5,238 research outputs found
Nonlinear interfaces: intrinsically nonparaxial regimes and effects
The behaviour of optical solitons at planar nonlinear boundaries is a problem rich in intrinsically nonparaxial regimes that cannot be fully addressed by theories based on the nonlinear Schrödinger equation. For instance, large propagation angles are typically involved in external refraction at interfaces. Using a recently proposed generalized Snell's law for Helmholtz solitons, we analyse two such effects: nonlinear external refraction and total internal reflection at interfaces where internal and external refraction, respectively, would be found in the absence of nonlinearity. The solutions obtained from the full numerical integration of the nonlinear Helmholtz equation show excellent agreement with the theoretical predictions
Universal quantum computation with the Orbital Angular Momentum of a single photon
We prove that a single photon with quantum data encoded in its orbital
angular momentum can be manipulated with simple optical elements to provide any
desired quantum computation. We will show how to build any quantum unitary
operator using beamsplitters, phase shifters, holograms and an extraction gate
based on quantum interrogation. The advantages and challenges of these approach
are then discussed, in particular the problem of the readout of the results.Comment: First version. Comments welcom
Green's functions technique for calculating the emission spectrum in a quantum dot-cavity system
We introduce the Green's functions technique as an alternative theory to the
quantum regression theorem formalism for calculating the two-time correlation
functions in open quantum systems. In particular, we investigate the potential
of this theoretical approach by its application to compute the emission
spectrum of a dissipative system composed by a single quantum dot inside of a
semiconductor cavity. We also describe a simple algorithm based on the Green's
functions technique for calculating the emission spectrum of the quantum dot as
well as of the cavity which can easily be implemented in any numerical linear
algebra package. We find that the Green's functions technique demonstrates a
better accuracy and efficiency in the calculation of the emission spectrum and
it allows to overcome the inherent theoretical difficulties associated to the
direct application of the quantum regression theorem approach
Characterization of dynamical regimes and entanglement sudden death in a microcavity quantum - dot system
The relation between the dynamical regimes (weak and strong coupling) and
entanglement for a dissipative quantum - dot microcavity system is studied. In
the framework of a phenomenological temperature model an analysis in both,
temporal (population dynamics) and frequency domain (photoluminescence) is
carried out in order to identify the associated dynamical behavior. The Wigner
function and concurrence are employed to quantify the entanglement in each
regime. We find that sudden death of entanglement is a typical characteristic
of the strong coupling regime.Comment: To appear in Journal of Physics: Condensed Matte
Helmholtz bright and boundary solitons
We report, for the first time, exact analytical boundary solitons of a generalized cubic-quintic Non-Linear Helmholtz (NLH) equation. These solutions have a linked-plateau topology that is distinct from conventional dark soliton solutions; their amplitude and intensity distributions are spatially delocalized and connect regions of finite and zero wave-field disturbances (suggesting also the classification as 'edge solitons'). Extensive numerical simulations compare the stability properties of recently-reported Helmholtz bright solitons, for this type of polynomial non-linearity, to those of the new boundary solitons. The latter are found to possess a remarkable stability characteristic, exhibiting robustness against perturbations that would otherwise lead to the destabilizing of their bright-soliton counterpart
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