8,190 research outputs found
Scheme for teleportation of quantum states onto a mechanical resonator
We propose an experimentally feasible scheme to teleport an unkown quantum
state onto the vibrational degree of freedom of a macroscopic mirror. The
quantum channel between the two parties is established by exploiting radiation
pressure effects.Comment: 5 pages, 2 figures, in press on PR
Quantum State Reconstruction of a Bose-Einstein Condensate
We propose a tomographic scheme to reconstruct the quantum state of a
Bose-Einstein condensate, exploiting the radiation field as a probe and
considering the atomic internal degrees of freedom. The density matrix in the
number state basis can be directly retrieved from the atom counting
probabilities.Comment: 11 pages, LaTeX file, no figures, to appear in Europhysics Letter
Motional Squashed States
We show that by using a feedback loop it is possible to reduce the
fluctuations in one quadrature of the vibrational degree of freedom of a
trapped ion below the quantum limit. The stationary state is not a proper
squeezed state, but rather a ``squashed'' state, since the uncertainty in the
orthogonal quadrature, which is larger than the standard quantum limit, is
unaffected by the feedback action.Comment: 8 pages, 2 figures, to appear in the special Issue "Quantum
Correlations and Fluctuations" of J. Opt.
A Study of the Antiferromagnetic Phase in the Hubbard Model by means of the Composite Operator Method
We have investigated the antiferromagnetic phase of the 2D, the 3D and the
extended Hubbard models on a bipartite cubic lattice by means of the Composite
Operator Method within a two-pole approximation. This approach yields a fully
self-consistent treatment of the antiferromagnetic state that respects the
symmetry properties of both the model and the algebra. The complete phase
diagram, as regards the antiferromagnetic and the paramagnetic phases, has been
drawn. We firstly reported, within a pole approximation, three kinds of
transitions at half-filling: Mott-Hubbard, Mott-Heisenberg and Heisenberg. We
have also found a metal-insulator transition, driven by doping, within the
antiferromagnetic phase. This latter is restricted to a very small region near
half filling and has, in contrast to what has been found by similar approaches,
a finite critical Coulomb interaction as lower bound at half filling. Finally,
it is worth noting that our antiferromagnetic gap has two independent
components: one due to the antiferromagnetic correlations and another coming
from the Mott-Hubbard mechanism.Comment: 20 pages, 37 figures, RevTeX, submitted to Phys. Rev.
Spin and charge orderings in the atomic limit of the U-V-J model
In this paper we study a generalization of the 1D Hubbard model by
considering density-density and Ising-type spin-spin nearest neighbor (NN)
interactions, parameterized by and , respectively. We present the T=0
phase diagram for both ferro () and anti-ferro () coupling obtained
in the narrow-band limit by means of an extension to zero-temperature of the
transfer-matrix method. Based on the values of the Hamiltonian parameters, we
identify a number of phases that involve orderings of the double occupancy, NN
density and spin correlations, being these latter very fragile.Comment: 4 pages, 2 figures, SCES2011 Proceeding
Ponderomotive entangling of atomic motions
We propose the use of ponderomotive forces to entangle the motions of
different atoms. Two situations are analyzed: one where the atoms belong to the
same optical cavity and interact with the same radiation field mode; the other
where each atom is placed in own optical cavity and the output field of one
cavity enters the other.Comment: Revtex file, five pages, two eps figure
Exploring the Role of Problematic Social Network Site Use in the Link Between Reflective Functioning and Identity Processes in Adolescents
Literature highlighted that problematic social network site use might have relevant detrimental consequences on users’ well-being, particularly in adolescence. However, it is still not clear which variables could be considered protective or risk factors for such problematic use. The present study aimed to fill this gap, examining the relationship between reflective functioning and adolescents’ identity development, while taking problematic SNS use into account. A sample of 354 students (age range = 13–19; Mage = 16.18, SD = 1.58; 19.9% males) from two Italians high schools participated in the study. Results from structural equation modeling showed that adolescents with high levels of reflective functioning reported lower levels of problematic SNS use. Furthermore, problematic SNS use mediated the relationship between reflective functioning and identity development, by disfavouring identity in-depth exploration and favouring reconsideration of commitment. We discussed clinical and research implications
A Realistic Model to Support Rescue Operations after an Earthquake via UAVs
In this paper, we consider the problem of completely flying over an area just hit by an earthquake with a fleet of Unmanned Aerial Vehicles (UAVs) to opportunely direct rescue teams. The cooperation between UAVs ensures that the search for possible survivors can be faster and more effective than the solutions currently implemented by civil protection. To study this scenario, we introduce the Cover by Multitrips with Priorities (CMP) problem, which tries to keep into account all the main real-life issues connected to the flight and coordination of the UAVs. We conduct a theoretical study to estimate the best number of UAVs and additional batteries, to give indications to the organization that leads the rescue teams to be able to guarantee rapid and effective rescue. Finally, based on some theoretical considerations, we propose some heuristics that tackle the problem of flying over the whole area with a fleet of UAVs in the shortest possible time. Simulations show that they work efficiently in both the proposed scenarios and provide better performance than previous solutions once they are arranged to work in our scenarios. The main advantages of our approach w.r.t. the current drone-based solutions used by the civil defense are that UAVs do not need drivers so the time of all available rescue workers can be invested in doing something else. In our model, we take into account that some sites (e.g. buildings with a high fire risk or schools and hospitals) have a higher priority and must be inspected first, and the possibility that UAVs can make a decision based on what they detect. Finally, our approach allows UAVs to collaborate so that the same sites will be flown over exactly once in order to speed up the rescue mission
Pattern formation without heating in an evaporative convection experiment
We present an evaporation experiment in a single fluid layer. When latent
heat associated to the evaporation is large enough, the heat flow through the
free surface of the layer generates temperature gradients that can destabilize
the conductive motionless state giving rise to convective cellular structures
without any external heating. The sequence of convective patterns obtained here
without heating, is similar to that obtained in B\'enard-Marangoni convection.
This work present the sequence of spatial bifurcations as a function of the
layer depth. The transition between square to hexagonal pattern, known from
non-evaporative experiments, is obtained here with a similar change in
wavelength.Comment: Submitted to Europhysics Letter
Synthesis and characterization of entangled mesoscopic superpositions for a trapped electron
We propose a scheme for the generation and reconstruction of entangled states
between the internal and external (motional) degrees of freedom of a trapped
electron. Such states also exhibit quantum coherence at a mesoscopic level.Comment: 4 pages, 1 figure, RevTeX (twocolumn
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