des champs d'intervention de celles-ci. Elles sont ainsi témoin des enjeux de pouvoir entre décentralisation et recentralisation, libéralisme et régulation économique et sociale. Localement, les modes de gouvernance et les cultures urbaines influent sur leur rôle et leur positionnement tel qu'en témoigne l'analyse des agglomérations de Bordeaux, Rennes et Montpellier. Les influences européennes alimentent le débat prospectif avec des expériences différentes de la planification urbaine, de la propriété foncière et du rôle respectif des acteurs publics et privés, les SEML s'inscrivant tout à la fois dans le mouvement des Entreprises Publiques Locales européennes et des Partenariats Public Privé. L'apport de cette thèse réside ainsi dans l'approche des politiques urbaines et territoriales avec le regard d'un des acteurs opérationnels de la mise en œuvre de celles-ci, tout à la fois acteur et témoin.