2019, Articolo in rivista, ENG
Pitaevskii, Lev P.
Solitons, that is stable localized perturbations of a medium, are the topological excitations of nonlinear systems. They can be stable and live for a long time and may have promising applications for telecommunication. The basic one is the Tsuzuki dark soliton, which can be described by an analytical solution of the Gross-Pitaevskii equation (GPE). Ultracold Bose-Einstein condensed (BEC) gases are an important example for the investigation of solitons which can be created by phase and density imprinting. New possibilities arise in mixtures of different hyperspin states of ultra-cold gases, where the so-called magnetic solitons (MS), that is localized magnetized regions, can exist. We will see that these MS permit an analytical description. New peculiar phenomena can take place in the presence of a coherent Rabi coupling between the spin states, where two different type of solitons existso-called 2 and 0 solitons. 2 solitons, unlike the usual Tsuzuki solitons, have at small velocity a positive effective mass and consequently do not undergo the snake instability. Solitary waves can oscillate in BEC gases along elongated traps. The theoretical description of this motion requires the knowledge of the effective soliton mass and the effective number of particles in the soliton. These quantities are calculated.
2018, Articolo in rivista, ENG
Villari L.D.M.; Faccio D.; Biancalana F.; Conti C.
Quantum evaporation may occur in a variety of systems such as superfluids, Bose-Einstein condensates, and gravitational black holes (Hawking radiation). However, to date all predictions are based on semiclassical models, e.g., the Einstein equations and classical space-time metric for a black hole and only the fluctuations are quantized. Here we use a fully quantized dynamical equation, the quantum nonlinear Schrödinger equation, to study the evolution of quantum solitons. As a result of quantum fluctuations in the center-of-mass position, the expectation value of the quantum soliton width increases and concomitantly evaporates through the emission of frequency-entangled photon pairs. The frequency of this emission decreases as the soliton evaporates due to the soliton spreading. In the final phase, the soliton mean field collapses irreversibly into a state with zero mean amplitude. These results may provide insight to quantum evaporation in other systems where a full quantum description is still to be developed and highlights that even classically stable systems may also be subject to quantum evaporation.
2018, Contributo in atti di convegno, ENG
Marcucci G.; Conti C.; Montangero S.; Calarco T.
Controlling quantum nonlinear optical processes is a major challenge in optics. We apply novel quantum control techniques to optical solitons. By phase-space methods, we show that a proper control function alters the soliton evolution.
2018, Articolo in rivista, ENG
Roberto Monaco, Jesper Mygind and Lyudmila V. Filippenko
Confocal Annular Josephson Tunnel Junctions (CAJTJs) which are the natural generalization of the circular annular Josephson tunnel junctions, have a rich nonlinear phenomenology due to the intrinsic non-uniformity of their planar tunnel barrier delimited by two closely spaced confocal ellipses. In the presence of a uniform magnetic field in the barrier plane, the periodically changing width of the elliptical annulus generates a asymmetric double-well for a Josephson vortex trapped in a long and narrow CAJTJ. The preparation and readout of the vortex pinned in one of the two potential minima, which are important for the possible realization of a vortex qubit, have been numerically and experimentally investigated for CAJTJs with the moderate aspect ratio 2:1. In this work we focus on the impact of the annulus eccentricity on the properties of the vortex potential profile and study the depinning mechanism of a fluxon in more eccentric samples with aspect ratio 4:1. We also discuss the effects of the temperature-dependent losses as well as the influence of the current and magnetic noise.
2016, Articolo in rivista, ENG
F. Carbone, D. Dutykh and G. A. El
We undertake a detailed comparison of the results of direct numerical simulations of the soliton gas dynamics for the Korteweg-de Vries equation with the analytical predictions inferred from the exact solutions of the relevant kinetic equation for solitons. Two model problems are considered: i) the propagation of a "trial" soliton through a one-component "cold" soliton gas consisting of randomly distributed solitons of approximately the same amplitude; and ii) the collision of two cold soliton gases of different amplitudes (the soliton gas shock tube problem) leading to the formation of an expanding incoherent dispersive shock wave. In both cases excellent agreement is observed between the analytical predictions of the soliton gas kinetics and the direct numerical simulations. Our results confirm the relevance of the kinetic equation for solitons as a quantitatively accurate model for macroscopic non-equilibrium dynamics of incoherent soliton ensembles.
2016, Articolo in rivista, ENG
Alessandro Cuccoli (a,b,c); Davide Nuzzi (a,b); Ruggero Vaia (d,b); Paola Verrucchi (d,a,b)
Magnetic solitons can constitute a means for manipulating qubits from a distance. This would overcome the necessity of directly applying selective magnetic fields, which is unfeasible in the case of a matrix of qubits embedded in a solid-state quantum device. If the latter contained one-dimensional Heisenberg spin chains coupled to each qubit, one can originate a soliton in a selected chain by applying a time-dependent field at one end of it, far from the qubits. The generation of realistic solitons has been simulated. When a suitable soliton passes by, the coupled qubit undergoes nontrivial operations, even in the presence of moderate thermal noise.
