1,358 research outputs found
Quantum Typicality and Initial Conditions
If the state of a quantum system is sampled out of a suitable ensemble, the
measurement of some observables will yield (almost) always the same result.
This leads us to the notion of quantum typicality: for some quantities the
initial conditions are immaterial. We discuss this problem in the framework of
Bose-Einstein condensates.Comment: 8 page
Long-lived entanglement of two multilevel atoms in a waveguide
We study the presence of nontrivial bound states of two multilevel quantum
emitters and the photons propagating in a linear waveguide. We characterize the
conditions for the existence of such states and determine their general
properties, focusing in particular on the entanglement between the two
emitters, that increases with the number of excitations. We discuss the
relevance of the results for entanglement preservation and generation by
spontaneous relaxation processes.Comment: 6 pages, 1 figur
Typical observables in a two-mode Bose system
A class of k-particle observables in a two-mode system of Bose particles is
characterized by typicality: if the state of the system is sampled out of a
suitable ensemble, an experimental measurement of that observable yields
(almost) always the same result. We investigate the general features of typical
observables, the criteria to determine typicality and finally focus on the case
of density correlation functions, which are related to spatial distribution of
particles and interference.Comment: 8 pages, 1 figur
Phase Transitions in Gauge Models: Towards Quantum Simulations of the Schwinger-Weyl QED
We study the ground-state properties of a class of lattice
gauge theories in 1 + 1 dimensions, in which the gauge fields are coupled to
spinless fermionic matter. These models, stemming from discrete representations
of the Weyl commutator for the group, preserve the unitary
character of the minimal coupling, and have therefore the property of formally
approximating lattice quantum electrodynamics in one spatial dimension in the
large- limit. The numerical study of such approximated theories is important
to determine their effectiveness in reproducing the main features and
phenomenology of the target theory, in view of implementations of cold-atom
quantum simulators of QED. In this paper we study the cases by
means of a DMRG code that exactly implements Gauss' law. We perform a careful
scaling analysis, and show that, in absence of a background field, all
models exhibit a phase transition which falls in the Ising
universality class, with spontaneous symmetry breaking of the symmetry. We
then perform the large- limit and find that the asymptotic values of the
critical parameters approach the ones obtained for the known phase transition
the zero-charge sector of the massive Schwinger model, which occurs at negative
mass.Comment: 15 pages, 18 figure
Tricriticalities and Quantum Phases in Spin-Orbit-Coupled Spin- Bose Gases
We study the zero-temperature phase diagram of a spin-orbit-coupled
Bose-Einstein condensate of spin , with equally weighted Rashba and
Dresselhaus couplings. Depending on the antiferromagnetic or ferromagnetic
nature of the interactions, we find three kinds of striped phases with
qualitatively different behaviors in the modulations of the density profiles.
Phase transitions to the zero-momentum and the plane-wave phases can be induced
in experiments by independently varying the Raman coupling strength and the
quadratic Zeeman field. The properties of these transitions are investigated in
detail, and the emergence of tricritical points, which are the direct
consequence of the spin-dependent interactions, is explicitly discussed.Comment: 6 pages, 2 figures + Supplemental Material. Revised version,
published in PR
Split and overlapped binary solitons in optical lattices
We analyze the energetic and dynamical properties of bright-bright (BB)
soliton pairs in a binary mixture of Bose-Einstein condensates subjected to the
action of a combined optical lattice, acting as an external potential for the
first species, while modulating the intraspecies coupling constant of the
second. In particular, we use a variational approach and direct numerical
integrations to investigate the existence and stability of BB solitons in which
the two species are either spatially separated (split soliton) or located at
the same optical lattice site (overlapped soliton). The dependence of these
solitons on the interspecies interaction parameter is explicitly investigated.
For repulsive interspecies interaction we show the existence of a series of
critical values at which transitions from an initially overlapped soliton to
split solitons occur. For attractive interspecies interaction only single
direct transitions from split to overlapped BB solitons are found. The
possibility to use split solitons for indirect measurements of scattering
lengths is also suggested.Comment: 9 pages, 10 figure
Discrete Abelian Gauge Theories for Quantum Simulations of QED
We study a lattice gauge theory in Wilson's Hamiltonian formalism. In view of
the realization of a quantum simulator for QED in one dimension, we introduce
an Abelian model with a discrete gauge symmetry , approximating
the theory for large . We analyze the role of the finiteness of the
gauge fields and the properties of physical states, that satisfy a generalized
Gauss's law. We finally discuss a possible implementation strategy, that
involves an effective dynamics in physical space.Comment: 13 pages, 3 figure
Unearthing wave-function renormalization effects in the time evolution of a Bose-Einstein condensate
We study the time evolution of a Bose-Einstein condensate in an accelerated
optical lattice. When the condensate has a narrow quasimomentum distribution
and the optical lattice is shallow, the survival probability in the ground band
exhibits a steplike structure. In this regime we establish a connection between
the wave-function renormalization parameter and the phenomenon of
resonantly enhanced tunneling.Comment: 12 pages, 3 figures. arXiv admin note: substantial text overlap with
arXiv:1201.628
Contagions
A hundred years separate two of the most successful masterpieces of English Gothic Fiction: The
Monk (1796) by Matthew Gregory Lewis and Dracula (1897) by Bram Stoker. The significance of
this circumstance goes beyond the mere chronological coincidence and is revealing of a close
connection linking the two texts. Such a connection, made up of a network of allusions, echoes,
anticipations and cross-references, derives from a specific set of narrative situations that The Monk
presents and Dracula redefines in order to reflect new and different axiologies.
These situations are centred on the motif of the Sleeping Beauty and its variations, a narrative topos
whose morbid connotations both novels emphasize in a typically Gothic manner. The analysis of
the ways in which Lewis and Stoker develop this motif sheds light on the dialectical relationship
connecting the two texts, and, with specific reference to Dracula, provides a new interpretative
perspective based on a metaliterary reading of Stoker’s novel, of the dark desires and evil pleasures
it evokes one hundred years after Lewis’s The Monk
Sipari gotici. Lo strano caso del Dr. Boaden e Mr. Lewis
Starting from the remarkable intellectual bond linking James Boaden and Matthew
Gregory Lewis, this paper investigates the nature of the relationship that, at the end
of the eighteenth century, came to be established between the theatrical adaptations
of the most popular Gothic novels and Gothic “original” plays. The fact that most authors
adapting Gothic novels for the theatre make a show of constructing a “gothicising”
kind of drama, conveying a certain cultural and social respectability, is interpreted
here as a deliberate attempt at defusing a genre, both narrative and theatrical, that was
perceived as subversive and anti-nationalistic. In this effort towards normalization, one
can see the reflections of a question of identity that runs through the society of the time
and that goes beyond the field of literature, even while involving it
- …