High-dimensional quantum cryptography with twisted light

Quantum key distributions (QKD) systems often rely on polarization of light for encoding, thus limiting the amount of information that can be sent per photon and placing tight bounds on the error that such a system can tolerate. Here we describe a proof-of-principle experiment that indicates the feasibility of high-dimensional QKD based on the transverse structure of the light field, allowing for the transfer of more than 1 bit per photon. Our implementation uses the orbital angular momentum (OAM) of photons and the corresponding mutually unbiased basis of angular position (ANG). Our experiment uses a digital micro-mirror device for the rapid generation of OAM and ANG modes at 4 kHz, and a mode sorter capable of sorting single photons based on their OAM and ANG content with a separation efficiency of 93\%. Through the use of a 7-dimensional alphabet encoded in the OAM and ANG bases, we achieve a channel capacity of 2.05 bits per sifted photon. Our experiment shows that, in addition to having an increased information capacity, QKD systems based on spatial-mode encoding will be more tolerant to errors and thus more robust against eavesdropping attacks

Automatic remeshing algorithm of triangular elements during finite element analyses

En este trabajo se presenta un algoritmo de refinamiento automático de elementos finitos triangulares. Es bien sabido que los tamaños de los elementos de la malla juegan un papel importante en el modelado de un medio continuo, particularmente cuando existen diferencias notables en las propiedades de los materiales en zonas contiguas del medio. En tales casos, la malla debe ser lo suficientemente fina en tales áreas con el fin de obtener resultados fiables. Por lo tanto, en este artículo se presenta un algoritmo para llevar a cabo el remallado automático de áreas locales donde se activa el refinamiento de la malla acordemente a los criterios de "remallado". Aquí el algoritmo propuesto, integrado en un programa de computadora de elementos finitos en dos dimensiones, se utiliza para analizar un problema clásico de geotecnia para mostrar la importancia de refinar localmente la malla y para demostrar que, independientemente de las características geométricas de la malla inicial, los resultados del algoritmo son prácticamente iguales. Los cálculos obtenidos con el método propuesto se comparan con la correspondiente solución cerrada del problema, para mostrar la utilidad y fiabilidad del algoritmo de remallado. Por otra parte, con el fin de mostrar la versatilidad del algoritmo, en los casos incluidos en este trabajo se alteran las condiciones de frontera (de carga) consideradas inicialmente con el fin de mostrar cómo el remallado automático local es capaz de adaptar la configuración inicial de la malla en una nueva como una función de las nuevas condiciones de frontera. Como se muestra en el documento, las mallas resultantes obtenidas para ambas condiciones de frontera son sensiblemente diferentes entre sí, lo que conduce a resultados diferentes.In this paper an automatic remeshing algorithm of triangular finite elements is presented. It is well known that the element sizes of the mesh play an important role in modeling the continuum, particularly when notable material properties differences exist in contiguous areas of the medium. In such cases, the mesh must be fine enough in such areas in order to obtain reliable results. Therefore, in this paper is advanced an algorithm to carry out automatic remeshing of local areas where the “remeshing” criteria is activated to refine the mesh accordingly. Herein the proposed algorithm integrated into a two dimensional finite element computer program is used to analyze a classical geotechnical problem to show the importance of locally refining the mesh and to demonstrate that regardless of the geometric characteristics of the initial mesh, the algorithm yields practically equal results. Computations with the proposed method are compared with the corresponding close form solutions, whenever available, to show the usefulness and reliability of the remeshing algorithm. Furthermore, to show the algorithm’s versality, the initial loading boundary conditions considered for the cases included in this paper are modified in order to show how the automatic local remeshing is capable of adapting the initial mesh configuration into a new one as a function of the new boundary conditions. As shown in the paper, the final resulting meshes for both load boundary conditions considered are appreciably dissimilar from each other, which leads to somehow different results.Peer Reviewe

Detection of Baryon Acoustic Oscillation Features in the Large-Scale 3-Point Correlation Function of SDSS BOSS DR12 CMASS Galaxies

We present the large-scale 3-point correlation function (3PCF) of the SDSS DR12 CMASS sample of $777,202$ Luminous Red Galaxies, the largest-ever sample used for a 3PCF or bispectrum measurement. We make the first high-significance ($4.5\sigma$) detection of Baryon Acoustic Oscillations (BAO) in the 3PCF. Using these acoustic features in the 3PCF as a standard ruler, we measure the distance to $z=0.57$ to $1.7\%$ precision (statistical plus systematic). We find $D_{\rm V}= 2024\pm29\;{\rm Mpc\;(stat)}\pm20\;{\rm Mpc\;(sys)}$ for our fiducial cosmology (consistent with Planck 2015) and bias model. This measurement extends the use of the BAO technique from the 2-point correlation function (2PCF) and power spectrum to the 3PCF and opens an avenue for deriving additional cosmological distance information from future large-scale structure redshift surveys such as DESI. Our measured distance scale from the 3PCF is fairly independent from that derived from the pre-reconstruction 2PCF and is equivalent to increasing the length of BOSS by roughly 10\%; reconstruction appears to lower the independence of the distance measurements. Fitting a model including tidal tensor bias yields a moderate significance ($2.6\sigma)$ detection of this bias with a value in agreement with the prediction from local Lagrangian biasing.Comment: 15 pages, 7 figures, submitted MNRA

Quality of life in children with adverse drug reactions: A narrative and systematic review

Aims Adverse drug reactions are a common problem affecting adults and children. The economic impact of the adverse drug reactions has been widely evaluated; however, studies of the impact on the quality of life of children with adverse drug reactions are scarce. The aim was to evaluate studies assessing the health-related quality of life of children with adverse drug reactions. Methods We conducted a systematic review that included the following electronic databases: MEDLINE, EMBASE and the Cochrane Library (including the Cochrane Database of Systematic Reviews, the Database of Abstracts of Reviews of Effects, the Cochrane Controlled Trials Register and the Health Technology Assessment Databases). Results Nine studies were included. Four of the studies were conducted in children with epilepsy; the rest of them involved children with chronic viral hepatitis, Crohn\u27s disease, paediatric cancer and multiple adverse drug reactions compared with healthy children. Based on their findings, authors of all studies concluded that adverse drug reactions had a negative impact on the quality of life of children. No meta-analysis was conducted given the heterogeneous nature of the studies. Conclusions To date, there is no specific instrument that measures quality of life of children with adverse drug reactions, and the information available is poor and variable. In general, adverse drug reactions have a negative impact on the quality of life of affected children. For those interested in this area, more work needs to be done to improve tools that help to evaluate efficiently the health-related quality of life of children with adverse drug reactions and chronic diseases