Equivalence regimes for geometric quantum discord and local quantum uncertainty

The concept of quantum discord aims at unveiling quantum correlations that go beyond those described by entanglement. Its original formulation [L. Henderson and V. Vedral, J. Phys. A: Math. Gen. 34, 6899 (2001); H. Ollivier and W. H. Zurek, Phys. Rev. Lett. 88, 017901 (2001)] is difficult to compute even for the simplest case of two-qubits systems. Alternative formulations have been developed to address this drawback, such as the geometric measure of quantum discord [L. Chang and S. Luo, Phys. Rev. A 87, 062303 (2013)] and the local quantum uncertainty [D. Girolami, T. Tufarelli, and G. Adesso, Phys. Rev. Lett. 110, 240402 (2013)] that can be evaluated in closed form for some quantum systems, such as two-qubit systems. We show here that these two measures of quantum discord are equivalent for 2×D dimensional bipartite quantum systems. By considering the relevant example of N00N states for phase estimation in lossy environments, we also show that both metrics of quantum discord quantify the decrease of quantum Fisher information of the phase estimation protocol. Given their ease of computation in 2×D bipartite systems, the geometric measure of quantum discord and the local quantum uncertainty demonstrate their relevance as computable measures of quantum discord.We acknowledge support from the Spanish Ministry of Economy and Competitiveness (“Severo Ochoa” program for Centres of Excellence in R&D No. SEV-2015-0522), from Fundacio Privada Cellex, from Fundacio Mir-Puig, and from Generalitat de Catalunya through the CERCA program. This work was partially funded through the EMPIR project 17FUN01-BeCOMe. The EMPIR initiative is cofunded by the European Union Horizon 2020 Research and Innovation Programme and the EMPIR participating states. A.V. acknowledges financial support from PREBIST that has received funding from the European Union Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 754558. J.R.A. acknowledges funding by the European Union Horizon 2020 Research and Innovation Programme (Marie Sklodowska- Curie 765075-LIMQUET). R.J.L.M. thankfully acknowledges financial support by CONACyT under the project CB-2016-01/284372, and by Direcci n General de Asuntos del Personal Acad mico, Universidad Nacional Aut noma de M xico (DGAPA-UNAM), under the project UNAM-PAPIIT IN102920.Peer ReviewedPostprint (author's final draft

Exceptional points of any order in a single, lossy waveguide beam splitter by photon-number-resolved detection

Exceptional points (EPs) are degeneracies of non-Hermitian operators where, in addition to the eigenvalues, the corresponding eigenmodes become degenerate. Classical and quantum photonic systems with EPs have attracted tremendous attention due to their unusual properties, topological features, and an enhanced sensitivity that depends on the order of the EP, i.e., the number of degenerate eigenmodes. Yet, experimentally engineering higher-order EPs in classical or quantum domains remain an open challenge due to the stringent symmetry constraints that are required for the coalescence of multiple eigenmodes. Here, we analytically show that the number-resolved dynamics of a single, lossy waveguide beam splitter, excited by indistinguishable photons and post-selected to the -photon subspace, will exhibit an EP of order +1. By using the well-established mapping between a beam splitter Hamiltonian and the perfect state transfer model in the photon-number space, we analytically obtain the time evolution of a general -photon state and numerically simulate the system’s evolution in the post-selected manifold. Our results pave the way toward realizing robust, arbitrary-order EPs on demand in a single device

Evolution of differences in clinical presentation across epidemic waves among patients with COVID-like-symptoms who received care at the Mexican Social Security Institute

BackgroundTimely monitoring of SARS-CoV-2 variants is crucial to effectively managing both prevention and treatment efforts. In this paper, we aim to describe demographic and clinical patterns of individuals with COVID-19-like symptoms during the first three epidemic waves in Mexico to identify changes in those patterns that may reflect differences determined by virus variants.MethodsWe conducted a descriptive analysis of a large database containing records for all individuals who sought care at the Mexican Social Security Institute (IMSS) due to COVID-19-like symptoms from March 2020 to October 2021 (4.48 million records). We described the clinical and demographic profile of individuals tested (3.38 million, 32% with PCR and 68% with rapid test) by test result (positives and negatives) and untested, and among those tested, and the changes in those profiles across the first three epidemic waves.ResultsIndividuals with COVID-19-like symptoms were older in the first wave and younger in the third one (the mean age for those positive was 46.6 in the first wave and 36.1 in the third wave; for negatives and not-tested, the mean age was 41 and 38.5 in the first wave and 34.3 and 33.5 in the third wave). As the pandemic progressed, an increasing number of individuals sought care for suspected COVID-19. The positivity rate decreased over time but remained well over the recommended 5%. The pattern of presenting symptoms changed over time, with some of those symptoms decreasing over time (dyspnea 40.6 to 14.0%, cough 80.4 to 76.2%, fever 77.5 to 65.2%, headache 80.3 to 78.5%), and some increasing (odynophagia 48.7 to 58.5%, rhinorrhea 28.6 to 47.5%, anosmia 11.8 to 23.2%, dysgeusia 11.2 to 23.2%).ConclusionDuring epidemic surges, the general consensus was that any individual presenting with respiratory symptoms was a suspected COVID-19 case. However, symptoms and signs are dynamic, with clinical patterns changing not only with the evolution of the virus but also with demographic changes in the affected population. A better understanding of these changing patterns is needed to improve preparedness for future surges and pandemics