2015, Articolo in rivista, ENG
Luigi Nocera, Laura J Palumbo
We present new elementary, exact weak singular solutions of the steady state, two species, electrostatic, one dimensional Vlasov-Poisson equations. The distribution of the hot, finite mass, mobile ions is assumed to be log singular at the position of the electric potential's minimum. We show that the electron energy distributions on opposite sides of this minimum are not equal. This leads to a jump discontinuity of the electron distribution across its separatrix. A simple relation exists between the difference of these two electron distributions and that of the ions. The velocity Fourier transform of the electron singular distribution is smooth and appears as a simple Neumann series. Elementary, finite amplitude profiles of the electric potential result from Poisson equation, which are smoothly, but nonmonotonically and asymmetrically distributed in space. Two such profiles are given explicitly as appropriate for a nonmonotonic double layer and for a plasma bounded by a surface. The distributions of both electrons and ions supporting such potential meet smooth and kinetically stable boundary conditions at one plasma boundary. For sufficiently small potential to electron temperature ratios, the nonthermal, discontinuous electron distribution resulting at the other plasma boundary is also stable against Landau damped perturbations of the electron distribution.
2012, Articolo in rivista, ENG
Zografopoulos, D.C. 1 and Beccherelli, R. 1 and Kriezis, E.E. 2
Soliton-like propagation of ultra-short pulses in dispersion-engineered silicon photonic wires is theoretically investigated via the nonlinear Schrödinger equation. It is shown that by proper patterning of silicon waveguides, the engineering of group velocity dispersion can effectively compensate for both linear and two-photon absorption-induced nonlinear losses. Quasi-soliton propagation is demonstrated for 100-fs pulses over large propagation lengths for a realistic silicon wire of optimally patterned waveguide width. © 2012 Elsevier B.V. All rights reserved.
2012, Articolo in rivista, ENG
NOCERA L; PALUMBO L J
We investigate the solutions of the kinetic Vlasov-Poisson equations, which govern a plasma made of electrons and one species of mobile ions, in one rectangular dimension. We present a new formulation of Poisson's equation as an integral inverse problem. We prove inversion formulas which allow us to write the solution of this problem in such a way that the energy distribution of either of the particle species is related, in a straightforward way, to the energy distribution of the other species. We show that these distributions are retrieved from the boundary values of suitable sectionally analytic functions. These latter functions are the extension of the particle distributions into their respective complex energy domains
2011, Abstract in atti di convegno, ENG
Claudio Conti (1); Fabio Biancalana (2); Markus A. Schmidt (2); Philip St.J. Russell (2)
We investigate temporal solitons in photonic crystal fibers filled by highly non-instantaneous nonlinear liquids. They can be described by a linear Schroedinger equation, and display peculiar dynamics, as the absence of the Raman self-frequency shift.
2006, Articolo in rivista, ENG
Marcelli R, Nikitov SA, Filimonov YA, Gahshnikov AA, Kozhevnikov AV, Dudko GM
Magnetostatic surface wave (MSSW) bright solitons in a ferrite-dielectric-metal (FDM) structure have been studied experimentally and numerically in the framework of the nonlinear. Schrodinger equation. Attention was focused on the influence of the parametric instability on the soliton formation and propagation. We also discussed the contribution of the nonsolitary (dispersive wave) part of the MSSW pulse on the soliton propagation, to show that their mutual interference leads to the leveling off or to the appearance of some peaks in the MSSW pulse output versus the input amplitude. We have also shown that for MSSW pulses with rectangular shape, the linear pulse compression caused by an induced phase modulation of the input pulse must be taken into account. Experiments were performed on FDM microstrip structures loaded by a 14-mu m-thick yttrium iron garnet film, separated from the ground metal by an air gap with thickness h(1) approximate to 100 mu m or h(2) approximate to 200 mu m. It was found experimentally for MSSW with wavelength lambda approximate to h. that the modulation instability leads to soliton formation for rectangular input pulses with duration T less than the characteristic transient time t* needed for the onset of the parametric instability, while pulses with T >= t* are mainly subjected to parametric instability. The measured threshold amplitudes for parametric and modulation instabilities are in agreement with the theoretical predictions. An influence of additional pumping in the form of both continuous-wave and pulsed signals on the soliton formation was studied. It was shown that an additional pumping signal with duration tau >= t*, and amplitude above the threshold of the parametric instability, suppressed the MSSW soliton. Numerical modeling of the pulsewidth dependence on the microwave power during the propagation in the FDM structure yields results that are in agreement with the experimental observations. Moreover, pulse narrowing due to the induced phase modulation of the input pulse was numerically predicted. All of these effects are in agreement with the experimental findings.
