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.

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.

As the end of the nineteenth century neared, it was clear to many in the physics community that if only Newton's equations plus Maxwell's equations could be solved adequately, there would really be nothing very new in physics on a fundamental level. Then came relativity and quantum mechanics. As we now approach the end of the twentieth century, it is clear to many in the physics community that if one could adequately solve somebody's gauge field theory (or somebody else's string model), then nothing fundamentally new would ever again enter into physics. To others in the physics community, it is somewhat doubtful that our present physical understanding of the world, especially of quantum mechanics, has reached such a pinnacle.This conference was organized to discuss the present state of affairs in our knowledge, both experimental and theoretical, of the basic tenets of quantum mechanics. Many fields of physics in which quantum mechanics plays a central role were included: (i) atomic and molecular beams; (ii) photon beams; (iii) atomic interference in atom-surface physics and atom wire physics; (iv) Bose-condensed systems; (v) quantum '1/f' noise; (vi) quantum electrodynamics effects in water, colloidal systems and biological systems; (vii) quantum interference in neutrino physics; (viii) periodic-in-time driven quantum systems; (ix) superconducting quantum circuits; and (x) quantum computer circuit elements.The large variety of different topics, all of current importance, allowed for various viewpoints that are usually not present when conferences devoted to narrower topics are held. The cross-fertilization of ideas was greatly appreciated by the participants, and will be of equal interest to the reader of the proceedings.

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.

As the end of the nineteenth century neared, it was clear to many in the physics community that if only Newton's equations plus Maxwell's equations could be solved adequately, there would really be nothing very new in physics on a fundamental level. Then carne relativity and quantum mechanics. As we now approach the end of the twentieth century, it is clear to many in the physics community that if one could adequately solve somebody's gauge field theory (or somebody else's string model), then nothing fundamentally new would ever again enter into physics. To others in the physics community, it is somewhat doubtful that our present physical understanding of the world, especially of quantum mechanics, has reached such a pinnacle. This conference was organized to discuss the present state of affairs in our knowledge, both experimental and theoretical, of the basic tenets of quantum mechanics. Many fields of physics in which quantum mechanics plays a central role were included: (i) atomic and molecular beams; (ii) photon beams; (iii) atomic interference in atom-surface physics and atom wire physics; (iv) Bose-condensed systems; (v) quantum "1/f" noise; (vi) quantum electrodynamics effects in water, colloidal systems and biological systems; (vii) quantum interference in neutrino physics; (viii) periodic-in-time driven quantum systems; (ix) superconducting quantum circuits; and (x) quantum computer circuit elements. The large variety of different topics, all of current importance, allowed for various viewpoints that axe usually not present when conferences devoted to narrower topics are held. The cross-fertilization of ideas was greatly appreciated by the participants, and will be of equalinterest to the reader of the proceedings.

Exploring the Quantum/Classical Frontier - Recent Advances in Macroscopic Quantum Phenomena