IF - Artigos publicados em periódicoshttp://repositorio.bc.ufg.br//handle/ri/13592024-09-12T18:29:29Z2024-09-12T18:29:29Z7321Teleportation of a weak coherent cavity field statehttp://repositorio.bc.ufg.br//handle/ri/248782024-07-15T12:44:03Z2016-01-01T00:00:00Zdc.title: Teleportation of a weak coherent cavity field state
dc.description.abstract: In this paper we propose a scheme to teleport a weak coherent cavity field state. The scheme relies on the resonant atom-field interaction inside a high-Q cavity. The mean photon-number of the cavity field is assumed much smaller than one, hence the field decay inside the cavity can be effectively suppressed.
2016-01-01T00:00:00ZModulation of localized solutions in an inhomogeneous saturable nonlinear Schrödinger equationhttp://repositorio.bc.ufg.br//handle/ri/248772024-07-15T12:41:27Z2017-01-01T00:00:00Zdc.title: Modulation of localized solutions in an inhomogeneous saturable nonlinear Schrödinger equation
dc.description.abstract: In this paper we study the modulation of localized solutions by an inhomogeneous saturable nonlinear medium. Throughout an appropriate ansatz we convert the inhomogeneous saturable nonlinear Schrödinger equation in a homogeneous one. Then, via a variational approach we construct localized solutions of the autonomous equation and we present some modulation patterns of this localized structures. We have checked the stability of such solutions through numerically simulations.
2017-01-01T00:00:00ZZero-dimensional limit of the two-dimensional Lugiato-Lefever equationhttp://repositorio.bc.ufg.br//handle/ri/248762024-07-15T12:39:16Z2017-01-01T00:00:00Zdc.title: Zero-dimensional limit of the two-dimensional Lugiato-Lefever equation
dc.description.abstract: We study effects of tight harmonic-oscillator confinement on the electromagnetic field in a laser cavity by solving the two-dimensional Lugiato-Lefever (2D LL) equation, taking into account self-focusing or defocusing nonlinearity, losses, pump, and the trapping potential. Tightly confined (quasi-zero-dimensional) optical modes (pixels), produced by this model, are analyzed by means of the variational approximation, which provides a qualitative picture of the ensuing phenomena. This is followed by systematic simulations of the time-dependent 2D LL equation, which reveal the shape, stability, and dynamical behavior of the resulting localized patterns. In this way, we produce stability diagrams for the expected pixels. Then, we consider the LL model with the vortical pump, showing that it can produce stable pixels with embedded vorticity (vortex solitons) in remarkably broad stability areas. Alongside confined vortices with the simple single-ring structure, in the latter case the LL model gives rise to stable multi-ring states, with a spiral phase field. In addition to the numerical results, a qualitatively correct description of the vortex solitons is provided by the Thomas-Fermi approximation.
2017-01-01T00:00:00ZQuasi-one-dimensional approximation for Bose–Einstein condensates transversely trapped by a funnel potentialhttp://repositorio.bc.ufg.br//handle/ri/248752024-07-15T12:32:24Z2019-01-01T00:00:00Zdc.title: Quasi-one-dimensional approximation for Bose–Einstein condensates transversely trapped by a funnel potential
dc.description.abstract: Starting from the standard three-dimensional (3D) Gross–Pitaevskii equation (GPE) and using a variational approximation, we derive an effective one-dimensional nonpolynomial Schrödinger equation (1D-NPSE) governing the axial dynamics of atomic Bose–Einstein condensates (BECs) under the action of a singular but physically relevant funnel-shaped transverse trap, i.e. an attractive 2D potential ∼−1/r (where r is the radial coordinate in the transverse plane), in combination with the repulsive self-interaction. Wave functions of the trapped BEC are regular, in spite of the potential's singularity. The model applies to a condensate of particles (small molecules) carrying a permanent electric dipole moment in the field of a uniformly charged axial thread, as well as to a quantum gas of magnetic atoms pulled by an axial electric current. By means of numerical simulations, we verify that the effective 1D-NPSE provides accurate static and dynamical results, in comparison to the full 3D GPE, for both repulsive and attractive signs of the intrinsic nonlinearity.
