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The presentation will be in English.
In a world transitioning to the era of second quantum revolution, avoiding processes such as dissipation, which annihilates the quantum state unnecessarily, is crucial. Therefore, understanding the sources of loss responsible for the relaxation in a given quantum system is highly relevant. Since superconducting quantum circuits are the favorite contenders for quantum computing, two directions are followed in this work to study the sources of loss in such circuits.
1. Superconducting high quality factor resonators have several applications in quantum technology. They are also the best test beds to study losses. In this work, the study of losses is carried out by realizing Aluminum resonators of different mean free path and capacitances. The behavior of the internal quality factor as a function of applied microwave power and temperature is investigated. The study focuses on the quasiparticle and dielectric losses in the resonators which have been argued to be the main cause of losses in superconducting quantum circuits. A comparative analysis of ground plane loss is also carried out in order to estimate the losses caused by the metallic ground plane.
2. Fluxonium qubit is one of the state of the art superconducting qubits. Their relaxation times are as high as 8-10 milliseconds in 3D architecture. To achieve large scalability, the qubits must be fabricated using 2D architecture. The change in architecture places new constraints on traditional sources of loss while also introducing new ones. The sources of loss causing qubit relaxation in 2D Fluxonium qubit are the area of emphasis in this work. Furthermore, the causes of noise in such a qubit are examined in order to understand the limitations on the coherence of the qubit.
The committee members are:
Dr. Marco Aprili, Laboratoire de physique des solides d’Orsay, Reporter
Dr. Ioan Mihai Pop, KIT, Reporter
Prof. David B. Haviland, KTH, Examiner
Dr. Florence Levy-Bertrand CNRS, Examiner
Prof. Laurent Saminadayar, Université Grenoble Alpes, Examiner
