846 research outputs found
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
Damped harmonic oscillators in the holomorphic representation
Quantum dynamical semigroups are applied to the study of the time evolution
of harmonic oscillators, both bosonic and fermionic. Explicit expressions for
the density matrices describing the states of these systems are derived using
the holomorphic representation. Bosonic and fermionic degrees of freedom are
then put together to form a supersymmetric oscillator; the conditions that
assure supersymmetry invariance of the corresponding dynamical equations are
explicitly derived.Comment: 19 pages, plain-TeX, 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
Comprehensive Pain Management Using Opioids for Children and Adolescents: Still a Wild Goose to Chase?
Children and adolescents treated for acute and chronic pain represent particular vulnerable patients with distinct and unmet medical and psychosocial needs that continue even beyond the complexity of treating the diseases they suffer [...
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
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
Dissipative neutrino oscillations in randomly fluctuating matter
The generalized dynamics describing the propagation of neutrinos in randomly
fluctuating media is analyzed: it takes into account matter-induced,
decoherence phenomena that go beyond the standard MSW effect. A widely adopted
density fluctuation pattern is found to be physically untenable: a more general
model needs to be instead considered, leading to flavor changing effective
neutrino-matter interactions. They induce new, dissipative effects that modify
the neutrino oscillation pattern in a way amenable to a direct experimental
analysis.Comment: 14 pages, plain-Te
Relaxation to equilibrium driven via indirect control in Markovian dynamics
We characterize to what extent it is possible to modify the stationary states
of a quantum dynamical semigroup, that describes the irreversible evolution of
a two-level system, by means of an auxiliary two-level system. We consider
systems that can be initially entangled or uncorrelated. We find that the
indirect control of the stationary states is possible, even if there are not
initial correlations, under suitable conditions on the dynamical parameters
characterizing the evolution of the joint system.Comment: revtex4, 7 page
On the Additivity of Entanglement of Formation
We study whether the entanglement of formation is additive over tensor
products and derive a necessary and sufficient condition for optimality of
vector states that enables us to show additivity in two special cases.Comment: 4 pages, Latex, doublecolum
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 , and , admitting that the quantum decoherence parameter is related
to the neutrino energy as : ,
with 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
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