Density operator of a system pumped with polaritons: A Jaynes-Cummings like approach

We investigate the effects of considering two different incoherent pumpings over a microcavity-quantum dot system modelled using the Jaynes-Cummings Hamiltonian. When the system is incoherently pumped with polaritons it is able to sustain a large number of photons inside the cavity with Poisson-like statistics in the stationary limit, and also leads to a separable exciton-photon state. We also investigate the effects of both types of pumpings (Excitonic and Polaritonic) in the emission spectrum of the cavity. We show that the polaritonic pumping as considered here is unable to modify the dynamical regimes of the system as the excitonics pumping does. Finally, we obtain a closed form expression for the negativity of the density matrices that the quantum master equation considered here generates.Comment: 16 pages, 4 figure

Sistemas caóticos y su aplicación a la encriptación de señales

La sincronización y control de señales caóticas es una activa área de investigación por sus posibles aplicaciones en telecomunicaciones y transmisión de señales [1, 2, 3, 4]. En el presente trabajo se estudia un sistema de comunicación basado en la sincronización de dos sistemas no lineales caóticos, cada uno modelado a partir de las ecuaciones de movimiento de un péndulo forzado amortiguado y que se encuentran en el mismo punto de operación del espacio de parámetros. Synchronization and control of chaotic signals is an active research area because of its applications in telecommunications and secure signal transmission [1,2,3,4]. In this work a communication system based in the synchronization of two chaotic nonlinear systems, each one being modeled by the motion equations of a driven damped pendulum and operated in the same parameter space region is shown. Two communication channels were used: the first one for the synchronizing signal and the second one for the sent message. By using two channels the initial conditions sensibility problem is solved. In the receiver system a feedback loop as a proportional controller is used in order to drive quickly the error between the decoder and encoder states to zero. The last two facts make the system to be robust to external pertubative signals such as noise in the communication channels

Entanglement and phase transitions in a exciton-polariton bec confined in a photonic crystal nanocavity

In this work we study a polariton-exciton system confined in photonic crystal nanocavity with embedded quantum dot. Using a separable state of the type BCS, for the matter subsystem, product by a coherent state, for the photonic mode, we compute the ground state energy of N polaritons. Also, we characterize the quantum coherence in the system using entanglement and discord, calculated both from the pair density matrix. Finally, we introduce temperature and magnetic field to our model and we obtain signatures of phase transitions in the quantum correlations of the system.En este trabajo estudiamos un sistema de polaritones excitónicos con_nado en punto cuántico embebido en una nanocavidad de cristal fotónico. Usando un estado separable del tipo BCS, para el subsistema excitónico confinado en el punto cuántico, y un estado coherente, para el modo electromagnético con_nado en la nanocavidad, se calcula la energía del estado base para el sistema de N polaritones excitónicos. También se realiza una caracterización de las coherencias cuánticas del sistema calculando discordia y entrelazamiento a partir de la llamada matriz densidad de pares. Finalmente, introduciendo temperatura y campo magnético en nuestro modelo, podemos evidenciar la señal de una posible transición de fase en las correlaciones cuánticas del sistema

The Degasperis-Procesi equation as a non-metric Euler equation

In this paper we present a geometric interpretation of the periodic Degasperis-Procesi equation as the geodesic flow of a right invariant symmetric linear connection on the diffeomorphism group of the circle. We also show that for any evolution in the family of $b$-equations there is neither gain nor loss of the spatial regularity of solutions. This in turn allows us to view the Degasperis-Procesi and the Camassa-Holm equation as an ODE on the Fr\'echet space of all smooth functions on the circle.Comment: 17 page

ESTUDIO TEÓRICO DEL ESPECTRO DE EMISIÓN PARA UN SISTEMA MICROCAVIDAD-PUNTO CUÁNTICO EN UNA APROXIMACIÓN DE CAMPO MEDIO

En este trabajo, se obtiene una expresión numérica para calcular el espectro de emisión de un sistema microcavidad-punto cuántico usando una teoría de campo medio en el formalismo de la matriz densidad. El sistema modelado es un micropilar semiconductor que contiene un único punto cuántico en el interior de la microcavidad, este sistema presenta pérdida de fotones a través de los espejos de la cavidad y bombeo de excitones al punto cuántico. Obtenemos una ecuación maestra de campo medio no lineal que nos permite calcular el espectro de emisión.In this work, we deduce a numerical expression to calculate the emission spectrum for a quantum dot-microcavity system, using a mean field theory in the density matrix formalism. The open system modeled, is a typical semiconductor micropillar that contains a single quantum dot inside a microcavity, this system presents leakage of photons through cavity mirrors and pumping of excitons to the quantum dot. We obtain a mean field nonlinear master equation that allow us calculate the emission spectrum

Coulomb matrix elements of bilayers of confined charge carriers with arbitrary spatial separation

We describe a practical procedure to calculate the Coulomb matrix elements of 2D spatially separated and confined charge carriers, which are needed for detailed theoretical descriptions of important condensed matter finite systems. We derive an analytical expression, for arbitrary separations, in terms of a single infinite series and apply a u-type Levin transform in order to accelerate the resulting infinite series. This procedure has proven to be efficient and accurate. Direct consequences concerning the functional dependence of the matrix elements on the separation distance, transition amplitudes and the diagonalization of a single electron-hole pair in vertically stacked parabolic quantum dots are presented.Comment: 8 page

Synchronized chaotic phase masks for encrypting and decrypting images

This paper presents an alternative to secure exchange of encrypted information through public open channels. Chaotic encryption introduces a security improvement by an efficient masking of the message with a chaotic signal. Message extraction by an authorized end user is done using a synchronization procedure, thus allowing a continuous change of the encrypting and decrypting keys. And optical implementation with a 4f optical encrypting architecture is suggested. Digital simulations, including the effects of missing data, corrupted data and noise addition are shown. These results proof the consistency of the proposal, and demonstrate a practical way to operate with it.Facultad de IngenieríaCentro de Investigaciones ÓpticasUID en Óptica, Procesamiento de Imágenes y Metrología Óptic