# Quantum Coherence and Decoherence

**By**

- K. Fujikawa, The University of Tokyo, Saitama, Japan
- Y.A. Ono, Hitachi Ltd., Saitama, Japan

Just as in the pervious five symposia, the aim of this symposium was to link the recent advances in technology with fundamental problems in quantum mechanics. It provided a unique interdisciplinary forum where scientists with different backgrounds were given the opportunity to discuss basic problems of common interest in quantum science and technology from various aspects. This included not only an examination of the topic in terms of quantum optics and mesoscopic physics, but also in terms of the physics of precise measurement, macroscopic quantum phenomena, complex systems, and other fundamental problems in quantum physics. Two new important fields were also dealt with - the field of quantum computing, including quantum teleportation, quantum information, and cryptography, and the field of laser cooling, including Bose-Einstein condensation and atom interferometry.

The resulting proceedings will be welcomed both as a good introductory book on quantum coherence and decoherence by newcomers to the field and as a reference book for experts in this dynamic area.

View full descriptionThe resulting proceedings will be welcomed both as a good introductory book on quantum coherence and decoherence by newcomers to the field and as a reference book for experts in this dynamic area.

### Book information

- Published: March 2000
- Imprint: ELSEVIER
- ISBN: 978-0-444-50091-5

### Table of Contents

Preface. Opening address (H. Fukuyama). Welcome address (K. Miyauchi).**Quantum Computing, Quantum Teleportation, and Entanglement.**Decoherence and recoherence in quantum computation (D.P. DiVincenzo, A. Ekert). Engineering entanglement between atoms and photons in a cavity: non-locality, Schrödinger cats and decoherence (S. Haroche). Three-and four-photon correlations and entanglement: quantum teleportation and beyond (A. Zeilinger). Quantum manipulations of small Josephson junctions and the measurement process performed with a single-electron transistor (A. Shnirman, Y. Makhlin, G. Schön). Extraction of NMR quantum computation signal with parity gate (M. Kitagawa). Quantum logical diagram of quantum computing evolution (H. Matsuda, D.W. Cohen). A generalized EPR problem and quantum teleportation (A. Motoyoshi et al.). Purification of multi-particle entanglement (M. Murao et al.).

**Quantum Information and Cryptography.**Quantum cryptography and magic protocols (N. Imoto, M. Koashi, K. Shimizu). Quantum entanglement for secret sharing and telesplitting (A. Karlsson et al.). Communication channels secured from hidden eavesdropping via transmission of entangled photon pairs (K. Shimizu, N. Imoto). Quantum communication of bits by the polarization of photons (M. Matsuoka, T. Yamamoto, A. Motoyoshi). Optimal broadcasting of quantum information via teleportation (M. Murao et al.). Semiconductor-based quantum information: noiseless encoding in quantum-dot arrays (P. Zanardi, F. Rossi).

**Quantum Optics.**Quantum information enabled by quantum optics (H.J. Kimble). Manipulation of quantum statistics in mesoscopic experiments (Y. Yamamoto). Extension of nonlocal response theory to Raman process (H. Ajiki, K. Cho). Quantum Maxwell-Bloch equations for spontaneous emission in semiconductor lasers (O. Hess, H.F. Hofmann). Quantum control of atomic systems by time-resolved homodyne detection of spontaneous emission (H. F. Hofmann et al.).

**Laser Cooling, Ion Trapping, and Atom Interferometry.**Quantum computation, spectroscopy of trapped ions, and Schrödinger's cat (D.J. Wineland et al.). Atom interferometry (F. Shimizu). Multiple atomic beam interference in the Ramsey-Bordè interferometer with multiple traveling laser beams (A. Morinaga, T. Aoki). Sympathetically laser-cooled mass spectroscopy using Ba+ ions (I. Waki, T. Baba, D. Wang).

**Bose-Einstein Condensation.**Measurements of relative phase and quantum beat note between Bose-Einstein condensates (D.S. Hall et al.). Probing quantum statistical mechanics with Bose gases: nontrivial order parameter topology from a Bose-Einstein quench (J.R. Anglin, W.H. Zurek). Nonequilibrium time evolution of the condensed state of a fixed number of interacting bosons (A. Shimizu, J. Inoue, T. Miyadera). Macroscopic quantum tunneling of a Bose-Einstein condensate with attractive interaction: fate of a false vacuum (M. Ueda). Collective excitations of a trapped Bose-Einstein condensate: a variational sum-rule approach (T. Kimura, H. Saito, M. Ueda). Quantum structure of three coupled atomic Bose-Einstein condensates (K. Nemoto, W.J. Munro, G.J. Milburn).