2019-01-01T00:00:00ZAnderson localization induced by interaction in linearly coupled binary Bose-Einstein condensateshttp://repositorio.bc.ufg.br//handle/ri/248742024-07-15T12:28:42Z2021-01-01T00:00:00Zdc.title: Anderson localization induced by interaction in linearly coupled binary Bose-Einstein condensates
dc.description.abstract: In this paper we investigate the existence of Anderson localization induced by one specific component of a binary Bose-Einstein condensate (BEC). We use a mean-field approach, in which each type of particle of the BEC is considered as a specific field, and we consider that only one kind of particle is subject to a quasiperiodic potential, which induces a localization in the partner field. We assume the system is under a Rabi coupling, i.e., a linear coupling mixing the two-field component, and we investigate the conditions associated with the parameter values of the system for observing the localization. Numerical simulations are performed, confirming the existence of Anderson localization in the partner field.
2021-01-01T00:00:00ZParametrically driven localized magnetic excitations with spatial inhomogeneityhttp://repositorio.bc.ufg.br//handle/ri/248732024-07-15T12:27:02Z2019-01-01T00:00:00Zdc.title: Parametrically driven localized magnetic excitations with spatial inhomogeneity
dc.description.abstract: In this paper we study an inhomogeneous ferromagnet with uniaxial anisotropy and applied magnetic field via the magnetic field component of the propagating electromagnetic wave in the medium. It is observed that the magnetic excitations are governed by localized solutions and the corresponding electromagnetic wave is modulated in the form of soliton modes driven by the inhomogeneity. The localized solutions are obtained in an analytical way by employing a variational approach. The effect of different types of magnetic inhomogeneity is studied for three different types of ansätze. Interestingly, the regions of validity of each ansatz are slightly different, demonstrating that both may be interesting for understanding the whole system.
2019-01-01T00:00:00ZLocalization of optical pulses in guided wave structures with only fourth order dispersionhttp://repositorio.bc.ufg.br//handle/ri/248722024-07-15T12:24:47Z2019-01-01T00:00:00Zdc.title: Localization of optical pulses in guided wave structures with only fourth order dispersion
dc.description.abstract: Inspired by the recent realization of pure-quartic solitons (Blanco-Redondo et al. (2016) [1]), in the present work we study the localization of optical pulses in a similar system, i.e., a silicon photonic crystal air-suspended structure with a hexagonal lattice. The propagation of ultrashort pulses in such a system is well described by a generalized nonlinear Schrödinger (NLS) equation, which in certain conditions works with near-zero group-velocity dispersion and third order dispersion. In this case, the NLS equation has only the fourth order dispersion term. In the present model, we introduce a quasiperiodic linear coefficient that is responsible to induce the localization. The existence of Anderson localization has been confirmed by numerical simulations even when the system presents a small defocusing nonlinearity.
2019-01-01T00:00:00ZAn effective equation for quasi-one-dimensional funnel-shaped Bose–Einstein condensates with embedded vorticityhttp://repositorio.bc.ufg.br//handle/ri/248712024-07-15T12:22:29Z2022-01-01T00:00:00Zdc.title: An effective equation for quasi-one-dimensional funnel-shaped Bose–Einstein condensates with embedded vorticity
dc.description.abstract: On the basis of a recently introduced model for the Bose–Einstein condensate (BEC) trapped
in the 2D “funnel” potential, ∼ −r−1, we develop analysis for vortex modes, which are confined in the
transverse direction by the self-attraction, or by the trapping potential, in the case of self-repulsion. Linear
3D wave functions are found exactly for eigenstates with an orbital momentum. In the case of self-repulsion,
3D wave functions are obtained by means of the Thomas–Fermi approximation. Then, with the help
of the variational method, the underlying Gross–Pitaevskii equation is reduced to a 1D nonpolynomial
Schr¨odinger equation (NPSE) for modes with zero or nonzero embedded vorticity, which are tightly confined
by the funnel potential in the transverse plane. Numerical results demonstrate high accuracy of the NPSE
reduction for both signs of the nonlinearity. The analysis is performed for stationary modes and for traveling
ones colliding with a potential barrier. By means of simulations of NPSE with the self-attraction, collisions
between solitons are studied too, demonstrating elastic and inelastic outcomes, depending on the impact
velocity and underlying vorticity. A boundary of the stability of 3D vortices with winding number S = 1
against spontaneous splitting in two fragments is identified in the case of the self-attraction, all vortices
with S ≥ 2 being unstable.
