Decoherence, Entanglement and Information Protection in Complex Quantum Systems : Proceedings of the NATO ARW on Decoherence, Entanglement and Information Protection in Complex Quantum Systems, Les Houches, France, from 26 to 30 April 2004.

Dynamics of an open system interacting with theenvironment considered as a thermostate may be formulatedin terms of a master equation with an integral operator allowing for the relaxation process, [Zwanzig 1960]. In some part- ular cases this operator hasashort-lastingkernel that enables one to consider therelaxation as a Markovian process and to obtainthe master equation inthe Lindblad form, [Lindblad 1976 (a)]. In some situations the memory effects become, however, important and the dynamics of thesystem gets much more involved, [Barnett 2001]. A similar situation arises inthe case where a set of consecutive or continuous measurements is performed. The purpose of this article is to consider a situation where some simplification of the generalform of the master equation with memory isstill possibleand the result isasimpler master equation. In particular, we consider the case of a dynamic system c- pled to a measured ancilla via a nondemolition interaction, [Caves 1980]. This simplifies the consideration essentiallywhereas providing an important special case inwhich the energy of the dynamic part is conserved. We consider a composite quantum system consisting of a dynamic part - teracting with an ancillary part, the latter being subject to repeated projective measurements. The entire quantum system is assumed to evolve unitarily d- ing time ? t between the measurements. As a specific example, we analyze a harmonic oscillator coupledtoatwo-level ancillathat issubject to measu- ments.

Acknowledgments,Editorial article; V. M. Akulin et al. Part I Role of entanglement in quantum computing and information processing. Quantum ensembles and quantum informatics ; V. M. Akuli et al.,Entanglement in quantum information processing ; S. L. Braunstein. ,Easy control over fermionic computations;Y. Ozhigov.. Part II Multiatom and multiphoton entanglement. Multiatom and multiphoton entanglement; D. Petrosya et al.,On the advanced wave model of parametric down-conversion; A. I. Lvovsky and T. Aichele. .Quantum logics based on four-photon entanglement; Ph. Walther and A. Zeilinger. Towards quantum control of light; L. I. Childress et al. Deterministic entanglement of single photons; D. Petrosyan. Selective control of high-order atomic coherences; Yu. P. Malakyan et al. Strong entanglement of bright light beams in controlled quantum systems; G. Yu. Kryuchkyan and H. H. Adamyan. Part III Adiabatic and nonadiabatic protection from Decoherence. Adiabatic and nonadiabatic protection from decoherence; S. Pellegrin et al. Coherence protection by the quantum Zeno effect; E. Brion et al. Implementation of protected qubits by Josephson junction arrays; L. B. Ioffe. Coherence protection near energy gaps; C. Mewes et al. Zeno and anti-Zeno dynamics; G. Kurizki et al. Part IV Non-Markovian decay and decoherence in open quantum systems. Non-Markovian decay and decoherence in open quantum systems; J. Salo et al. The varieties of Master Equations; J. Salo et al. Quantum dynamics effected by repeated measurements; J. Clausen et al. Motional damping of impurity atoms in Bose-Einstein condensates; I. E. Mazets and G. Kurizki. Part V Internal-translational entanglement and interference in atoms and molecules. Internal-translational entanglement and interference in atoms and molecules; T. Opatrn et al. Atom-mesoscopic field entanglement S. Haroch et al. Coherence and decoherence experiments with fullerenes, M. Arnd et al. Distant entanglement of macroscopic gassamples; J. Sherson et al. Entanglement in optical lattices; T. Opatrn et al. Investigation of Autler-Townes effect in sodium dimmers; R. Garcia-Fernande et al. Transition steering via space-dependent coupling; M. Leibscher and S. Stenholm.Coherence and decoherence in Rydberg gases; P. Pillet et al. Part VI Proton entanglement and decoherence in solids. Schrödinger’s cat states of protons in condensed matter; M. Krzystynia et al. Anomalous neutron inelastic cross sections at eV energy transfers; J. Mayers and T. Abdul-Redah. Quantum entanglement and decoherence due to electrons-protons coupling; T. Abdul-Redah et al. Attosecond effects in scattering of neutrons and electrons from protons; C. A. Chatzidimitriou-Dreismann et al. Macroscopic quantum entanglement; F. Fillaux. Probing short-lived entanglement with inelastic X-ray scattering; H. Nauman et al. Proton-proton correlations in condensed matter; E. B. Karlsson. Is Fermi’s golden rule always true for Compton scattering?; I. E. Mazet et al. On correlation approach to scattering in the decoherence timescale; C. A. Chatzidimitriou-Dreismann and S. Stenholm. Part VII Coherence and entanglement in mesoscopic systems. Coherence and entanglement in mesoscopic systems; M. Blaauboer et al. Probe scattering by fluctuating multiatom ensembles in optical lattices; M. Blaauboer et al. Bose-Einstein condensates with laser-induced dipole-dipole interactions; D. O’Dell et al.Atom optics with Bose-Einstein condensation using optical potentials; N. Katz et al. A mesoscopic Mach-Zehnder interferometer; Y. Ji et al. Coherent transport by adiabatic pumping; M. Blaauboer. Zeno and anti-Zeno effects in driven josephson junctions; A. Barone et al. Fabrication of 'quiet' superconducting flux-qubits; E. Sarnelli et al.Broken symmetry and coherence; A. M. Dykhne and A. G. Rudavets. References , Index