Collapse and revival oscillations as a probe for the tunneling amplitude in an ultra-cold Bose gas

We present a theoretical study of the quantum corrections to the revival time due to finite tunneling in the collapse and revival of matter wave interference after a quantum quench. We study hard-core bosons in a superlattice potential and the Bose-Hubbard model by means of exact numerical approaches and mean-field theory. We consider systems without and with a trapping potential present. We show that the quantum corrections to the revival time can be used to accurately determine the value of the hopping parameter in experiments with ultracold bosons in optical lattices.Comment: 10 pages, 12 figures, typos in section 3A correcte

Non-Poissonian statistics from Poissonian light sources with application to passive decoy state quantum key distribution

We propose a method to prepare different non-Poissonian signal pulses from sources of Poissonian photon number distribution using only linear optical elements and threshold photon detectors. This method allows a simple passive preparation of decoy states for quantum key distribution. We show that the resulting key rates are comparable to the performance of active choices of intensities of Poissonian signals.Comment: 7 pages, 3 figures, accepted for publication in Opt. Let

Global Growth and Trends of In-Body Communication Research—Insight From Bibliometric Analysis

A bibliometric analysis was conducted to examine research on in-body communication. This study aimed to assess the research growth in different countries, identify influential authors for potential international collaboration, investigate research challenges, and explore future prospects for in-body communication. A total of 148 articles written in English from journals and conference proceedings were gathered from the Scopus database. These articles cover the period from 2006 until August 2023. VOS Viewer 1.6.19 and Tableau Cloud were used to analyze the data. The analysis reveals that research on in-body communication has shown fluctuations but overall tends to increase. The United States, Finland, and Japan were identified as the leading countries (top three) in terms of publication quantity, while researchers from Norway, Finland, and Morocco received the highest number of citations. The University of Oulu in Finland has emerged as a productive institution in this field. Collaborative research opportunities exist with the countries mentioned above or with authors who have expertise in this topic. The dominant research topic within this field pertains to ultra-wideband (UWB) technology. One of the future challenges in this field is the exploration of optical wireless communication (OWC) as a potential communication medium for in-body devices, such as electronic devices implanted in the human body. This includes improving performance to meet the requirements for in-body communication devices. Additionally, this paper provides further insights into the progress of research on OWC for in-body communication conducted in our laboratory

Passive sources for the Bennett-Brassard 1984 quantum key distribution protocol with practical signals

Most experimental realizations of quantum key distribution are based on the Bennett-Brassard 1984 (so-called BB84) protocol. In a typical optical implementation of this scheme, the sender uses an active source to produce the required BB84 signal states. While active state preparation of BB84 signals is a simple and elegant solution in principle, in practice passive state preparation might be desirable in some scenarios, for instance, in those experimental setups operating at high transmission rates. Passive schemes might also be more robust against side-channel attacks than active sources. Typical passive devices involve parametric down-conversion. In this paper, we show that both coherent light and practical single photon sources are also suitable for passive generation of BB84 signal states. Our method does not require any external-driven element, but only linear optical components and photodetectors. In the case of coherent light, the resulting key rate is similar to the one delivered by an active source. When the sender uses practical single photon sources, however, the distance covered by a passive transmitter might be longer than the one of an active configuration.Comment: 14 pages, 11 figure

Formació i tecnologies de la traducció

Aquest número de la Revista Tradumàtica proposa una reflexió sobre la necessària imbricació entre les tecnologies i la formació de traductors. L’objectiu és presentar punts de vista diferents i sovint complementaris relacionats amb els diversos papers que hi entren en joc: interessa saber el que pensen les persones responsables de la formació i conèixer quines característiques té l’oferta docent, però també convé veure com es situen els estudiants. D’igual manera volem pensar en el futur, sense perdre de vista el present d’un context tan àgil i canviant com el que es descriu aquí.Este número de la Revista Tradumàtica propone una reflexión sobre la necesaria imbricación entre las tecnologías y la formación de traductores. El objetivo es presentar puntos de vista diferentes y a menudo complementarios relacionados con los diversos papeles que entran en juego: interesa saber lo que piensan las personas responsables de la formación y conocer las características de la oferta docente, pero también conviene ver como se sitúan los estudiantes. De igual manera queremos pensar en el futuro, pero sin perder de vista el presente de un contexto tan ágil y cambiante como el que aquí se describe

Isothermal Titration Calorimetry and Transmission Electron Microscopy of Main-Chain Viologen Polymer Containing Bromide as Counerions

Polyelectrolytes are an important class of macromolecules that contain dissociable ionic groups. When introduced into polar solvent, usually the universal solvent water, dissociation takes place so that electrically charged macromolecule is suspended in solution. The electrostatic interaction is operative between ionized groups inside the macromolecule, between the macromolecules, between the counterions, and between the macromolecule and counterion. Since this interaction is characterized by its long-range nature, the solution exhibits various interesting properties including the polyelectrolyte behavior very different from solutions of neutral polymers

