| Superconducting Josephson circuits based on Josephson tunnel junctions have become the mainstream of solid-state superconducting qubit chips.However,the amplification of microwave signal on a single photon level is very harsh on the noise performance of the amplifier in the readout circuit,which needs to reach the quantum limit level.Parametric amplifiers based on the nonlinearity of nondissipative Josephson junction LC circuit are designed,the noise level can approach the quantum limit,and the single-shot high fidelity nondestructive readout measurement of the qubit is realized.In this thesis,the basic theory of Josephson parametric amplifier using superconducting coplanar waveguide cavity circuit is studied.The design,fabrication process,and characterization of Josephson parametric amplifier with various bandwidths are developed.The main research contents and innovative achievements include the following aspects:1.The mechanism of Josephson parametric amplification is analyzed theoretically,including nonlinear response,bandwidth gain,quantum-limit noise level,and so on.Based on the study of the theoretical model,a narrow-band superconducting Josephson parametric amplifier based on coplanar waveguide cavity is designed,and a predictable and reproducible preparation process is explored and formed.In the frequency range of 4 ?12 GHz,Josephson parametric amplifier with tunable frequency can be quickly designed and prepared.Moreover,the measurement chain of the device is built,and the bandwidth,gain,noise,and dynamic range of the amplifier are characterized.In addition,The coherent signal phase shift caused by the interaction between the parametric cavity and external transmission line is observed experimentally and explained theoretically.The coherent signal squeezing can be controlled accurately by adjusting the DC flux bias and the operating point of the resonator.As one of the most important practical requirements,the single-shot readout measurement of 3D cavity transmon using JPA is carried out.2.The devices of coupled resonators with parametric amplification are designed,prepared,and characterized.The controllable coupling between two resonators is realized by modulating the SQUID using the biased flux line.The bandwidth characteristics of the amplifier are studied.The results show that the coupling scheme can be pumped using twice or combined frequencies,and the parametric amplification and conversion amplification can be realized.3.Due to the impedance mismatch between the external signal and the nonlinear LC resonant circuit,the bandwidth of the parametric amplifier is limited by the line-width of the cavity.In this work,by using Si Nx as a dielectric layer and the superconducting metal plate to cover the central conductor of transmission line and reference ground,a new method is proposed to enhance the capacitive coupling between coplanar waveguide line and reference ground.A broadband superconducting Josephson parametric amplifier with gradual impedance matching is designed.The experimental results show that the gain of the amplifier can reach25 d B and the bandwidth is close to 100 MHz.By adjusting the operating point,the gain can exceed 17 d B with a bandwidth of 400 MHz.The noise is close to the quantum limit,which can meet the requirements of multi-qubits measurement.The research can satisfy the critical requirements of signal amplification with quantum limit noise performance in a non-destructive measurement scheme of a superconducting qubit with high fidelity,and provide reliable several photon level amplification for further research in many fields of the superconducting qubit. |
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