ITR: Superconducting Qubits and Qugates for Scalable Quantum Computing

这个信息技术研究（ITR）项目汇集了来自堪萨斯大学，纽约州立大学石溪分校和日本关西高级研究中心（KARC）的国际团队，专注于固态量子比特的一种更有前途的方法，即基于约瑟夫森结（JJs）的超导通量和电荷量子比特。将超导JJ器件用于量子比特应用，如量子计算，需要解决一些主要挑战：优化超导材料参数和相应的结制造方法；确定相干量子态的制备和操作的合适方法；制定测量方案；量子比特和量子门的设计最后，开发针对JJ系统的错误预防/纠正方案。为此，将制备基于铌、氮化铌和铝的高质量JJ量子比特，并研究它们在时间和频域的相干性。量子比特退相干与材料性质和制造方法之间的关系将被系统地研究。此外，算法将开发，以减少和减轻退相干和门误差。该项目涉及本科至博士后阶段学生的国际教育和培训。参与者接受一系列凝聚态和低温物理前沿技术的基础培训。这为他们在学术界、工业界和政府的职业生涯做好了准备；特别是在量子信息科学与技术这一新兴领域，这一领域有助于提高国家竞争力和国土安全。这个信息技术研究（ITR）项目汇集了来自堪萨斯大学、纽约州立大学石溪分校和日本关西高级研究中心（KARC）的国际团队，专注于寻求实用量子计算机所面临的几个关键问题。这种新型计算机依赖于控制器件元件中的量子力学状态，而不是原子和分子中不受控制的电子运动状态。如果这种量子控制得以实现，预计这种计算机将能够解决许多非常重要的问题，而这些问题对于现有或计划中的经典计算机来说实际上是难以解决的。其中之一是对非常大的数字进行因数分解的问题——这是密码学的关键。除此之外，仅仅理解和控制量子系统就具有重大的基础和几乎直接的技术利益。量子计算机发展的一个巨大障碍是要求计算机能够在整个计算过程中保持其所有设备元素之间的量子力学相干性。宏观器件元件与外部世界或环境不可避免的相互作用会迅速破坏这种相干性，事实上，这也是量子效应在日常生活中无法观察到的主要原因。这个项目将利用超导材料的高度相干状态来形成量子计算机的基本元素，即所谓的量子位。这种方法还允许使用集成电路技术将计算机缩放到一个有用的尺寸。一个主要的努力将是调查和解决制造和设计问题，以尽量减少退相干。学生和博士后将接受最先进的制造和测量技术的培训，以及宏观系统中退相干的基本理论，这是一个迅速崛起的重要领域，被称为“量子信息科学”。

This Information Technology Research (ITR) project brings together an international team from the University of Kansas, SUNY at Stony Brook, and the Kansai Advanced Research Center (KARC), Japan to focus on one of the more promising approaches to solid-state qubits, viz. superconducting flux and charge qubits based on Josephson junctions (JJs). The use of superconducting JJ devices for qubit applications, such as quantum computation, requires resolution of a number of major challenges: Optimizing superconducting materials parameters and corresponding junction fabrication methods; Identification of suitable methods for preparation and manipulation of coherent quantum states; Development of measurement protocols; Design of qubit and quantum gates; finally, Development of error-prevention/correction schemes specific to JJ systems. To this end, high quality JJ qubits based on niobium, niobium nitride, and aluminum will be fabricated and their coherence properties investigated in time and frequency domains. Correlations between qubit decoherence and material properties and fabrication methods will be systematically investigated. In addition, algorithms will be developed to reduce and mitigate decoherence and gate errors. The project involves international education and training for students from the undergraduate to post-doctoral associate level. The participants receive fundamental training in a range of cutting edge techniques in condensed matter and low temperature physics. This prepares them for careers in academe, industry and government; particularly in the emerging area of quantum information science and technology, a field that contributes to national competitiveness and homeland security. This Information Technology Research (ITR) project brings together an international team from the University of Kansas, SUNY at Stony Brook, and the Kansai Advanced Research Center (KARC), Japan to focus on several key problems confronting the quest for practical quantum computers. This new class of computers depends upon controlling quantum mechanical states in device elements, as opposed to the uncontrolled electron states of motion in atoms and molecules. If this quantum control is achieved, such computers are predicted to be able to solve a number of very important problems that are virtually intractable for existing or projected classical computers. One of these is the problem of factoring of very large numbers-a key to cryptography. Beyond this, simply understanding and controlling a quantum system is of great fundamental and almost immediate technological interest. An enormous obstacle to the development of quantum computers is the requirement that the computer be able to maintain the quantum mechanical coherence among all its device elements throughout a calculation. Inevitable interactions of macroscopic device elements with the external world, or environment, can rapidly destroy this coherence and are, in fact, the major reason why quantum effects are not observed in everyday experiences. This project will make use of the highly coherent state of a superconducting material to form the basic element of a quantum computer, a so-called, qubit. This approach will also permit the use of integrated circuit technology to scale the computer to a useful size. A major effort will be to investigate and solve the fabrication and design issues to minimize decoherence. Students and post-docs will receive training in the state-of-the-art fabrication and measurement technology, as well as the underlying theory of decoherence in macroscopic systems-a field of rapidly emerging importance known as "quantum information science".