2005, Articolo in rivista
S. Longhi
Electromagnetic localization and the existence of gap solitons in nonlinear metamaterials, which exhibit a stop band in their linear spectral response, is theoretically investigated. For a self-focusing Kerr nonlinearity, the equation for the electric field envelope with carrier frequency in the stop band - where the magnetic permeability ì(ù) is positive and the dielectric permittivity å(ù) is negative - is described by a nonlinear Klein-Gordon equation with a dispersive nonlinear term. A family of standing and moving localized waves for both electric and magnetic fields is found, and the role played by the nonlinear dispersive term on solitary wave stability is discussed.
2003, Articolo in rivista, ENG
Lontano M.; Borghesi M.; Bulanov S.; Esirkepov T.; Farina D.; Naumova N.; Nishihara K.; Passoni M.; Pegoraro F.; Ruhl H.; Sakhorov A.S.; and Willi O.
Low-frequency, relativistic, subcycle solitary waves are found in two-dimensional and three-dimensional particle-intercell (PIC) numerical simulations, as result of the interaction of ultrashort, high-intensity laser pulses with plasmas. Moreover, nondrifting, subcycle relativistic electromagnetic solitons have been obtained as solutions of the hydrodynamic equations for an electron-ion warm plasma, by assuming the quasi-neutrality character of the plasma response. In addition, the formation of long-living macroscopic soliton-like structures has been experimentally observed by means of the proton imaging diagnostics. Several common features result from these investigations, as, for example, the quasi-neutral plasma response to the soliton radiation, in the long-term evolution of the system, which leads to the almost complete expulsion of the plasma from the region where the electromagnetic radiation is concentrated, even at subrelativistic field intensity. The results of the theoretical investigations are reviewed with special attention to these similarities.
2002, Rapporto tecnico, ENG
Lontano M.; Bulanov S.V.; Califano F.; Esirkepov T.Zh.; Farina D.; Koga J.; Liseikina T.V.; Mima K.; Nakajima K.; Naumova N.M.; Nishihara K.; Passoni M.; Pegoraro F.; Ruhl H.; Sentoku Y.; Tajima T.; and Vshivkov V.A.
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2002, Contributo in atti di convegno, ENG
T. Koike, R. Marcelli, Y. Filimonov, S.A. Nikitov and G. Bartolucci
Nonlinear magnetostatic waves (MSWs) have recently received considerable attention for their potentialities in microwave signal processing through the generation of phenomena like modulation instability and solitons, typical of optical devices too. In this paper, the generation of MSW solitons is analyzed from a theoretical and experimental point of view, giving an engineering approach of the problem. The nonlinear Schrödinger equation (NLSE) used for describing the physical effect is here used as a basis for a circuital analysis of a MSW delay line, to model the propagation of nonlinear surface wave pulses. Experimental results are given to confirm the validity of such a model.
2002, Articolo in rivista, ENG
Filimonov, Y.A. , Marcelli, R. , Nikitov, S.A.
The influence of the modulation and parametric four-magnon instabilities on the propagation of magnetostatic surface wave (MSSW) pulses in a delay line configuration has been experimentally studied in a ferrite-dielectric-metal structure. It was possible to distinguish the influence of both instabilities by changing the dispersion properties of the exploited device. The contribution of additional MSSW continuous wave and pulsed signals on the propagation of MSSW pulses has been also considered.
2000, Contributo in atti di convegno, ENG
T. Koike, R. Marcelli and G. Bartolucci
Although nonlinear magnetostatic wave (MSW) propagation in thin YIG films has recently attracted great attention for its potential use in microwave and millimeter wave signal processing devices [1], there has been no effective method to design them using circuit analysis. In this report, we shall discuss a first possible equivalent circuit approach to model the soliton generation and propagation.
2000, Contributo in atti di convegno, ENG
T. Koike, H. Ebihara, R. Marcelli and G. Bartolucci
In this report, we discuss a first possible equivalent circuit approach toward the soliton generation and propagation analysis. To demonstrate the feasibility of this approach, typical experimental parameters were chosen to simulate the soliton behavior. Very good agreement between the experimental result and the simulated result was obtained. This technique will be of great importance in the design of various nonlinear MSW devices and systems in the near future
1999, Articolo in rivista, ENG
Lugiato, Luigi A Narducci; Spinelli, Lorenzo; Tissoni, G.; Brambilla, M.
We consider a model recently proposed, describing a multiple quantum well semiconductor microcavity driven by a coherent holding beam. We discuss here some general features of stationary modulational instabilities affecting the system. By generalizing a method introduced in a previous paper on two-level atoms in optical cavities, we give a detailed description of the stationary instabilities in the parameter space. The modulational instability can be related to the presence of stable cavity solitons, which have been predicted in this system. Therefore we have a helpful tool to research the best parametric conditions for stable cavity solitons, a very demanding task due to the large number of parameters. Finally, we show that our analysis can be extended to more general models, describing a nonlinear diffusive material inside an optical cavity with a general form of the interaction terms. © 1999 IOP Publishing Ltd.