本文關(guān)鍵詞：量子點(diǎn)中的自旋量子比特　出處：《中國(guó)科學(xué)技術(shù)大學(xué)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 量子點(diǎn) 自旋量子比特 自旋態(tài)讀取 自旋阻塞 多電子編碼

【摘要】：半導(dǎo)體量子點(diǎn)中的自旋量子比特所具有的長(zhǎng)相干時(shí)間以及易于集成的特點(diǎn)使其受到了廣泛的關(guān)注。本論文致力于GaAs雙量子點(diǎn)中自旋量子比特的研究,主要內(nèi)容包括:1、簡(jiǎn)要介紹了量子計(jì)算的背景和概念。利用常相互作用模型對(duì)量子點(diǎn)中的一些基本現(xiàn)象作了解釋,包括單量子點(diǎn)中的庫(kù)倫振蕩,庫(kù)倫阻塞,雙量子點(diǎn)中的三相點(diǎn),偏壓三角形等。2、對(duì)單電子自旋量子比特作了簡(jiǎn)單的原理分析。詳細(xì)介紹了兩電子自旋單態(tài)三重態(tài)量子比特的哈密頓量,以及實(shí)驗(yàn)細(xì)節(jié),包括觀測(cè)自旋阻塞的兩種方式以及表征系統(tǒng)的方法,最后介紹了兩個(gè)經(jīng)典的實(shí)驗(yàn)以及我們的實(shí)驗(yàn)結(jié)果。3、利用雙量子點(diǎn)的不對(duì)稱性在三電子(1,2)-(2,1)電荷躍遷區(qū)域觀測(cè)到了四重態(tài)的自旋阻塞。利用這種自旋阻塞我們實(shí)現(xiàn)了自旋四重態(tài)和兩重態(tài)之間的Landau-Zener-Stuckelberg干涉和交換振蕩。最后補(bǔ)充了我們另外兩個(gè)奇數(shù)電子區(qū)(1,2)-(0,3)和(1,6)-(0,7)的實(shí)驗(yàn)結(jié)果。4、在偶數(shù)電子區(qū)(1,3)-(0,4)區(qū)域的交換振蕩實(shí)驗(yàn)中發(fā)現(xiàn)了一種信號(hào)放大機(jī)制。分析并且實(shí)驗(yàn)驗(yàn)證該機(jī)制。設(shè)計(jì)了一種控制放大過(guò)程的方法,并利用此方法提取出不同自旋態(tài)的隧穿速率。5、對(duì)雙量子點(diǎn)進(jìn)行輸運(yùn)研究。在五個(gè)連續(xù)的電荷躍遷區(qū)域觀察到了自旋阻塞現(xiàn)象。通過(guò)分析數(shù)據(jù)確定了每個(gè)區(qū)域的阻塞自旋態(tài)。本文的主要?jiǎng)?chuàng)新點(diǎn)有:1、首次在雙量子點(diǎn)(1,2)-(2,1)區(qū)域觀察到了自旋阻塞現(xiàn)象,并利用該現(xiàn)象實(shí)現(xiàn)了自旋態(tài)的讀取,以及演示了相干操作。利用在此區(qū)域發(fā)展的方法,我們對(duì)其他奇數(shù)區(qū)進(jìn)行了探索,并得到了類似的結(jié)果。我們的結(jié)果和實(shí)驗(yàn)方法將對(duì)未來(lái)探索多電子自旋量子比特編碼具有啟發(fā)意義。2、發(fā)現(xiàn)了一種新的自旋到電荷轉(zhuǎn)換機(jī)制。該機(jī)制在用來(lái)讀取自旋量子比特的狀態(tài)時(shí)產(chǎn)生比傳統(tǒng)的基于自旋阻塞的方法更強(qiáng)的信號(hào)。在實(shí)驗(yàn)中我們實(shí)現(xiàn)了兩倍的放大。我們闡明了如何用一個(gè)簡(jiǎn)單的方案實(shí)現(xiàn)放大倍數(shù)的顯著提升。3、首次在連續(xù)的多個(gè)電荷躍遷區(qū)域觀察到自旋阻塞現(xiàn)象。尤其是奇數(shù)電子區(qū)自旋阻塞,結(jié)合平面雙量子點(diǎn)強(qiáng)大的可控性,為研究電子自旋與核自旋相互作用提供了新的有力的工具。
[Abstract]:Spin quantum bits in semiconductor quantum dots have attracted wide attention due to their long dry time and easy integration. This thesis is devoted to the research of spin quantum bits in GaAs double quantum dots. The main contents include: 1. The background and concept of quantum computation are briefly introduced. Some basic phenomena in quantum dots are explained by using the constant interaction model, including Coulomb oscillation and Coulomb blocking in single quantum dots. In this paper, the simple principle of single-electron spin quantum bit is analyzed, and the Hamiltonian of two-electron spin triplet quantum bit is introduced in detail. And the details of the experiment, including the two ways of observing spin blocking and the method of characterizing the system. Finally, two classical experiments and our experimental results are introduced. The asymmetry of the double quantum dots is used in the three-electron system. 1). In the charge transition region, the spin blocking of the quaternary states is observed. Using this spin blocking, we have realized the Landau-Zener-Stuckelberg interference between the spin quadruple states and the double states. And exchange oscillations. Finally, we add two other odd electron regions. 1. The experimental results of 2 ~ (-0) ~ (3) and 1 ~ (1) ~ (6) ~ (~ (0) ~ (7))) are found in the even number electron region of ~ (1) ~ (3) ~ (-) ~ (0). 4) A signal amplification mechanism is found in the region switching oscillation experiment. The mechanism is analyzed and verified experimentally. A method to control the amplification process is designed. The tunneling rate of different spin states is extracted by this method. In this paper, the spin blocking phenomenon is observed in five continuous charge transition regions. The blocking spin states of each region are determined by analyzing the data. The main innovation point of this paper is: 1. Spin blocking has been observed for the first time in the region of double quantum dots (TQDs), and the reading of spin states has been realized by using this phenomenon, and the coherent operation has been demonstrated. The method developed in this region has been used. We have explored other odd regions and obtained similar results. Our results and experimental methods will be instructive for exploring multi-electron spin quantum bit coding in the future. A new spin to charge conversion mechanism is found, which produces stronger signals than the traditional spin-blocking method when used to read states from spin quantum bits. In the experiment, we achieve double amplification. We illustrate how to achieve a significant increase in magnification by 3. 3 using a simple scheme. Spin blocking is observed for the first time in successive charge transition regions, especially in odd electron regions, combined with the strong controllability of planar double quantum dots. It provides a new powerful tool for studying the interaction between electron spin and nuclear spin.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：O471.1

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本文編號(hào)：1393882