Fabrication Of Quantum Bit Devices

Superconducting quantum computing is a solid-state technology scheme of quantum computing.Superconducting quantum bit is its basic unit.Superconducting qubits have the characteristics of easy integration,low loss,and control of circuit parameters through physical structure.Superconducting quantum computing have been a hot topic at home and abroad Since its introduction.However,there are many breakthroughs in superconducting qubit circuits.On the one hand,superconducting qubits are easily coupled with the surrounding electromagnetic environment,thereby shortening the time from the excited state to the ground state,that is,the decoherence time is shorter.On the other hand,with the deepening of research on superconducting qubits,the current superconducting quantum bit integration scale has evolved from two or three qubits to more than a dozen qubit couplings,key issues such as coupling,integration,and packaging between multiple qubits are becoming increasingly apparent.In this paper,3D-transmon is used as a model,combined with experimental measurement system,the structure of 3D-transmon is designed.The preparation process of Josephson junction of Al/AlOx/Al structure is studied.3D-transmon is successfully prepared.The sample has a decoherence time T1 of about 566 ns.The reason for the short decoherence time T1 is analyzed,and the post-sample preparation process is improved according to the analysis results.At the same time,the superconducting multi-qubit integration and packaging process are preliminary.Exploring,using low melting point tin as electrode material,the preparation process of the electrode on gold substrate was preliminarily studied.The specific work is as follows:1.Analysis and design of 3D-transmonA variety of superconducting qubits are introduced,and the influence of physical parameters in the 3D-transmon structure on the circuit is analyzed.Combined with the experimental measurement system,3D-transmon was designed.2.3D-transmon preparation and measurementElectron beam lithography was used to prepare a submicron double-layer adhesive suspended mask on a high-resistance Si substrate,which focused on solving the problem of electron beam exposure dose and underlayer development time,and then evaporating electron beam obliquely and vertically evaporating.Combining to prepare an Al/AlOx/Al superconducting tunnel junction.The tunnel junction is coupled with a three-dimensional resonant cavity to realize 3D-transmon,and the quantum characteristics of 3D-transmon are measured at 20 mK,including the ground state to the first excited state energy level transition frequency,the rabbi oscillation,the energy relaxation time T1,etc..The test results were analyzed,and the preparation process was improved.The 3D-transmon preparation process was opened.3.A preliminary study on the multi-qubit microwave flip-chip processUsing low melting point solder as electrode material,AZ1500 photoresist was spin-coated on Si substrate and gold-plated Si substrate respectively,and electrode pattern was prepared by deep ultraviolet exposure technique.The sample was placed in liquid tin to make liquid tin fill the whole.The lithographic pattern is removed from the liquid tin to remove the liquid tin remaining on the surface of the photoresist,and finally the photoresist is stripped to obtain a better electrode sample.