2022-01-01T00:00:00ZEffective equation for quasi-one dimensional tube-shaped Bose–Einstein condensateshttp://repositorio.bc.ufg.br//handle/ri/248702024-07-15T12:20:07Z2019-01-01T00:00:00Zdc.title: Effective equation for quasi-one dimensional tube-shaped Bose–Einstein condensates
dc.description.abstract: In this letter we derive an effective 1D equation that describes the axial dynamics of a tube-shaped Bose–Einstein condensate. The dimensional reduction is achieved by using a variational approach starting from the 3D Gross–Pitaevskii equation (GPE) in presence of a nonharmonic external potential in the transverse direction and generic in the axial one. The resulting equation is a time-dependent 1D nonpolynomial Schrödinger equation (NPSE). In view to check the accuracy of our 1D-NPSE, we numerically investigated the ground state properties of such a system that are in perfect agreement with the results produced by the 3D-GPE. We also compare the results with those from an 1D cubic nonlinear Schrödinger equation and the Thomas–Fermi approximation. Finally, the dynamics of ground states obtained from our 1D-NPSE is verified numerically by considering a small change in the strength of the axial confining potential.
2019-01-01T00:00:00ZDouble-layer Bose-Einstein condensates: a quantum phase transition in the transverse direction, and reduction to two dimensionshttp://repositorio.bc.ufg.br//handle/ri/248692024-07-15T12:18:00Z2020-01-01T00:00:00Zdc.title: Double-layer Bose-Einstein condensates: a quantum phase transition in the transverse direction, and reduction to two dimensions
dc.description.abstract: We revisit the problem of the reduction of the three-dimensional (3D) dynamics of Bose-Einstein condensates, under the action of strong confinement in one direction (𝑧), to a 2D mean-field equation. We address this problem for the confining potential with a singular term, viz., 𝑉𝑧(𝑧)=2𝑧2+𝜁2/𝑧2, with constant 𝜁. A quantum phase transition is induced by the latter term, between the ground state (GS) of the harmonic oscillator and the 3D condensate split in two parallel noninteracting layers, which is a manifestation of the “superselection” effect. A realization of the respective physical setting is proposed, making use of resonant coupling to an optical field, with the resonance detuning modulated along 𝑧. The reduction of the full 3D Gross-Pitaevskii equation (GPE) to the 2D nonpolynomial Schrödinger equation (NPSE) is based on the factorized ansatz, with the 𝑧 -dependent multiplier represented by an exact GS solution of the 1D Schrödinger equation with potential 𝑉𝑧(𝑧). For both repulsive and attractive signs of the nonlinearity, the 2D NPSE produces GS and vortex states, that are virtually indistinguishable from the respective numerical solutions provided by full 3D GPE. In the case of the self-attraction, the threshold for the onset of the collapse, predicted by the 2D NPSE, is also virtually identical to its counterpart obtained from the 3D equation. In the same case, stability and instability of vortices with topological charge 𝑆=1, 2, and 3 are considered in detail. Thus, the procedure of the spatial-dimension reduction, 3D → 2D, produces very accurate results, and it may be used in other settings.
2020-01-01T00:00:00Z