States interpolating between number and coherent states and their interaction with atomic systems

Using the eigenvalue definition of binomial states we construct new intermediate number-coherent states which reduce to number and coherent states in two different limits. We reveal the connection of these intermediate states with photon-added coherent states and investigate their non-classical properties and quasi-probability distributions in detail. It is of interest to note that these new states, which interpolate between coherent states and number states, neither of which exhibit squeezing, are nevertheless squeezed states. A scheme to produce these states is proposed. We also study the interaction of these states with atomic systems in the framework of the two-photon Jaynes-Cummings model, and describe the response of the atomic system as it varies between the pure Rabi oscillation and the collapse-revival mode and investigate field observables such as photon number distribution, entropy and the Q-function.Comment: 26 pages, 29 EPS figures, Latex, Accepted for publication in J.Phys.

Density matrix reconstruction from displaced photon number distributions

We consider state reconstruction from the measurement statistics of phase space observables generated by photon number states. The results are obtained by inverting certain infinite matrices. In particular, we obtain reconstruction formulas, each of which involves only a single phase space observable.Comment: 19 page

Hole burning in a nanomechanical resonator coupled to a Cooper pair box

We propose a scheme to create holes in the statistical distribution of excitations of a nanomechanical resonator. It employs a controllable coupling between this system and a Cooper pair box. The success probability and the fidelity are calculated and compared with those obtained in the atom-field system via distinct schemes. As an application we show how to use the hole-burning scheme to prepare (low excited) Fock states.Comment: 7 pages, 10 figure

Preparation and control of a cavity-field state through atom-driven field interaction: towards long-lived mesoscopic states

The preparation of mesoscopic states of the radiation and matter fields through atom-field interactions has been achieved in recent years and employed for a range of striking applications in quantum optics. Here we present a technique for the preparation and control of a cavity mode which, besides interacting with a two-level atom, is simultaneously submitted to linear and parametric amplification processes. The role of the amplification-controlling fields in the achievement of real mesoscopic states, is to produce highly-squeezed field states and, consequently, to increase both: i) the distance in phase space between the components of the prepared superpositions and ii) the mean photon number of such superpositions. When submitting the squeezed superposition states to the action of similarly squeezed reservoirs, we demonstrate that under specific conditions the decoherence time of the states becomes independent of both the distance in phase space between their components and their mean photon number. An explanation is presented to support this remarkable result, together with a discussion on the experimental implementation of our proposal. We also show how to produce number states with fidelities higher than those derived as circular states

Negativity of the Wigner function as an indicator of nonclassicality

A measure of nonclassicality of quantum states based on the volume of the negative part of the Wigner function is proposed. We analyze this quantity for Fock states, squeezed displaced Fock states and cat-like states defined as coherent superposition of two Gaussian wave packets.Comment: 10 pages, 7 figure

Engineering arbitrary motional ionic state through realistic intensity-fluctuating laser pulses

We present a reliable scheme for engineering arbitrary motional ionic states through an adaptation of the projection synthesis technique for trapped-ion phenomena. Starting from a prepared coherent motional state, the Wigner function of the desired state is thus sculpted from a Gaussian distribution. The engineering process has also been developed to take into account the errors arising from intensity fluctuations in the exciting-laser pulses required for manipulating the electronic and vibrational states of the trapped ion. To this end, a recently developed phenomenological-operator approach that allows for the influence of noise will be applied. This approach furnishes a straightforward technique to estimate the fidelity of the prepared state in the presence of errors, precluding the usual extensive ab initio calculations. The results obtained here by the phenomenological approach, to account for the effects of noise in our engineering scheme, can be directly applied to any other process involving trapped-ion phenomena.Comment: more information at http://www.df.ufscar.br/~quantum

Spontaneous emission in a planar Fabry-Perot microcavity

Published versio

Preparation of nonclassical states in cavities with a moving mirror

Published versio

Desafíos políticos de los países de inmigración

13 págs.-- Publicado en "Confluencia XXI. Revista de Pensamiento Político" (México), nº 3 (Oct-Dic 2008) bajo el título monográfico "Migrantes: ¿Por qué se van? ¿Por qué se quedan?".Las migraciones, una práctica tan antigua como la propia condición humana, se han convertido en un factor estructural de primer orden, en uno de los macrofenómenos más definitorios de nuestra época y en un complejo reto para las sociedades contemporáneas. En prácticamente todos los países del mundo, todo lo que concierne a este complejo fenómeno ocupa un lugar destacado en la agenda política. La gestión, el control y la integración de los movimientos internacionales de personas se presentan como un policy field de creciente y prioritaria relevancia. No se trata, sin embargo, de una cuestión de mera moda: el número de países implicados de manera significativa en las migraciones internacionales ha aumentado considerablemente, hasta el punto de que resulta realmente difícil encontrar algún Estado que no sea bien un país de inmigración, bien un país de emigración o bien ambas cosas a la vez, cuando no al menos un país de tránsito. No ha de extrañar entonces que la mayoría de los gobiernos haya tomado conciencia de la necesidad de ofrecer una respuesta en términos legales e institucionales a un fenómeno de carácter permanente que puede llegar a alterar la estructura demográfica, social, cultural, económica y laboral de un país. Dada la complejidad de la cuestión, y por cuestiones de economía argumentativa, aquí se abordará de manera fundamental desde la perspectiva de los países receptores, que, por lo demás, es también la adoptada en forma habitual por los países europeos que registran mayor inmigración. Sin embargo, el fenómeno migratorio es fundamentalmente transnacional y tiene fehacientes repercusiones en los países de emigración.Peer reviewe