Collective coherent population trapping in a thermal field

We analyze the efficiency of coherent population trapping (CPT) in a superposition of the ground states of three-level atoms under the influence of the decoherence process induced by a broadband thermal field. We show that in a single atom there is no perfect CPT when the atomic transitions are affected by the thermal field. The perfect CPT may occur when only one of the two atomic transitions is affected by the thermal field. In the case when both atomic transitions are affected by the thermal field, we demonstrate that regardless of the intensity of the thermal field the destructive effect on the CPT can be circumvented by the collective behavior of the atoms. An analytic expression was obtained for the populations of the upper atomic levels which can be considered as a measure of the level of thermal decoherence. The results show that the collective interaction between the atoms can significantly enhance the population trapping in that the population of the upper state decreases with an increased number of atoms. The physical origin of this feature is explained by the semiclassical dressed-atom model of the system. We introduce the concept of multiatom collective coherent population trapping by demonstrating the existence of collective (entangled) states whose storage capacity is larger than that of the equivalent states of independent atoms.

Global Waves with Non-Positive Energy in General Relativity

2000 Mathematics Subject Classification: 35Lxx, 35Pxx, 81Uxx, 83Cxx.

Non-equilibrium properties of trapped ions under sudden application of a laser

Coherent quantum-state manipulation of trapped ions using classical laser fields is a trademark of modern quantum technologies. In this work, we study aspects of work statistics and irreversibility in a single trapped ion due to sudden interaction with the impinging laser. This is clearly an out-of-equilibrium process where work is performed through illumination of an ion by the laser. Starting with the explicit evaluation of the first moments of the work distribution, we proceed to a careful analysis of irreversibility as quantified by the nonequilibrium lag. The treatment employed here is not restricted to the Lamb-Dicke limit, what allows us to investigate the interplay between nonlinearities and irreversibility. We show, for instance, that in the resolved carrier and sideband regimes, variation of the Lamb-Dicke parameter may cause a non-monotonic behavior of the irreversibility indicator. Counterintuitively, we find a working point where nonlinearity helps reversibility, making the sudden quench of the Hamiltonian closer to what would have been obtained quasistatically and isothermally.

La inevitable inconsistencia del Zeus/Júpiter épico

Durante años la investigación literaria ha encontrado fruición en buscar y encontrar inconsistencias narrativas en la Tebaida de Estacio. Concretamente, hay cierto grado de consenso respecto a que las incongruencias en que incurre Júpiter son debidas a negligencia o incuria por parte del poeta. De hecho, no se puede negar que el soberano del cielo se contradice en las ocasiones en que alude a su relación con el Destino. No obstante, no será únicamente el poeta flavio el objeto de mi atención en este artículo. Hoy día se continúa acudiendo a la autoridad filosófica de Séneca (fundamentalmente a Dial. 1.5.8) siempre que el Zeus/Júpiter poshomérico (también el virgiliano) incurre en lo que hemos dado en considerar «incoherencias». Sin embargo, excepción hecha de las composiciones hesiódicas, el estatuto teológico de Zeus/Júpiter es altamente inestable en toda la tradición literaria griega y romana. Quizá deberíamos aceptar, entonces, que durante siglos los que estudiamos literatura antigua hemos tendido a prescindir de la voz autorial y de su autoridad omnímoda para manipular el material literario preexistente con el objeto de generar nuevos significados y nuevas cosmovisiones. En definitiva, nos hemos mostrado proclives a calificar de inconsistencias todo aquello que no se adecua a nuestras expectativas o prejuicios.