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".