Noise-assisted energy transport in electrical oscillator networks with off-diagonal dynamical disorder

Noise is generally thought as detrimental for energy transport in coupled oscillator networks. However, it has been shown that for certain coherently evolving systems, the presence of noise can enhance, somehow unexpectedly, their transport efficiency; a phenomenon called environment-assisted quantum transport (ENAQT) or dephasing-assisted transport. Here, we report on the experimental observation of such effect in a network of coupled electrical oscillators. We demonstrate that by introducing stochastic fluctuations in one of the couplings of the network, a relative enhancement in the energy transport efficiency of 22.5 ± 3.6% can be observed.Peer ReviewedPostprint (published version

Study protocol of effectiveness of a biopsychosocial multidisciplinary intervention in the evolution of non-speficic sub-acute low back pain in the working population : cluster randomised trial

Background: Non-specific low back pain is a common cause for consultation with the general practitioner, generating increased health and social costs. This study will analyse the effectiveness of a multidisciplinary intervention to reduce disability, severity of pain, anxiety and depression, to improve quality of life and to reduce the incidence of chronic low back pain in the working population with non-specific low back pain, compared to usual clinical care. Methods/Design: A Cluster randomised clinical trial will be conducted in 38 Primary Health Care Centres located in Barcelona, Spain and its surrounding areas. The centres are randomly allocated to the multidisciplinary intervention or to usual clinical care. Patients between 18 and 65 years old (n = 932; 466 per arm) and with a diagnostic of a non-specific sub-acute low back pain are included. Patients in the intervention group are receiving the recommendations of clinical practice guidelines, in addition to a biopsychosocial multidisciplinary intervention consisting of group educational sessions lasting a total of 10 hours. The main outcome is change in the score in the Roland Morris disability questionnaire at three months after onset of pain. Other outcomes are severity of pain, quality of life, duration of current non-specific low back pain episode, work sick leave and duration, Fear Avoidance Beliefs and Goldberg Questionnaires. Outcomes will be assessed at baseline, 3, 6 and 12 months. Analysis will be by intention to treat. The intervention effect will be assessed through the standard error of measurement and the effect-size. Responsiveness of each scale will be evaluated by standardised response mean and receiver-operating characteristic method. Recovery according to the patient will be used as an external criterion. A multilevel regression will be performed on repeated measures. The time until the current episode of low back pain takes to subside will be analysed by Cox regression. Discussion: We hope to provide evidence of the effectiveness of the proposed biopsychosocial multidisciplinary intervention in avoiding the chronification of low back pain, and to reduce the duration of non-specific low back pain episodes. If the intervention is effective, it could be applied to Primary Health Care Centres

Reactores electroquímicos filtro prensa a escala laboratorio: escalado y efecto entrada/salida

Este trabajo presenta un una experiencia sencilla y útil para estudiantes de la Licenciatura en Química e Ingeniería Química. Su objetivo se centra en obtener una mayor comprensión de la importancia del tamaño en los reactores electroquímicos a escala laboratorio a la hora de realizar posibles escalados a tamaños superiores. Los resultados obtenidos en células de pequeñas dimensiones no siempre son extrapolables a células de tamaño superior debido a que las condiciones de trabajo a escala laboratorio no siempre son extrapolables

Emergence of a negative resistance in noisy coupled linear oscillators

We report on the experimental observation of an emerging negative resistance in a system of coupled linear electronic RLC harmonic oscillators under the influence of multiplicative noise with long correlation time. When two oscillators are coupled by a noisy inductor, an analysis in the Fourier space of the electrical variables unveils the presence of an effective negative resistance, which acts as an energy transport facilitator. This might constitute a simple explanation of the now fashionable problem of energy transport assisted by noise in classical systems. The experimental setup is based on the working principle of an analog computer and by itself constitutes a versatile platform for studying energy transport in noisy systems by means of coupled electrical oscillator systems