Quantum-based spectroscopy and efficient energy transport with biomolecules

For many years, the fields of quantum optics and biology have rarely shared a common path. In quantum optics, most of the concepts and techniques developed over the years stand for systems where only a few degrees of freedom are considered and, more importantly, where the systems under study are assumed to be completely isolated from their surrounding environment. This situation is far from what we can find in nature. Biological complexes are, by definition, warm, wet and noisy systems subjected to environmental fluctuations, where quantum phenomena are unlikely to be observed. Notwithstanding, in recent years, this paradigm has begun to be questioned by several works where quantum-mechanical concepts have been introduced in order to describe the dynamics of important biological processes, such as energy transport in photosynthetic light-harvesting complexes. The goal of this thesis is twofold. Firstly, we will investigate how ideas and techniques routinely used in quantum optics can be exploited in order to develop new quantum-based spectroscopy techniques and, secondly, we will examine to what extent microscopic quantum phenomena could impact on the efficient transport behavior of photosynthetic light-havesting complexes. This problem is particularly relevant, because the understanding of the fundamental mechanisms that enable the highly efficient transport of energy in photosynthetic systems could lead us to the design of future quantum-inspired light-harvesting technologies, such as high-efficiency organic solar cells.Por muchos años, los campos de la óptica cuántica y la biología raramente han compartido un mismo camino. En la óptica cuántica, la mayoría de los conceptos y técnicas desarrolladas a lo largo de los años son válidas sólo en sistemas donde un número pequeño de grados de libertad es considerado y, más importante aún, donde se asume que los sistemas bajo estudio están completamente aislados del medio ambiente que los rodea. Esta situación está muy lejos de lo que podemos encontrar en la naturaleza. Los complejos biológicos son, por definición, sistemas a altas temperaturas, sujetos a fluctuaciones, en los cuales se cree que los fenómenos cuánticos son imposibles de observar. Sin embargo, en años recientes, esta creencia ha sido cuestionada por diferentes trabajos en los que conceptos de mecánica cuántica han sido usados con el objetivo de describir la dinámica de procesos biológicos de gran importancia como, por ejemplo, el transporte de energía en los complejos de captación de luz en sistemas fotosintéticos. El objetivo de esta tesis se divide en dos. Primeramente, investigaremos cómo las ideas y técnicas usadas comunmente en óptica cuántica pueden ser explotadas con el objetivo de desarrollar nuevas técnicas de espectroscopía y, segundo, estudiaremos hasta que punto los fenómenos cuánticos microscópicos pueden influir en el comportamiento del transporte eficiente de energía en sistemas fotosintéticos de captación de luz. Este problema es particularmente relevante, pues el entender los mecanismos fundamentales que permiten un eficiente transporte de energía en sistemas fotosintéticos nos podría conducir al diseño de nuevas tecnologías de captación y recolección de energía como, por ejemplo, celdas solares orgánicas de alta eficiencia

Nonlinear coherent states for the Susskind-Glogower operators

We construct nonlinear coherent states for the Susskind-Glogower operators by the application of the displacement operator on the vacuum state. We also construct nonlinear coherent states as eigenfunctions of a Hamiltonian constructed with the Susskind-Glogower operators. We generalize the solution of the eigen- function problem to an arbitrary |mi initial condition. To analyze the obtained results, we plot the Husimi Q function, the photon number probability distribution and the Mandel Q-parameter. For both cases, we find that the constructed states exhibit interesting nonclassical features, such as amplitude squeezing and quantum interferences due to a self-splitting into two coherent-like states. Additionally, we show that non- linear coherent states may be modeled by propagating light in semi-infinite arrays of optical fibers.Comment: 22 pages, 8 figures, Conference Quantum Optics V, Published as: REVISTA MEXICANA DE F\'ISICA S 57 (3) 133-14

All-cause mortality in the cohorts of the Spanish AIDS Research Network (RIS) compared with the general population: 1997Ł2010

Abstract Background: Combination antiretroviral therapy (cART) has produced significant changes in mortality of HIVinfected persons. Our objective was to estimate mortality rates, standardized mortality ratios and excess mortality rates of cohorts of the AIDS Research Network (RIS) (CoRIS-MD and CoRIS) compared to the general population. Methods: We analysed data of CoRIS-MD and CoRIS cohorts from 1997 to 2010. We calculated: (i) all-cause mortality rates, (ii) standardized mortality ratio (SMR) and (iii) excess mortality rates for both cohort for 100 personyears (py) of follow-up, comparing all-cause mortality with that of the general population of similar age and gender. Results: Between 1997 and 2010, 8,214 HIV positive subjects were included, 2,453 (29.9%) in CoRIS-MD and 5,761 (70.1%) in CoRIS and 294 deaths were registered. All-cause mortality rate was 1.02 (95% CI 0.91-1.15) per 100 py, SMR was 6.8 (95% CI 5.9-7.9) and excess mortality rate was 0.8 (95% CI 0.7-0.9) per 100 py. Mortality was higher in patients with AIDS, hepatitis C virus (HCV) co-infection, and those from CoRIS-MD cohort (1997. Conclusion: Mortality among HIV-positive persons remains higher than that of the general population of similar age and sex, with significant differences depending on the history of AIDS or HCV coinfection

Compilación de Proyectos de Investigacion de 1984-2002

Instituto Politecnico Nacional. UPIICS