**Mesoscopic Magnets.**Macroscopic quantum tunneling in magnetic systems (E.M. Chudnovsky). Quantum tunneling in magnetic molecules and single particles (L.Thomas et al.). Magnetic and transport properties of sub-micron ferrromagnetic wires (Y. Otani et al.). Electronic transport properties in mesoscopic ferromagnetic metals (G. Tatara, H. Fukuyama). Coulomb blockade and enhancement of magnetoresistance change in ultrasmall ferromagnetic double tunnel junctions (R. Kitawaki, F. Wakaya, S. Iwabuchi). Anomalous giant Barkhausen jumps in III-V-based diluted magnetic semiconductor (In, Mn) As at low temperatures (A. Oiwa et al.). Quantum depinning of a domain wall (G.-H. Kim).

**Quantum Transport.**Quantum dephasing in mesoscopic systems (Y. Imry). Decoherence in mesoscopic systems (R.A. Webb et al.). Quantum eraser and quantum Zeno effect in mesoscopic physics (G. Hackenbroich, B. Rosenow, H.A. Weidenmüller). New "coherent" bilayer quantum Hall states (A. Sawada et al.). Electron-electron scattering in two-dimensional electron gas under spatially modulated magnetic field (M. Kato et al.). Low-energy transport through a 1D Mott-Hubbard insulator (V.V. Ponomarenko, N. Nagaosa).

**Superconductors and Single Electronics.**Quantum coherence and decoherence in a superconducting single-electron transistor (Y. Nakamura, J.S. Tsai). Superconducting order parameters detected by single-electron transistors (S. Katsumoto, H. Sato, Y. Iye). Local detection of superconducting energy gap by small tunnel junctions (A. Kanda et al.). Vortex matter in high-Tc superconductor with columnar defects: a new field-driven coupling transition (T. Onogi et al.). Charging effects on superconducting proximity correction in normal-metal wire conductance (H. Nakano, H. Takayanagi). Andreev reflection at high magnetic fields (T.D. Moore, D.A. Williams). Towards an experiment of MQC: determination of the decoherence time from energy level quantization in rf SQUIDs (C. Cosmelli et al.).

**Nanoscale Physics and Atomics.**Property of atomic structures fabricated on the hydrogen-terminated Si(100) surface (T. Hashizume et al.). Coulomb blockade oscillation in single-atom nanotips (F. Yamaguchi et al.). Electronic structures of pseudo-one-dimensional dangling-bond structures fabricated on a hydrogen-terminated Si(100)2x1 surface (T. Hitosugi et al.). Nano-scale lithography using scanning probe microscopy (M. Ishibashi et al.).

**Mesoscopic Semicondutors and Normal Metals.**Chaos and quantum interference effect in semiconductor ballistic micro-structures (S. Kawabata). Thermodynamics and transport properties of a dissipative particle in a tight-binding mode (T. Kato, M. Imada). Spectral flow and gauge invariance of the effective field theory of charge density wave with topological defects (M. Hayashi). Decoherence and control of electrons on a metal surface (S. Ogawa, H. Nagano, H. Petek).

**Precise Measurements.**Disorder and the superfluid and ordering transitions in liquid helium (M.H.W. Chan). Superfluid interferometry: detection of absolute rotations and pinned vorticity (E. Varoquaux et al.). Real-time observation of dynamics of vortices in high-temperature superconductors by Lorentz microscopy (A. Tonomura et al.). Biprism interferences of He+-ions (F. Hasselbach, U. Maier). Neutron spin precessions on quasibound states through magnetic Fabry-Pé rot films in tunneling region (N. Achiwa et al.). Measurement of the transverse coherency of spin precessing neutron using multilayer spin splitters (M. Hino et al.). A delayed choice experiment using a multilayer cold neutron pulser (T. Kawai et al.). Complex systems and fundamental problems in quantum physics. Fluctuation-dissipation theorem and quantum decoherence (K. Fujikawa). Non-Hermitian quantum mechanics and localization in physical systems (N. Hatano). The double Stern-Gerlach experiment with multilayer cold neutron interferometry to test some quantum measurement theories (Y. Otake et al.). Quantum dynamical correlation of protons in water at T=298 K: new Raman light scattering and neutron Compton-scattering experiments (C.A. Chatzidimitriou-Dreismann, T. Abdul-Redah, R.M.F. Streffer). Evidence for anomalous correlations of protons in a metallic hydride (E.B. Karlsson et al.). The Wien filter as a tool to investigate the fundamentals of quantum mechanics (P. Sonnentag, F. Hasselbach). Decoherence of wavepackets under inelastic scattering (Y. Murayama, M. Honda). Time-dependent Bell's inequality in two neutral kaon systems (F. Uchiyama). Decoherence on discretized detectors (Z. Maki). List of participants. Author Index.