Research On The Decoherence And Quantum Optical Effects Of Superconducting Qubits

Superconducting quantum computation is one of the most promising methods to implement quantum computations. Superconducting qubit is the core unit of superconducting quantum computer, and one computer will be formed by thousands of qubits. The coherence time of three-dimensional(3D) Transmon qubit is the longest one among kinds of proposed qubits. Because of the simple fabrication processs and better decoherence times, so more and more groups in the world are focusing on 3D Transmon qubit. This thesis is research on the 3D Transmon qubit from the aspect of simulation, fabrication and measurement. Moreover, decoherence times and some quantum optics effect are also studied. In the end, several applications based on phase-slip junctions are proposed.In this thesis, the aluminum based 3D resonator which used to place the qubit is firstly investigatived. The commercial microwave software HFSS(High Frequency Structure Simulator) is used to simulate the 3D resonators. The relationship between the loaded quality factor and the distances from the microwave connector to the cavity is mainly studied. Both the simulation and measurement results can be fitted well by exponential equations. The sample fabrication processes are performed by two angle evaporation technique on silicon oxide chips. In the spectrum measurement, we observed photon number splitting based on 0 1 transitions, and photon number splitting based on 0 2 two photon transitions. In the time domain measurement, rabi oscillation, energy relaxation, ramsey fringe and spin echo are used to characterize the decoherence times of the 3D Transmon qubit. Also, according to this platform, we studied resonant and non-resonant Aulter-Townes Splitting effect, and the results can be fitted well by theoretical equations.Besides, we proposed an energy band tunable phase-slip flux qubit based on series phase-slip structures, further, when series a large inductance into the qubit loop, a tunable and flux noise insensitive phase-slip flux qubit can be get. In this thesis, the series phase-slip structures are also used to substitute the input and output capacitors of the Coplanar Wavegudie Resonator(CPW resonator), then, a loaded quality factor tunable CPW resonator can be get. In other words, we realized a photon switch in the microwave domain, which can provide a new aspect for cavity quantum electrodynamics research.In this thesis, the features of 3D Transmon are thoroughly studied from the view of simulation, fabrication and measurement, the decoherence features are also characterized in detail. Additionally, the photon number splitting and Aulter-Townes Splitting effect are studied, and several applications based on phase-slip junctions are proposed, which supported the theoretical and experimental research on cavity quantum electrodynamics, quantum optics and qubit scalabale on chips in the future.