Fabrication And Readout Of Quantum State In Phonon-superconducting Quantum Circuits Hybrid System

Quantum computation based on superconducting qubits is a fast developing field.With increase of qubit integration and control accuracy,the information process approaches the threshold for demonstrating quantum advantage.Based on this,the hybrid system of superconducting qubits and other systems has also received extensive attention.Sound is an excellent carrier for transmitting information in solid state in the gigahertz band.Compared with microwave signal,low wave speed and short wavelength acoustic signal can address a single qubit on a highly integrated superconducting quantum chip alone and there is little signal crosstalk to other qubits that do not want to operate.Therefore,surface acoustic wave and body wave modulated superconducting quantum information processing is expected to solve the unavoidable problem of crosstalk in microwave dynamic quantum computing.The combination of phonon and superconducting quantum circuit has unique advantages in quantum computing.Acousticsuperconducting quantum circuit hybrid system is becoming a new frontier of quantum information technology,which provides a new research field for acoustics and opens up a new platform for quantum information processing based on phonon regulated superconductivity.In this paper,the preparation and realization of the coupling system of superconducting qubit and phonon are described from four aspects.Firstly starting from the sound system,we explored the basic principle design and process method of the surface acoustic wave resonator.Through the feedback of the variable parameter normal temperature test and low temperature test on the lithium niobate substrate,we verified the basic properties of the surface acoustic wave resonator and screened out the high frequency and high quality factor of the surface acoustic wave resonator.In order to improve the resolution of quantum state measurement,the parametric amplifier is studied from the point of view of design and technology.By improving the design,adding impedance converter and redesigning the process flow,we have successfully extended the narrowband amplifier to wideband.Then we focused on the design principle of superconducting qubit,the process preparation process and the process improvement scheme: using the resin developer to etch the resonator to improve the etching process,simplify the process flow and increase the sample yield;The frequency fluctuation of Josephson junction was reduced by studying the relationship between oxidation time and pressure and critical current density,and the fluctuation of critical current was controlled to 0.8%.The decoherence time of superconducting qubit was increased by an order of magnitude by optimizing the surface treatment,increasing the etching Angle and resetting the packaging method.Finally,we propose two new coupling schemes to integrate the superconducting qubits and surface acoustic wave resonators on different chips into the same sample box,and the test results verify the feasibility of the proposed scheme.The scheme has certain extensibility and lays a certain foundation for the large-scale and high integration quantum acoustic chips in the future.