Preparation And Measurement Of Superconducting Qubit Devices

The:fundamental interaction between light and matter is studied in cavity quan-tum elecltrodynamics(QED).If an atom and a photon interact with eachother in a well-isolated resonant cavity,they will be strongly coupled without dissipating energy.In this strong coupling,the atom will constantly absorb and release a single quantum en?ergy.The photon and atom lose their properties and form a new eigenstate,the quantum superposition state of matter and light.By analogy,circuit QED is a novel cavity QED chip implementation.It provides the possibility of strong coupling between artificial atoms-superconducting qubits and photons in 3D or coplanar waveguide resonators.This new solid state method for studying the interaction between matter and light can artificially control and change the parameters,which opens the door for new quantum optical experiments.In addition,coupling multiple superconducting qubit resonators with a single quantum bus is a promising hardware architecture for scalable quantum information processors.In this paper,I will discuss the theoretical model of circuit QED composed of alu-minum/aluminum oxide Josephson junction qubits integrated into the superconducting coplanar waveguide resonator,and introduce in detail the high-quality resonator and Josephson junction made by photolithography,wet etching and aluminum thin film evaporation.The ability to implement superconducting qubits with precisely controlled properties,such as Josephson energy and charge energy,is crucial to defining the struc-ture of specific qubit energy levels.In general,in order to conduct specific circuit QED experiments,the maximum transition frequency,anharmonic degree,charge dispersion and the coupling strength between the qubit and the cavity must be controlled through repeated tests.Therefore,a set of very strict fabrication process is required:calibration of electron beam exposure dose and dual-angle evaporation to prepare Josephson junc-tion oxidation time and other process parameters;The electrical properties and material properties of the Josephson junction,such as the tunnel resistance at room temperature and the resistance change with time caused by the oxidation process,were studied.Con-sidering the time limitation of the decoherence of superconducting qubits,we consider using adiabatic shortcut technology to simulate the evolution of qubit states,so that the qubit can be controlled quickly and stably in a limited time.On the other hand,we try to improve the decoherence time according to the disadvantage of magnetic flux qubits.