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、纽约州立大学斯托尼布鲁克分校和日本关西高级研究中心（KARC）的一个国际团队，专注于一种更有前途的固态量子比特方法，即基于约瑟夫森结（JJ）的超导通量和电荷量子比特。 将超导JJ器件用于量子位应用（例如量子计算）需要解决许多重大挑战：优化超导材料参数和相应的结制造方法;确定制备和操纵相干量子态的合适方法;开发测量协议;量子位和量子门的设计;最后，开发针对JJ系统的错误预防/纠正方案。 为此，将制造基于铌、氮化铌和铝的高质量JJ量子比特，并在时域和频域研究其相干特性。 量子位退相干与材料性质和制造方法之间的相关性将被系统地研究。 此外，将开发算法来减少和减轻退相干和门误差。 该项目涉及国际教育和培训的学生从本科到博士后副水平。 参与者接受凝聚态和低温物理学领域一系列尖端技术的基础培训。 这为他们在商业，工业和政府的职业生涯做好了准备;特别是在量子信息科学和技术的新兴领域，这是一个有助于国家竞争力和国土安全的领域。 这个信息技术研究（ITR）项目汇集了来自堪萨斯大学、纽约州立大学斯托尼布鲁克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设备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。 如果实现了这种量子控制，预计这种计算机将能够解决许多非常重要的问题，这些问题对于现有或计划中的经典计算机来说几乎是难以解决的。 其中之一是非常大的数字的因式分解问题-密码学的关键。 除此之外，简单地理解和控制量子系统是非常重要的，几乎是直接的技术兴趣。 量子计算机发展的一个巨大障碍是要求计算机在整个计算过程中能够保持所有器件之间的量子力学相干性。 宏观设备元件与外部世界或环境的不可避免的相互作用可以迅速破坏这种一致性，事实上，这是量子效应在日常经验中无法观察到的主要原因。 该项目将利用超导材料的高度相干态来形成量子计算机的基本元素，即所谓的量子比特。 这种方法也将允许使用集成电路技术来将计算机缩放到有用的尺寸。 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-一个被称为“量子信息科学”的迅速崛起的重要领域。

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".