可调半波长超导共面波导谐振器的研究

发布时间：2019-06-10 10:06

【摘要】：随着对计算速度和存储容量越来越高的要求,经典计算机终将不能满足人们的需求,量子计算机必然会成为时代发展的产物。超导量子比特被大量的实验证实是实现量子计算的最佳方案,而具有低损耗、高Q值等优势的超导共面波导谐振器(SCPWR)可以对量子比特的状态进行测量,且可以作为一种媒介来实现多个量子比特之间的耦合。同时,为了实现对超导量子比特耦合的灵活控制,研制谐振频率原位可调节的谐振器显得尤为迫切。本文介绍的可调半波长开路SCPWR,是通过在谐振器的中心导体内嵌入dc-SQUID来实现频率可调的。文章从可调SCPWR的研究背景、相关基本理论、设计思路、制备过程和实验测量结果与理论分析几个方面进行了具体阐述：第一章由量子计算引出超导量子比特,介绍了与超导电路密切关联的约瑟夫森结的性质与RSJ模型,以及超导量子干涉仪上的电流随外加磁通的调制关系。然后,介绍了超导谐振腔的相关研究背景和发展历程,并介绍了超导共面波导谐振器的应用及它的基本结构。接着介绍了本文的研究对象---可调SCPWR,简述了三种国内外研究者实现频率可调的方案。第二章介绍了共面波导(CPW)的结构和基本参数的计算方法。由于本文介绍的半波长开路谐振器,在谐振时表现为并联谐振电路的特性,所以紧接着介绍了并联谐振电路和半波长开路传输线的基本特性。随后介绍了谐振器的电容耦合、阻抗匹配和矢量网络分析仪的基本原理,这些都是谐振器的设计和测量过程中需要注意的事项。第三章介绍了通过HFSS和ADS两种软件,设计和仿真验证谐振器。详述了深紫外曝光和电子束蒸发相结合的微加工工艺制备谐振器的步骤。介绍了提供极低温环境的Triton 400稀释制冷机的工作原理以及在制冷机上测量谐振器的线路图。第四章介绍了无dc-SQUID的谐振器和约瑟夫森结I._V特性的测量结果,验证了其性能良好。在此基础上,用矢量网络分析仪测量了嵌入一个或者三个dc-SQUID的可调SCPWR的谐振频率随外加磁通变化关系曲线,并进行理论分析,实验结果和理论值吻合较好。进一步得到了谐振器Q值与外加磁通的关系,并进行了相关理论分析。
[Abstract]:With the increasing requirements for computing speed and storage capacity, classical computers will not be able to meet the needs of people, quantum computers will inevitably become the product of the development of the times. Superconducting qubit has been proved by a large number of experiments to be the best scheme for quantum computing, and superconducting coplanar waveguide resonator (SCPWR), which has the advantages of low loss and high Q value, can measure the state of qubit. And it can be used as a medium to realize the coupling between multiple qubits. At the same time, in order to realize the flexible control of superconducting quantum bit coupling, it is particularly urgent to develop a resonator with adjustable resonance frequency in situ. The adjustable half-wavelength open-circuit SCPWR, introduced in this paper is frequency adjustable by embedding dc-SQUID into the central conductor of the resonator. In this paper, the research background, related basic theories, design ideas, preparation process, experimental measurement results and theoretical analysis of adjustable SCPWR are described in detail: in the first chapter, superconducting qubits are derived from quantum computing. The properties of Josephson junction, which is closely related to superconducting circuits, and the RSJ model, as well as the modulation relationship between the current on superconducting quantum interferometers and the applied flux, are introduced. Then, the research background and development of superconducting resonator are introduced, and the application and basic structure of superconducting coplanar waveguide resonator are introduced. Then it introduces the adjustable SCPWR, which is the research object of this paper, and briefly describes three schemes for domestic and foreign researchers to realize adjustable frequency. In chapter 2, the structure and calculation method of basic parameters of coplanar waveguide (CPW) are introduced. Because the half-wavelength open-circuit resonator introduced in this paper shows the characteristics of parallel resonant circuit in resonance, then the basic characteristics of parallel resonant circuit and half-wavelength open-circuit transmission line are introduced. Then the basic principles of capacitance coupling, impedance matching and vector network analyzer of resonator are introduced, which are the matters needing attention in the design and measurement of resonator. In the third chapter, the design and simulation of resonator are introduced by HFSS and ADS. The steps of fabricating resonator by micro-machining process of deep ultraviolet exposure and electron beam evaporation are described in detail. This paper introduces the working principle of Triton 400 dilution refrigerator which provides very low temperature environment and the circuit diagram of measuring resonator on the refrigerator. In chapter 4, the measurement results of I. V characteristics of dc-SQUID-free resonator and Josephson junction are introduced, and the results show that the performance of the resonator and Josephson junction is good. On this basis, the relationship between the resonant frequency of adjustable SCPWR embedded with one or three dc-SQUID and the applied flux is measured by vector network analyzer, and the theoretical analysis is carried out. The experimental results are in good agreement with the theoretical values. The relationship between the Q value of the resonator and the external flux is obtained, and the related theoretical analysis is carried out.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN751.2;O413

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