三维传输子量子比特中Autler-Townes效应的研究

发布时间：2018-05-28 21:36

本文选题：3D + transmon　；参考：《南京大学》2017年硕士论文

【摘要】：超导量子比特作为一种固态的量子计算机的实现方式,由于其与半导体的制备技术相兼容,容易集成和可扩展的优势,在国际上受到了广泛的研究和关注。近年来由于量子比特的退相干时间逐渐增长,使得以超导量子比特为基本计算单元的超导量子计算机的实现越来越近。本文紧跟国际研究的热点,以Yale提出的三维传输子量子比特(3D transmon)为研究对象,对其中的有关量子特性开展了研究,主要研究内容包括:1、通过三维谐振腔和约瑟夫森结的耦合,实现了 3D transmon。并搭建了量子比特的测量系统,以Triton400稀释制冷机为极低温平台,通过常温、低温下的信号控制、噪声隔离和线路切换,建立了高同步、高采样、高速读取的测量系统。利用亮态读出方法,表征了多个量子比特的参数,包括能级跃迁频率、拉比震荡、能量弛豫时间和相位退相干时间等。2、在3D transmon中分别表征了基态和第一激发态、第二激发态的双光子跃迁频率,并在耦合场和探测场的不同组合中,分别利用单光子跃迁与双光子跃迁对Autler-Townes分裂现象(ATS)继续探测。比较探测场和耦合场的强度,得出了两种探测中,ATS分裂大小和耦合场强度的关系。通过理论计算解得了在ATS现象发生时的三阶密度矩阵,和实验结果符合的很好。3、通过任意波形发生器生成不同跳变频率的RTN,并用该RTN对3D transmon的耦合场进行调制,我们研究了随机电报噪声对于3D transmon中ATS现象的影响,观察到了 RTN在高跳变频率下对于能级之间的动态平均的现象,并讨论了动态平均临界点和耦合场功率的关系。通过理论计算得出了和实验结果相符的结论。
[Abstract]:As a kind of solid state quantum computer, superconducting quantum bit has been widely studied and paid attention in the world because of its compatibility with semiconductor preparation technology, easy integration and expandable advantages. In recent years, the realization of superconducting quantum computer with superconducting quantum bits as the basic computing unit is getting closer due to the increasing time of decoherence of quantum bits. In this paper, following the international research focus, we have studied the quantum properties of three-dimensional transmisson quantum bits proposed by Yale. The main research contents include: 1, the coupling of three-dimensional resonator and Josephson junction. 3D transmonn is realized. The measurement system of quantum bit is set up. The measurement system of high synchronization, high sampling and high speed reading is set up through signal control at room temperature and low temperature, noise isolation and circuit switching using Triton400 dilution refrigerator as the very low temperature platform. The parameters of several quantum bits, including energy level transition frequency, rabbi oscillation, energy relaxation time and phase decoherence time, are characterized by bright state readout method. The ground state and the first excited state are characterized in 3D transmon, respectively. The two-photon transition frequency of the second excited state and the single photon transition and two-photon transition are used in different combinations of the coupling field and the detection field respectively to detect the Autler-Townes splitting phenomenon. By comparing the intensity of the probe field and the coupling field, the relationship between the splitting size and the coupling field intensity of the two kinds of probes is obtained. The third-order density matrix when ATS phenomenon occurs is solved by theoretical calculation, which is in good agreement with experimental results. RTNs with different jump frequencies are generated by arbitrary waveform generator, and the coupling field of 3D transmon is modulated by the RTN. We study the effect of random Telegraph noise on the ATS phenomenon in 3D transmon, observe the dynamic averaging between energy levels of RTN at high hopping frequency, and discuss the relation between the critical point of dynamic mean and the power of coupling field. By theoretical calculation, the conclusion is in agreement with the experimental results.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O413

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