Enhanced Uplink Quantum Communication with Satellites via Downlink Channels

In developing the global Quantum Internet, quantum communication with low-Earth-orbit satellites will play a pivotal role. Such communication will need to be two way: effective not only in the satellite-to-ground (downlink) channel but also in the ground-to-satellite channel (uplink). Given that losses on this latter channel are significantly larger relative to the former, techniques that can exploit the superior downlink to enhance quantum communication in the uplink should be explored. In this work we do just that - exploring how continuous variable entanglement in the form of two-mode squeezed vacuum (TMSV) states can be used to significantly enhance the fidelity of ground-to-satellite quantum-state transfer relative to direct uplink-transfer. More specifically, through detailed phase-screen simulations of beam evolution through turbulent atmospheres in both the downlink and uplink channels, we demonstrate how a TMSV teleportation channel created by the satellite can be used to dramatically improve the fidelity of uplink coherent-state transfer relative to direct transfer. We then show how this, in turn, leads to the uplink-transmission of a higher alphabet of coherent states. Additionally, we show how non-Gaussian operations acting on the received component of the TMSV state at the ground station can lead to even further enhancement. Since TMSV states can be readily produced in situ on a satellite platform and form a reliable teleportation channel for most quantum states, our work suggests future satellites forming part of the emerging Quantum Internet should be designed with uplink-communication via TMSV teleportation in mind

Application of Computational Fluid Dynamics to the simulation and optimization of multi-environment bioreactors for wastewater treatment

RESUMEN: Los reactores multi-ambiente representan una alternativa innovadora para simplificar los trenes de tratamiento convencionales de Eliminación Biológica de Nutrientes (EBN), ya que son más compactos y pueden adaptarse a los requerimientos de calidad existentes. En concreto, el reactor AnoxAn es capaz de integrar las zonas anaerobia y anóxica del proceso convencional de EBN en un único reactor de flujo ascendente. Sin embargo, su zonificación multi-ambiental y la configuración de elementos singulares dan lugar a un comportamiento hidrodinámico complejo que interfiere en el funcionamiento óptimo del reactor. En por ello que, en la presente tesis doctoral, se realiza un análisis exhaustivo de la hidrodinámica de AnoxAn, así como un estudio la influencia de la misma en la eficiencia biológica del proceso. Para ello, se desarrolla una herramienta numérica basada en Dinámica de Fluidos Computacional (CFD) con el software de código abierto OpenFOAM®, y se propone una metodología para la optimización hidrodinámica de reactores multi-ambiente. Los resultados obtenidos en este trabajo han contribuido al desarrollo tecnológico y operacional de AnoxAn.ABSTRACT: Multi-environment reactors are an innovative alternative to simplify conventional Biological Nutrient Removal (BNR) treatment trains as they are more compact and can adapt to existing quality requirements. Concretely, AnoxAn unifies the anaerobic and anoxic zones of conventional BNR processes in a continuous upflow sludge blanket reactor. However, the multi environmental zoning and singular elements configuration give rise to a complex hydrodynamic behaviour that interferes in the desired biological operation of the reactor. Therefore, in this thesis, a comprehensive hydrodynamic assessment of AnoxAn is carried out, and the influence of the hydraulic behaviour on the biological efficiency of the process is evaluated. For that purpose, a Computational Fluid Dynamics (CFD) based numerical tool is developed with the open source toolbox OpenFOAM®, and a hydrodynamic optimization methodology for multi-environment reactors is proposed. The results obtained in this work have contributed to the development of technological and operational improvements of AnoxAn.A la Universidad de Cantabria primero (PRE03, CVE-2016-11670), y al Ministerio de Educación, Cultura y Deporte del Gobierno de España después (FPU16-05036), por proporcionarme mediante beca la financiación necesaria para la consecución de esta tesis doctoral

Molecular Antennas and Photoactive Nanomaterials based on Energy Transfer Processes

110 p.The scope of this thesis deals is the development and description of photoactive nanomaterials and novel multichromophoric systems as artificial antenna systems. To this aim, the photophysical signatures of luminescent fluorophores (with absorption and emission at different regions of the visible electromagnetic spectrum) encapsulated into inorganic and organic hosts, or assembled in supramolecular structures have been exhaustively characterized. These systems are able to harvest the light over a broad spectral region (ultraviolet-visible) and transfer it to the target place and with a specific energy via successive energy transfer hops. As consequence the excitation can be performed far away from the emission region, improving the photostability of the acceptor emitting dye and a lowering the background interferences. In pursuit of such antennas, different alternatives have been considered, (i) Hybrid materials based on LTL zeolites doped with laser dyes working in the blue, green or red parts of the visible. (ii) Latex nanoparticles doped simultaneously with luminescent fluorophores, leading to stable aqueous colloids. (iii) Molecular cassettes based on energy donor and acceptor dyes covalently linked. All of them undergoing efficient and tunable energy transfer processes, the key factor for a successful development of luminescent antennas. In conclusion, the herein reported approaches (photoactive materials and novel dyes) towards the development of luminescent antennas are shown to be properly applied in photonic fields such as tunable dye lasers, light modulators or polarity probe

Theoretical Study of Pulled Polymer Loops as a Model for Fission Yeast Chromosome

In this thesis, we study the physics of the pulled polymer loops motivated by a biological problem of chromosome alignment during meiosis in fission yeast. During prophase I of meiotic fission yeast, the chromosomes form a loop structure by binding their telomeres to the Spindle Pole Body (SPB). SPB nucleates the growth of microtubules in the cytoplasm. Molecular motors attached to the cell membrane can exert the force on the microtubules and thus pull the whole nucleus. The nucleus performs oscillatory motion from one to the other end of the elongated zygote cell. Experimental evidence suggests that these oscillations facilitate homologous chromosome alignment which is required for the gene recombination. Our goal is to understand the physical mechanism of this alignment. We thus propose a model of pulled polymer loops to represent the chromosomal motion during oscillations. Using a freely-jointed bead-rod model for the pulled polymer loop, we solve the equilibrium statistics of the polymer configurations both in 1D and 3D. In 1D, we find a peculiar mapping of the bead-rod system to a system of particles on a lattice. Utilizing the wealth of tools of the particle system, we solve exactly the 1D stationary measure and map it back to the polymer system. To address the looping geometry, the Brownian Bridge technique is employed. The mean and variance of beads position along the loop are discussed in detail both in 1D and 3D. We then can calculate the three-dimensional statistics of the distance between corresponding beads from a pair of loops in order to discuss the pairing problem of homologous chromosomes. The steady-state shape of a three-dimensional pulled polymer loop is quantified using the descriptors based on the gyration tensor. Beyond the steady state statistics, the relaxation dynamics of the pinned polymer loop in a constant external force field is discussed. In 1D we show the mapping of polymer dynamics to the well-known Asymmetric Simple Exclusion Process (ASEP) model. Our pinned polymer loop is mapped to a half-filled ASEP with reflecting boundaries. We solve the ASEP model exactly by using the generalized Bethe ansatz method. Thus with the help of the ASEP theory, the relaxation time of the polymer problem can be calculated analytically. To test our theoretical predictions, extensive simulations are performed. We find that our theory of relaxation time fit very well to the relaxation time of a 3D polymer in the direction of the external force field. Finally, we discuss the relevance of our findings to the problem of chromosome alignment in fission yeast