Asymptotic Entanglement and Lindblad Dynamics: a Perturbative Approach

We consider an open bipartite quantum system with dissipative Lindblad type dynamics. In order to study the entanglement of the stationary states, we develop a perturbative approach and apply it to the physically significant case when a purely dissipative perturbation is added to the unperturbed generator which by itself would produce reversible unitary dynamics.Comment: 15 page

Open Quantum Dynamics: Complete Positivity and Entanglement

We review the standard treatment of open quantum systems in relation to quantum entanglement, analyzing, in particular, the behaviour of bipartite systems immersed in a same environment. We first focus upon the notion of complete positivity, a physically motivated algebraic constraint on the quantum dynamics, in relation to quantum entanglement, i.e. the existence of statistical correlations which can not be accounted for by classical probability. We then study the entanglement power of heat baths versus their decohering properties, a topic of increasing importance in the framework of the fast developing fields of quantum information, communication and computation. The presentation is self contained and, through several examples, it offers a detailed survey of the physics and of the most relevant and used techniques relative to both quantum open system dynamics and quantum entanglement.Comment: LaTex, 77 page

Planck's scale dissipative effects in atom interferometry

Atom interferometers can be used to study phenomena leading to irreversibility and dissipation, induced by the dynamics of fundamental objects (strings and branes) at a large mass scale. Using an effective, but physically consistent description in terms of a master equation of Lindblad form, the modifications of the interferometric pattern induced by the new phenomena are analyzed in detail. We find that present experimental devices can in principle provide stringent bounds on the new effects.Comment: 12 pages, plain-Te

Joint reality and Bell inequalities for consecutive measurements

Some new Bell inequalities for consecutive measurements are deduced under joint realism assumption, using some perfect correlation property. No locality condition is needed. When the measured system is a macroscopic system, joint realism assumption substitutes the non-invasive hypothesis advantageously, provided that the system satisfies the perfect correlation property. The new inequalities are violated quantically. This violation can be expected to be more severe than in the case of precedent temporal Bell inequalities. Some microscopic and mesoscopic situations, in which the new inequalities could be tested, are roughly considered.Comment: 7 pages, no figure

Dissipation and decoherence in photon interferometry

The propagation of polarized photons in optical media can be effectively modeled by means of quantum dynamical semigroups. These generalized time evolutions consistently describe phenomena leading to loss of phase coherence and dissipation originating from the interaction with a large, external environment. High sensitive experiments in the laboratory can provide stringent bounds on the fundamental energy scale that characterizes these non-standard effects.Comment: 14 pages, plain-Te

Effective dissipative dynamics for polarized photons

In the framework of open quantum systems, the propagation of polarized photons can be effectively described using quantum dynamical semigroups. These extended time-evolutions induce irreversibility and dissipation. Planned, high sensitive experiments, both in the laboratory and in space, will be able to put stringent bounds on these non-standard effects.Comment: 15 pages, plain-TeX, no figure

Probing possible decoherence effects in atmospheric neutrino oscillations

It is shown that the results of the Super-Kamiokande atmospheric neutrino experiment, interpreted in terms of nu_munu_tau flavor transitions, can probe possible decoherence effects induced by new physics (e.g., by quantum gravity) with high sensitivity, supplementing current laboratory tests based on kaon oscillations and on neutron interferometry. By varying the (unknown) energy dependence of such effects, one can either obtain strong limits on their amplitude, or use them to find an unconventional solution to the atmospheric nu anomaly based solely on decoherence.Comment: Title changed; major changes in the text; includes the discussion of a new solution to the atmosheric neutrino anomaly, based on decoherence; a second figure and a note have been adde

Quantum Dissipative Effects and Neutrinos : current constraints and future perspectives

We establish the most stringent experimental constraints coming from recent terrestrial neutrino experiments on quantum mechanical decoherence effects in neutrino systems. Taking a completely phenomenological approach, we probe vacuum oscillations plus quantum decoherence between two neutrino species in the channels $\nu_\mu \to \nu_\tau$, $\nu_\mu \to \nu_e$ and $\nu_e \to \nu_\tau$, admitting that the quantum decoherence parameter $\gamma$ is related to the neutrino energy $E_\nu$ as : $\gamma=\gamma_0 (E_\nu/\text{GeV})^{n}$, with $n=-1,0,1$ and 2. Our bounds are valid for a neutrino mass squared difference compatible with the atmospheric, the solar and, in many cases, the LSND scale. We also qualitatively discuss the perspectives of the future long baseline neutrino experiments to further probe quantum dissipation.Comment: 26 pages, 8 encapsulated postscript figure

Information-theoretical meaning of quantum dynamical entropy

The theory of noncommutative dynamical entropy and quantum symbolic dynamics for quantum dynamical systems is analised from the point of view of quantum information theory. Using a general quantum dynamical system as a communication channel one can define different classical capacities depending on the character of resources applied for encoding and decoding procedures and on the type of information sources. It is shown that for Bernoulli sources the entanglement-assisted classical capacity, which is the largest one, is bounded from above by the quantum dynamical entropy defined in terms of operational partitions of unity. Stronger results are proved for the particular class of quantum dynamical systems -- quantum Bernoulli shifts. Different classical capacities are exactly computed and the entanglement-assisted one is equal to the dynamical entropy in this case.Comment: 6 page

Environment Induced Entanglement in Markovian Dissipative Dynamics

We show that two, non interacting 2-level systems, immersed in a common bath, can become mutually entangled when evolving according to a Markovian, completely positive reduced dynamics.Comment: 4 pages, LaTex, no figures, added reference