322 research outputs found
Anderson localization in the quintic nonlinear Schr\"odinger equation
In the present paper we consider the quintic defocusing nonlinear
Schr\"odinger equation in presence of a disordered random potential and we
analyze the effects of the quintic nonlinearity on the Anderson localization of
the solution. The main result shows that Anderson localization requires a
cutoff on the value of the parameter which controls the quintic nonlinearity,
with the cutoff depending on the amplitude of the random potential.Comment: 4 pages, 7 figure
A new view on spin reduced density matrix for relativistic particles
We present a new interpretation for reduced density matrices of secondary
variables in relativistic systems via an analysis of Wigner's method to
construct the irreducible unitary representations of the Poincar\'e group. We
argue that the usual partial trace method used to obtain spin reduced matrices
is not fully rigorous, however, employing our interpretation, similar effective
reduced density matrices can be constructed. In addition, we show that our
proposal is more useful than the usual one since we are not restricted only to
the reduced density matrices that could be obtained by the ordinary partial
trace method
Unidimensional reduction of the 3D Gross-Pitaevskii equation with two- and three-body interactions
We deal with the three-dimensional Gross-Pitaevskii equation, which is used
to describe a cloud of dilute bosonic atoms that interact under competing two-
and three-body scattering potentials. We study the case where the cloud of
atoms is strongly confined in two spatial dimensions, allowing us to build an
unidimensional nonlinear equation, controlled by the nonlinearities and the
confining potentials that trap the system along the longitudinal coordinate. We
focus attention on specific limits, dictated by the cubic and quintic
coefficients, and we implement numerical simulations to help us to quantify the
validity of the procedure.Comment: 6 pages, 4 figures; version to appear in PR
Modulation of breathers in cigar-shaped Bose-Einstein condensates
We present new solutions to the nonautonomous nonlinear Schroedinger equation
that may be realized through convenient manipulation of Bose-Einstein
condensates. The procedure is based on the modulation of breathers through an
analytical study of the one-dimensional Gross-Pitaevskii equation, which is
known to offer a good theoretical model to describe quasi-one-dimensional
cigar-shaped condensates. Using a specific Ansatz, we transform the
nonautonomous nonlinear equation into an autonomous one, which engenders
composed states corresponding to solutions localized in space, with an
oscillating behavior in time. Numerical simulations confirm stability of the
breathers against random perturbation on the input profile of the solutions
Systematic Construction of Genuine Multipartite Entanglement Criteria using Uncertainty Relations
A general procedure to construct criteria for identifying genuine
multipartite continuous variable entanglement is presented. It relies on the
proper definition of adequate global operators describing the multipartite
system, the positive partial transpose criterion of separability, and quantum
mechanical uncertainty relations. As a consequence, each criterion encountered
consists of a single inequality that is nicely computable and experimentally
feasible, and that when violated is sufficient condition for genuine
multipartite entanglement. Additionally we show that the previous work of van
Loock and Furusawa [Phys. Rev. A, 67, 052315 (2003)] is a special case of our
result that includes strongest criteria to detect entanglement.Comment: 15 pages, 2 tables and 1 figur
Nonclassical degree of states of single and bipartite systems
We consider experimental routes to determine the nonclassical degree of
states of a field mode. We adopt a distance-type criterium based on the
Hilbert-Schmidt metric to quantify the nonclassicality. The concept of
nonclassical degree is extended for states of bipartite systems, allowing us to
discuss a possible connection between nonclassicality and entanglement
measures.Comment: 10 pages, 1 figur
A proposal to implement a quantum delayed choice experiment assisted by a cavity QED
We propose a scheme feasible with current technology to implement a quantum
delayed-choice experiment in the realm of cavity QED. Our scheme uses two-level
atoms interacting on and off resonantly with a single mode of a high Q cavity.
At the end of the protocol, the state of the cavity returns to its ground
state, allowing new sequential operations. The particle and wave behavior,
which are verified in a single experimental setup, are postselected after the
atomic states are selectively detected.Comment: 3 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1208.0802 by other author
Generation of arbitrary Fock states via resonant interactions in cavity QED
We propose a scheme to generate arbitrary Fock states |N> in a cavity QED
using N resonant Rydberg atoms. The atom-field interaction times are controlled
via Stark-shifts adjusted in a way that each atom transfers a photon to the
cavity, turning atomic detections useless. Fluctuations affecting the control
of the atom-field interactions are also considered.Comment: 3 pages, 2 figures
Bright solitons from the nonpolynomial Schr\"odinger equation with inhomogeneous defocusing nonlinearities
Extending the recent work on models with spatially nonuniform nonlinearities,
we study bright solitons generated by the nonpolynomial self-defocusing (SDF)
nonlinearity in the framework of the one-dimensional (1D) Mu\~{n}oz-Mateo -
Delgado (MM-D) equation (the 1D reduction of the Gross-Pitaevskii equation with
the SDF nonlinearity), with the local strength of the nonlinearity growing at
any rate faster than |x| at large values of coordinate x. We produce numerical
solutions and analytical ones, obtained by means of the Thomas-Fermi
approximation (TFA), for nodeless ground states, and for excited modes with 1,
2, 3, and 4 nodes, in two versions of the model, with the steep (exponential)
and mild (algebraic) nonlinear-modulation profiles. In both cases, the ground
states and the single-node ones are completely stable, while the stability of
the higher-order modes depends on their norm (in the case of the algebraic
modulation, they are fully unstable). Unstable states spontaneously evolve into
their stable lower-order counterparts.Comment: 5 pages, 6 figures, (Physical Review E, in press
Splitting of quantum information in traveling wave fields using only linear optical elements
In this brief report we present a feasible scheme to split quantum
information in the realm of traveling waves. An oversimplified scheme is also
proposed for the generation of a class of W states useful for perfect
teleportation and superdense coding. The scheme employs only linear optical
elements as beam splitters and phase shifters, in addition to photon counters
and one-photon sources. It is shown that splitting of quantum information with
high fidelity is possible even including inefficiency of the detectors and
photoabsorption of the beam splitters.Comment: 4 pages, 6 figure
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