Quantum Computing And Quantum Bits In Mesoscopic Systems

Quantum information science is a new field of science and technology which requires the collaboration of researchers coming from different fields of physics, mathematics, and engineering: both theoretical and applied. Quantum Computing and Quantum Bits in Mesoscopic Systems addresses fundamental aspects of quantum physics, enhancing the connection between the quantum behavior of macroscopic systems and information theory. In addition to theoretical quantum physics, the book comprehensively explores practical implementation of quantum computing and information processing devices. On the experimental side, this book reports on recent and previous observations of quantum behavior in several physical systems, coherently coupled Bose-Einstein condensates, quantum dots, superconducting quantum interference devices, Cooper pair boxes, and electron pumps in the context of the Josephson effect. In these systems, the book discusses all required steps, from fabrication through characterization to the final basic implementation for quantum computing.

Quantum Computation in Solid State Systems discusses experimental implementation of quantum computing for information processing devices; in particular observations of quantum behavior in several solid state systems are presented. The complementary theoretical contributions provide models of minimizing decoherence in the different systems. Most recent theoretical and experimental results on macroscopic quantum coherence of mesoscopic systems, as well as the realization of solid-state qubits and quantum gates are discussed. Particular attention is given to coherence effects in Josephson devices. Other solid state systems---including quantum dots, optical, ion, and spin devices---are also discussed.

This book is a snapshot of the vision shared by outstanding scientists on the key theoretical and experimental issues in Mesoscopic Physics. Quantum properties of electrons in solid state devices and transport in semiconducting and superconducting low-dimensional systems, are discussed, as well as the basis of quantum computing (entanglement, noise decoherence and read-out). Each chapter collects the material presented at a Varenna School course of last year, by leading experts in the field. The reader gets a flavour of how theorists and experimentalists are paving the way to the physical realization of solid state qubits, the basic units of the new logic and memory elements for quantum processing. He will be surprised in finding that mesoscopic solid state devices, which were invented only yesterday (think of the Single Electron Transistor, or the Cooper Pair Box) are currently used as charge-sensing applications in the equipment of frontier research laboratories. These devices contribute as probing systems to produce evidence on still unsettled questions in topics like the metal-insulator transition in disordered two dimensional systems, quantum Hall conductance in heterostructur"

This volume is an outgrowth of the Second International Workshop on Macroscopic Quantum Coherence and Computing held in Napoli, Italy, in June 2000. This workshop gathered a number of experts from the major Universities and Research Institutions of several countries. The choice of the location, which recognizes the role and the traditions of Naples in this field, guaranteed the participants a stimulating atmosphere. The aim of the workshop has been to report on the recent theoretical and experimental results on the macroscopic quantum coherence of macroscopic systems. Particular attention was devoted to Josephson devices. The correlation with other atomic and molecular systems, exhibiting a macroscopic quantum behaviour, was also discussed. The seminars provided both historical overview and recent theoretical ground on the topic, as well as information on new experimental results relative to the quantum computing area. The first workshop on this topic, held in Napoli in 1998, has been ennobled by important reports on observations of Macroscopic Quantum Coherence in mesoscopic systems. The current workshop proposed, among many stimulating results, the first observations of Macroscopic Quantum Coherence between macroscopically distinct fluxoid states in rf SQUIDs, 20 years after the Leggett's proposal to experimentally test the quantum behavior of macroscopic systems. Reports on observations of quantum behaviour in molecular and magnetic systems, small Josephson devices, quantum dots have also been particularly stimulating in view of the realization of several possible q-bits.

Quantum Computation in Solid State Systems discusses experimental implementation of quantum computing for information processing devices; in particular observations of quantum behavior in several solid state systems are presented. The complementary theoretical contributions provide models of minimizing decoherence in the different systems. Most recent theoretical and experimental results on macroscopic quantum coherence of mesoscopic systems, as well as the realization of solid-state qubits and quantum gates are discussed. Particular attention is given to coherence effects in Josephson devices. Other solid state systems---including quantum dots, optical, ion, and spin devices---are also discussed.

This book is a snapshot of the vision shared by outstanding scientists on the key theoretical and experimental issues in Mesoscopic Physics. Quantum properties of electrons in solid state devices and transport in semiconducting and superconducting low-dimensional systems, are discussed, as well as the basis of quantum computing (entanglement, noise decoherence and read-out). Each chapter collects the material presented at a Varenna School course of last year, by leading experts in the field. The reader gets a flavor, how theorists and experimentalists are paving the way to the physical realization of solid state qubits, the basic units of the new logic and memory elements for quantum processing. He will be surprised in finding that mesoscopic solid state devices, which were invented just yesterday ( think of the Single Electron Transistor, or the Cooper Pair Box) are currently used as charge-sensing applications in the equipment of frontier research laboratories. These devices contribute as probing systems to produce evidence on still unsettled questions in topics like the metal-insulator transition in disordered two dimensional systems, quantum Hall conductance in heterostructures, or Kondo conductance in quantum dots.

This book targets computer scientists and engineers who are familiar with concepts in classical computer systems but are curious to learn the general architecture of quantum computing systems. It gives a concise presentation of this new paradigm of computing from a computer systems' point of view without assuming any background in quantum mechanics. As such, it is divided into two parts. The first part of the book provides a gentle overview on the fundamental principles of the quantum theory and their implications for computing. The second part is devoted to state-of-the-art research in designing practical quantum programs, building a scalable software systems stack, and controlling quantum hardware components. Most chapters end with a summary and an outlook for future directions. This book celebrates the remarkable progress that scientists across disciplines have made in the past decades and reveals what roles computer scientists and engineers can play to enable practical-scale quantum computing.

The present book provides to the main ideas and techniques of the rapid progressing field of quantum information and quantum computation using isotope - mixed materials. It starts with an introduction to the isotope physics and then describes of the isotope - based quantum information and quantum computation. The ability to manipulate and control electron and/or nucleus spin in semiconductor devices provides a new route to expand the capabilities of inorganic semiconductor-based electronics and to design innovative devices with potential application in quantum computing. One of the major challenges towards these objectives is to develop semiconductor-based systems and architectures in which the spatial distribution of spins and their properties can be controlled. For instance, to eliminate electron spin decoherence resulting from hyperfine interaction due to nuclear spin background, isotopically controlled devices are needed (i.e., nuclear spin-depleted). In other emerging concepts, the control of the spatial distribution of isotopes with nuclear spins is a prerequisite to implement the quantum bits (or qbits). Therefore, stable semiconductor isotopes are important elements in the development of solid-state quantum information. There are not only different algorithms of quantum computation discussed but also the different models of quantum computers are presented. With numerous illustrations this small book is of great interest for undergraduate students taking courses in mesoscopic physics or nanoelectronics as well as quantum information, and academic and industrial researches working in this field.