Influencia de los modelos intuitivos en la comprensión de la multiplicación y la división

Since the stdy by Fischbein et al. (1985) which suggested that children develop intuitive models about multiplication and division early, much research has offered data that corroborate these models. In this study we analyze the differential weight of the models in three kid of task: algorithms, problem solving, and problem posing. We included two age groups (1st of ESO and 8th of EGB), and three kid of quantities (whole numbers, decimals and fractions). The results indicated that the intuitive models did not have the same differential weight for the different tasks. For instance, the problem posing task did not seem suited to the conditions under which the intuitive models act. Likewise, the presence of quantities that failed to observe one or more restrictions of the models did not have a negative influence. In contrast, the errors committed in the two remaining tasks were almost exclusively due to the application of the intuitive rules.A partir del trabajo de Fischbein et al. (1985) que sugiere que los niños construyen tempranamente modelos intuitivos sobre la multiplicación y división, numerosas investigaciones han ofrecido datos consistentes con estos modelos. En este estudio analizamos el peso diferencial de los modelos en tres tipos de tareas: resolver algoritmes, resolver problemas y plantear problemas. Hemos incluido también dos grupos de edad (1º de ESO y 8º de EGB), asi como tres tipos de cantidades (enteros, decimales y fracciones). LoS resultados indicaron que los modelos intuitivos no tuvieron el mismo peso diferencial en las diferentes tareas. Por ejemplo, la tarea de plantear problemas no parecía reunir las condiciones bajo las que actúan los modelos intuitivos. Asimismo, la presencia de cantidades que alteraban una o más imposiciones de los modelos no influyó negativamente. Por el contrario, los errores de las dos tareas restantes se debieron a la aplicación de las reglas intuitivas

Neutron rich nuclei in density dependent relativistic Hartree-Fock theory with isovector mesons

Density dependent relativistic Hartree-Fock theory has been extended to describe properties of exotic nuclei. The effects of Fock exchange terms and of pi - and rho - meson contributions are discussed. These effects are found to be more important for neutron rich nuclei than for nuclei near the valley of stability.Comment: 10 pages, 5 figures, LaTeX, macro packages graphicx and time

Upper bounds for the secure key rate of decoy state quantum key distribution

The use of decoy states in quantum key distribution (QKD) has provided a method for substantially increasing the secret key rate and distance that can be covered by QKD protocols with practical signals. The security analysis of these schemes, however, leaves open the possibility that the development of better proof techniques, or better classical post-processing methods, might further improve their performance in realistic scenarios. In this paper, we derive upper bounds on the secure key rate for decoy state QKD. These bounds are based basically only on the classical correlations established by the legitimate users during the quantum communication phase of the protocol. The only assumption about the possible post-processing methods is that double click events are randomly assigned to single click events. Further we consider only secure key rates based on the uncalibrated device scenario which assigns imperfections such as detection inefficiency to the eavesdropper. Our analysis relies on two preconditions for secure two-way and one-way QKD: The legitimate users need to prove that there exists no separable state (in the case of two-way QKD), or that there exists no quantum state having a symmetric extension (one-way QKD), that is compatible with the available measurements results. Both criteria have been previously applied to evaluate single-photon implementations of QKD. Here we use them to investigate a realistic source of weak coherent pulses. The resulting upper bounds can be formulated as a convex optimization problem known as a semidefinite program which can be efficiently solved. For the standard four-state QKD protocol, they are quite close to known lower bounds, thus showing that there are clear limits to the further improvement of classical post-processing techniques in decoy state QKD.Comment: 10 pages, 3 figure

Tri-Bimaximal Neutrino Mixing from Discrete Symmetry in Extra Dimensions

We discuss a particularly symmetric model of neutrino mixings where, with good accuracy, the atmospheric mixing angle theta_{23} is maximal, theta_{13}=0 and the solar angle satisfies sin^2(theta_{12})=1/3 (Harrison-Perkins-Scott (HPS) matrix). The discrete symmetry A_4 is a suitable symmetry group for the realization of this type of model. We construct a model where the HPS matrix is exactly obtained in a first approximation without imposing ad hoc relations among parameters. The crucial issue of the required VEV alignment in the scalar sector is discussed and we present a natural solution of this problem based on a formulation with extra dimensions. We study the corrections from higher dimensionality operators allowed by the symmetries of the model and discuss the conditions on the cut-off scales and the VEVs in order for these corrections to be completely under control. Finally, the observed hierarchy of charged lepton masses is obtained by assuming a larger flavour symmetry. We also show that, under general conditions, a maximal theta_{23} can never arise from an exact flavour symmetry.Comment: 24 pages, 1 figure, misprints corrected and references adde