135 research outputs found
Generation of entangled photon pairs in optical cavity-QED: Operating in the bad cavity limit
We propose an optical cavity-QED scheme for the deterministic generation of
polarization entangled photon pairs that operates with high fidelity even in
the bad cavity limit. The scheme is based on the interaction of an excited
four-level atom with two empty optical cavity modes via an adiabatic passage
process. Monte-Carlo wave function simulations are used to evaluate the
fidelity of the cavity-QED source and its entanglement capability in the
presence of decoherence. In the bad cavity limit, fidelities close to one are
predicted for state-of-the-art experimental parameter values.Comment: 9 pages and 5 figure
A deterministic cavity-QED source of polarization entangled photon pairs
We present two cavity quantum electrodynamics proposals that, sharing the
same basic elements, allow for the deterministic generation of entangled
photons pairs by means of a three-level atom successively coupled to two single
longitudinal mode high-Q optical resonators presenting polarization degeneracy.
In the faster proposal, the three-level atom yields a polarization entangled
photon pair via two truncated Rabi oscillations, whereas in the adiabatic
proposal a counterintuitive Stimulated Raman Adiabatic Passage process is
considered. Although slower than the former process, this second method is very
efficient and robust under fluctuations of the experimental parameters and,
particularly interesting, almost completely insensitive to atomic decay.Comment: 5 pages, 5 figure
Long-term forecast of thermal mortality with climate warming in riverine amphipods
Forecasting long-term
consequences of global warming requires knowledge on thermal
mortality and how heat stress interacts with other environmental stressors on
different timescales. Here, we describe a flexible analytical framework to forecast
mortality risks by combining laboratory measurements on tolerance and field temperature
records. Our framework incorporates physiological acclimation effects,
temporal scale differences and the ecological reality of fluctuations in temperature,
and other factors such as oxygen. As a proof of concept, we investigated the heat
tolerance of amphipods Dikerogammarus villosus and Echinogammarus trichiatus in the
river Waal, the Netherlands. These organisms were acclimated to different temperatures
and oxygen levels. By integrating experimental data with high-resolution
field
data, we derived the daily heat mortality probabilities for each species under different
oxygen levels, considering current temperatures as well as 1 and 2°C warming
scenarios. By expressing heat stress as a mortality probability rather than a upper
critical temperature, these can be used to calculate cumulative annual mortality, allowing
the scaling up from individuals to populations. Our findings indicate a substantial
increase in annual mortality over the coming decades, driven by projected
increases in summer temperatures. Thermal acclimation and adequate oxygenation
improved heat tolerance and their effects were magnified on longer timescales.
Consequently, acclimation effects appear to be more effective than previously recognized
and crucial for persistence under current temperatures. However, even in
the best-case
scenario, mortality of D. villosus is expected to approach 100% by
2100, while E. trichiatus appears to be less vulnerable with mortality increasing to
60%. Similarly, mortality risks vary spatially: In southern, warmer rivers, riverine animals
will need to shift from the main channel toward the cooler head waters to avoid
thermal mortality. Overall, this framework generates high-resolution
forecasts on
how rising temperatures, in combination with other environmental stressors such as
hypoxia, impact ecological communities.ANID PIA/BASAL FB0002Fondo
Nacional de Desarrollo CientĂfico y
TecnolĂłgico, Grant/Award Number:
1211113Ministerio de Ciencia e
InovaciĂłn, Grant/Award Number: Juan
de la Cierva-formaciĂłn
FellowshipNederlandse Organisatie voor
Wetenschappelijk Onderzoek, Grant/
Award Number: 016.161.32
Nonlinear Instabilities of Multi-Site Breathers in Klein–Gordon Lattices
We explore the possibility of multi-site breather states in a nonlinear Klein–Gordon lattice to become nonlinearly unstable, even if they are found to be spectrally stabl e. The mechanism for this nonlinear instability is through the resonance with the wave continuum of a multiple of an internal mode eigenfrequency in the linearization of excited breather states. For the nonlinear instability, the internal mode must have its Krein signature opposite to that of the wave continuum. This mechanism is not only theoretically proposed, but also numerically corroborated through two concrete examples of the Klein–Gordon lattice with a soft (Morse) and a hard (φ 4) potential. Compared to the case of the nonlinear Schrödinger lattice, the Krein signature of the internal mode relative to that of the wave continuum may change depending on the period of the multi-site breather state. For the periods for which the Krein signatures of the internal mode and the wave continuum coincide, multi-site breather states are observed to be nonlinearly stable
Rogue Waves in Ultracold Bosonic Seas
In this work, we numerically consider the initial value problem for
nonlinear Schrodinger (NLS)-type models arising in the physics of ultracold bosonic
gases, with generic Gaussian wavepacket initial data. The corresponding Gaussian’s
width and, wherever relevant, also its amplitude serve as control parameters. First, we
explore the one-dimensional, standard NLS equation with general power law nonlinearity,
in which large amplitude excitations reminiscent of Peregrine solitons or regular
solitons appear to form, as the width of the relevant Gaussian is varied. Furthermore,
the variation of the nonlinearity exponent aims at exploring the interplay between rogue
waves and the emergence of collapse. The robustness of the main features to noise in
the initial data is also confirmed. To better connect our study with the physics of atomic
condensates, and explore the role of dimensionality effects, we also consider the nonpolynomial
Schrodinger equation, as well as the full three-dimensional NLS equation,
and examine the degree to which relevant considerations generalize.
