The Key Technology For Long-range Correlation Of Carbon Nanotube Quantum Dots

In recent years,quantum computing has made a lot of progress.Semiconductor quantum computing system is a potential candidate in solid-state quantum computing.However,there are many research bottlenecks in quantum computing,such as the long-range coupling of quantum bit.Semiconductor and superconducting quantum computing system mainly use superconducting microwave cavity to achieve long-range bit coupling,but the large size of superconducting microwave cavity and crosstalk between signals are not conducive to large-scale integration.At present,quantum phononics,developed on nanomechanical resonator and other systems,provides a new way for the large-scale integration of solid-state qubit.This thesis selects carbon nanotube as the main research object,and designs the series structure of multiple mechanical resonators(including quantum dot)by using the coupling structure of mechanical resonator and semiconductor quantum dot formed by carbon nanotube.The objective is to achieve the long-range coupling of quantum dots by the coherent transmission of phonon modes in mechanical resonator.Towards this goal,this thesis mainly develops the following key technologies:1.The structure of carbon nanotube series mechanical resonator(containing quantum dots)is designed.The fundamental properties of carbon nanotube quantum dots and mechanical resonator are characterized by extremely low temperature characterization technique.The coupling between quantum dots and mechanical resonator is also studied.2.An extremely low temperature two-channel noise correlation measurement system is built,which is suitable for noise correlation detection of two-channel quantum system.The measurement system includes RLC,cryogenic amplifier and room temperature amplifier.The equivalent input noise of the system reaches 0.711 nV/(?)and 1.609 nV/(?),which is close to 0.4 nV/(?)of international counterparts.Using these techniques,the single and double quantum dots structure of carbon nanotube are controlled by DC modulation,and the Coulomb block phase diagram and stability phase diagram are obtained.The linear and nonlinear response of the mechanical resonator driven by microwave is measured.The softening and nonlinear enhancement of the mechanical resonator due to the electron-phonon interaction are observed.The research in this thesis lays a foundation for the phonon-assisted quantum bit long-range coupling architecture.