6,373 research outputs found
Genuine Tripartite Entanglement in a Spin-Star Network at Thermal Equilibrium
In a recent paper [M. Huber {\it et al}, Phys. Rev. Lett. {\bf 104}, 210501
(2010)] new criteria to find out the presence of multipartite entanglement have
been given. We exploit these tools in order to study thermal entanglement in a
spin-star network made of three peripheral spins interacting with a central
one. Genuine tripartite entanglement is found in a wide range of the relevant
parameters. A comparison between predictions based on the new criteria and on
the tripartite negativity is also given.Comment: 8 pages, 13 figure
Revealing non-classical behaviours in the oscillatory motion of a trapped ion
The possibility of revealing non-classical behaviours in the dynamics of a
trapped ion via measurements of the mean value of suitable operators is
reported. In particular we focus on the manifestation known as `` Parity
Effect\rq\rq which may be observed \emph{directly measuring} the expectation
value of an appropriate correlation operator. The experimental feasibility of
our proposal is discussed.Comment: 5 pages, 2 figure
Quantum Phase Transitions and Heat Capacity in a two-atoms Bose-Hubbard Model
We show that a two-atoms Bose-Hubbard model exhibits three different phases
in the behavior of thermal entanglement in its parameter space. These phases
are demonstrated to be traceable back to the existence of quantum phase
transitions in the same system. Significant similarities between the behaviors
of thermal entanglement and heat capacity in the parameter space are brought to
light thus allowing to interpret the occurrence and the meaning of all these
three phases.Comment: 6 pages, 3 figure
Geometric phase accumulation-based effects in the quantum dynamics of an anisotropically trapped ion
New physical effects in the dynamics of an ion confined in an anisotropic
two-dimensional Paul trap are reported. The link between the occurrence of such
manifestations and the accumulation of geometric phase stemming from the
intrinsic or controlled lack of symmetry in the trap is brought to light. The
possibility of observing in laboratory these anisotropy-based phenomena is
briefly discussed.Comment: 10 pages. Acta Physica Hungarica B 200
Zeno Dynamics and High-Temperature Master Equations Beyond Secular Approximation
Complete positivity of a class of maps generated by master equations derived
beyond the secular approximation is discussed. The connection between such
class of evolutions and physical properties of the system is analyzed in depth.
It is also shown that under suitable hypotheses a Zeno dynamics can be induced
because of the high temperature of the bath.Comment: 9 pages, 2 figure
Heat Capacity and Entanglement Measure in a simple two-qubit model
A simple two-qubit model showing Quantum Phase Transitions as a consequence
of ground state level crossings is studied in detail. Using the Concurrence of
the system as an entanglement measure and heat capacity as a marker of
thermodynamical properties, an analytical expression giving the latter in terms
of the former is obtained. A protocol allowing an experimental measure of
entanglement is then presented and compared with a related proposal recently
reported by Wie\'sniak, Vedral and BruknerComment: 7 pages, 3 figure
Entropy production and information fluctuations along quantum trajectories
Employing the stochastic wave function method, we study quantum features of
stochastic entropy production in nonequilibrium processes of open systems. It
is demonstarted that continuous measurements on the environment introduce an
additional, non-thermal contribution to the entropy flux, which is shown to be
a direct consequence of quantum fluctuations. These features lead to a quantum
definition of single trajectory entropy contributions, which accounts for the
difference between classical and quantum trajectories and results in a quantum
correction to the standard form of the integral fluctuation theorem.Comment: 9 pages, 5 figure
Dynamics of a particle confined in a two-dimensional dilating and deforming domain
Some recent results concerning a particle confined in a one-dimensional box
with moving walls are briefly reviewed. By exploiting the same techniques used
for the 1D problem, we investigate the behavior of a quantum particle confined
in a two-dimensional box (a 2D billiard) whose walls are moving, by recasting
the relevant mathematical problem with moving boundaries in the form of a
problem with fixed boundaries and time-dependent Hamiltonian. Changes of the
shape of the box are shown to be important, as it clearly emerges from the
comparison between the "pantographic", case (same shape of the box through all
the process) and the case with deformation.Comment: 13 pages, 2 figure
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