Eliminar seleccionadosMAT2016-79866-R (AEI/FEDER, UE
Energy Criterion for the Spectral Stability of Discrete Breathers
Discrete breathers are ubiquitous structures in nonlinear anharmonic models ranging from the prototypical example of the Fermi-Pasta-Ulam model to Klein-Gordon nonlinear lattices, among many others. We propose a general criterion for the emergence of instabilities of discrete breathers analogous to the well-established Vakhitov-Kolokolov criterion for solitary waves. The criterion involves the change of monotonicity of the discrete breather’s energy as a function of the breather frequency. Our analysis suggests and numerical results corroborate that breathers with increasing (decreasing) energy-frequency dependence are generically unstable in soft (hard) nonlinear potentials
Nonlinear instabilities of multi-site breathers in Klein–Gordon lattices
In the present work, we explore the possibility of excited breather states in a nonlinear Klein–Gordon lattice to become nonlinearly unstable, even if they are found to be spectrally stable. The mechanism for this fundamentally nonlinear instability is through the resonance with the wave continuum of a multiple of an internal mode eigenfrequency in the linearization of excited breather states. For the nonlinear instability, the internal mode must have its Krein signature opposite to that of the wave continuum. This mechanism is not only theoretically proposed, but also numerically corroborated through two concrete examples of the Klein– Gordon lattice with a soft (Morse) and a hard (φ4) potential. Compared to the case of the nonlinear Schrödinger lattice, the Krein signature of the internal mode relative to that of the wave continuum may change depending on the period of the excited breather state. For the periods for which the Krein signatures of the internal mode and the wave continuum coincide, excited breather states are observed to be nonlinearly stable
Kuznetsov-Ma breather-like solutions in the Salerno model
The Salerno model is a discrete variant of the celebrated nonlinear
Schr\"odinger (NLS) equation interpolating between the discrete NLS (DNLS)
equation and completely integrable Ablowitz-Ladik (AL) model by appropriately
tuning the relevant homotopy parameter. Although the AL model possesses an
explicit time-periodic solution known as the Kuznetsov-Ma (KM) breather, the
existence of time-periodic solutions away from the integrable limit has not
been studied as of yet. It is thus the purpose of this work to shed light on
the existence and stability of time-periodic solutions of the Salerno model. In
particular, we vary the homotopy parameter of the model by employing a
pseudo-arclength continuation algorithm where time-periodic solutions are
identified via fixed-point iterations. We show that the solutions transform
into time-periodic patterns featuring small, yet non-decaying far-field
oscillations. Remarkably, our numerical results support the existence of
previously unknown time-periodic solutions {\it even} at the integrable case
whose stability is explored by using Floquet theory. A continuation of these
patterns towards the DNLS limit is also discussed.Comment: 9 pages, 4 figure
Dark lattice solitons in one-dimensional waveguide arrays with defocusing saturable nonlinearity and alternating couplings
In the present work, we examine “binary” waveguide arrays, where the coupling between adjacent
sites alternates between two distinct values C1 and C2 and a saturable nonlinearity is present on each site.
Motivated by experimental investigations of this type of system in fabricated LiNbO3 arrays, we proceed
to analyze the nonlinear wave excitations arising in the self-defocusing nonlinear regime, examining, in
particular, dark solitons and bubbles. We find that such solutions may, in fact, possess a reasonably wide,
experimentally relevant parametric interval of stability, while they may also feature both prototypical
types of instabilities, namely exponential and oscillatory ones, for the same configuration. The dynamical
manifestation of the instabilities is also examined through direct numerical simulations.MICINN project FIS2008-0484
Discrete Breathers in Klein-Gordon Lattices: a Deflation-Based Approach
Deflation is an efficient numerical technique for identifying new branches of
steady state solutions to nonlinear partial differential equations. Here, we
demonstrate how to extend deflation to discover new periodic orbits in
nonlinear dynamical lattices. We employ our extension to identify discrete
breathers, which are generic exponentially localized, time-periodic solutions
of such lattices. We compare different approaches to using deflation for
periodic orbits, including ones based on a Fourier decomposition of the
solution, as well as ones based on the solution's energy density profile. We
demonstrate the ability of the method to obtain a wide variety of multibreather
solutions without prior knowledge about their spatial profile
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