583 research outputs found
Neutral kaons in random media
The generalized dynamics describing the propagation of neutral kaons in
randomly fluctuating media is derived and analyzed. It takes into account
possible matter-induced effects leading to loss of phase coherence and
dissipation. The study of selected neutral kaon observables indicates that
these non-standard effects are amenable to a direct experimental analysis.Comment: 21 pages, plain-TeX, corrected typ
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
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
Entangling oscillators through environment noise
We consider two independent bosonic oscillators immersed in a common bath,
evolving in time with a completely positive, markovian, quasi-free (Gaussian)
reduced dynamics. We show that an initially separated Gaussian state can become
entangled as a result of a purely noisy mechanism. In certain cases, the
dissipative dynamics allows the persistence of these bath induced quantum
correlations even in the asymptotic equilibrium state.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
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
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
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
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