本文關鍵詞：超導JosephsonF遂道結的制備、性能研究及超導量子比特電路的結構探討　出處：《南京大學》2015年碩士論文　論文類型：學位論文

  更多相關文章： 懸空掩膜結構 超導Al/AlO_x/Al隧道結 超導電流密度 面積歸一化電阻 超導量子比特電路的結構探討 qubit信號

【摘要】：目前作為實現(xiàn)量子計算機的物理系統(tǒng)有很多方案,在諸多方案中,基于Josephson結的超導體方案由于設計和制備的工藝比較成熟、與外界耦合較強、宏觀量子系統(tǒng)比一般量子系統(tǒng)大1000倍等優(yōu)勢而備受關注。本文主要研究了超導Al/AlOx/Al隧道結的制備工藝,并通過對隧道結的超導電流密度Jc、面積面積歸一化電阻Rc同氧化氣壓P的關系以及上、下電極的鋁薄膜厚度同Rc關系的研究來改善超導隧道結的質量。整個制備工藝簡單且能達到構建超導量子比特的要求,同時還制備出三種方案的超導量子比特。本論文的主要研究內容包括以下三個部分：1.超導Al/AlOX/Al隧道結的制備本文利用雙層光刻膠經過紫外線曝光制備出懸空掩膜結構,然后采用電子束傾斜角度的原位制備方法制備出Al/AlOX/Al隧道結,該工藝的最大優(yōu)點在于整個制備過程簡單且容易控制。此外,勢壘層是通過純度為99.99%的氧氣在下電極鋁薄膜的表面直接氧化生成,無污染；結區(qū)的長度可以通過調節(jié)蒸發(fā)角度來控制。目前,該工藝各流程的條件比較穩(wěn)定,制備出的超導Al/AlOX/Al隧道結的超導電流密度Jc已達到70A/cm2,漏電比可以控制在2%以下,均已達到構建超導量子比特的要求。2.超導Al/AlOx/Al隧道結特性研究由于Jc和能隙電壓等參數(shù)均需在極低溫條件下測量,測量過程周期較長、經濟效益低且具有不可預判性,本文系統(tǒng)地研究了影響Jc和Rc的工藝條件,實驗結果表明,Rc和Jc有一定的相關性,通過對Rc的測量可以預判Jc,同時在實驗中通過對氧化氣壓P的調節(jié)來控制Rc,從而指導實驗的進程。此外本論文還針對上、下電極薄膜的厚度同Rc的關系作了系統(tǒng)的分析,結果表明,在其他條件相同的情況下,底電極的膜厚在小于80nm范圍內變化時,將顯著影響Rc的大小,而上電極的膜厚與Rc關聯(lián)較小。3.超導量子比特電路的結構探討本文對三種超導量子比特電路結構的設計進行了嘗試,通過在制備過程中不斷改善電路的結構以及改變部分重要參數(shù),測出比較理想的qubit信號。
[Abstract]:At present, there are many schemes for the physical system to realize quantum computer. In many schemes, the superconductor scheme based on Josephson junction is more mature in design and fabrication, and has strong coupling with the outside world. The macroscopic quantum system is one thousand times larger than the conventional quantum system, and has attracted much attention. In this paper, the fabrication process of superconducting Al/AlOx/Al tunneling junctions is studied. The relationship between the superconducting current density (Jc), area normalized resistance (RC) and oxidation pressure (P) of the tunnel junction is also discussed. In order to improve the quality of superconducting tunnel junctions, the quality of superconducting tunnel junctions is improved by the study of the relationship between the thickness of aluminum film and RC of the lower electrode. The whole preparation process is simple and can meet the requirements of constructing superconducting quantum bits. At the same time, three kinds of superconducting quantum bits have been prepared. The main contents of this thesis include the following three parts:. 1. Preparation of superconducting Al/AlOX/Al tunnel junctions in this paper, the suspended mask structure was fabricated by UV exposure of double-layer photoresist. Then the Al/AlOX/Al tunnel junctions were prepared by in situ preparation of electron beam tilt angle. The biggest advantage of this process is that the whole preparation process is simple and easy to control. The barrier layer is directly oxidized by oxygen with purity of 99.99% on the surface of the lower electrode aluminum film without pollution. The length of the junction area can be controlled by adjusting the evaporation angle. At present, the conditions of each process are relatively stable. The superconducting current density J _ c of the superconducting Al/AlOX/Al tunnel junction has reached 70 A / cm ~ 2, and the leakage ratio can be controlled below 2%. The characteristics of superconducting Al/AlOx/Al tunnel junctions have been studied because the parameters such as J _ c and gap voltage need to be measured at very low temperature and the measuring process period is longer. The technological conditions affecting JC and RC are studied systematically in this paper. The experimental results show that there is a certain correlation between RC and JC, and JC can be forecasted by the measurement of RC. In addition, the relationship between the thickness of the upper and lower electrode films and RC is analyzed systematically in this paper. Under the same conditions, when the film thickness of the bottom electrode changes in the range of less than 80 nm, the size of RC will be significantly affected. The structure of superconducting quantum bit circuit is discussed. In this paper, we try to design three kinds of superconducting quantum bit circuit structure. The ideal qubit signal is obtained by improving the circuit structure and changing some important parameters.
【學位授予單位】：南京大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TM26

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本文編號：1437135