General method for constructing local-hidden-variable models for entangled quantum states

Entanglement allows for the nonlocality of quantum theory, which is the resource behind device-independent quantum information protocols. However, not all entangled quantum states display nonlocality, and a central question is to determine the precise relation between entanglement and nonlocality. Here we present the first general test to decide whether a quantum state is local, and that can be implemented by semidefinite programming. This method can be applied to any given state and for the construction of new examples of states with local hidden-variable models for both projective and general measurements. As applications we provide a lower bound estimate of the fraction of two-qubit local entangled states and present new explicit examples of such states, including those which arise from physical noise models, Bell-diagonal states, and noisy GHZ and W states.Comment: Published version with new title and abstract, improved presentation and new examples of LHV states. Codes are available at https://github.com/paulskrzypczyk/localhiddenstatemodels (please cite this paper if you use them). See also the related work by F. Hirsch et al arXiv:1512.0026

Information causality in multipartite scenarios

Bell nonlocality is one of the most intriguing and counter-intuitive phenomena displayed by quantum systems. Interestingly, such stronger-than-classical quantum correlations are somehow constrained, and one important question to the foundations of quantum theory is whether there is a physical, operational principle responsible for those constraints. One candidate is the information causality principle, which, in some particular cases, is proven to hold for quantum systems and to be violated by stronger-than-quantum correlations. In multipartite scenarios, though, it is known that the original formulation of the information causality principle fails to detect even extremal stronger-than-quantum correlations, thus suggesting that a genuinely multipartite formulation of the principle is necessary. In this work, we advance towards this goal, reporting a new formulation of the information causality principle in multipartite scenarios. By proposing a change of perspective, we obtain multipartite informational inequalities that work as necessary criteria for the principle to hold. We prove that such inequalities hold for all quantum resources, and forbid some stronger-than-quantum ones. Finally, we show that our approach can be strengthened if multiple copies of the resource are available, or, counter-intuitively, if noisy communication channels are employed.Comment: 7+5 pages, 4 figure

An agency model for trade credit policy

Documento de Trabajo 03/05 perteneciente a la colección de documentos de trabajo "Nuevas Tendencias en Dirección de Empresas", dentro del Máster en Investigación en Economía y Empresa.[EN]This article proposes an agency model to explain the trade credit offer to clients. Our model is based on the existence of asymmetric information between sellers and buyers, which results in the appearance of two phenomena known as adverse selection and moral hazard. The former has already been explored by other authors, but not the latter, i.e., the possibility of the buyer not paying the provider. The results obtained indicate that days of sales outstanding of firms are positively related to adverse selection and negatively related to moral hazard. In order to test the moral hazard hypothesis, we use three variables: variable cost, demand elasticity and bad debts. Variable cost and demand elasticity present the expected relation, but bad debts only presents the negative expected relation at low levels, which suggests that when a firm presents high levels of bad debts the risk of the portfolio of clients is also high. In this case, the clients are more likely to present a low liquidity situation and consequently do not take advantage of the use of cash discounts. Traditional models are also tested and compared with the proposed model. We did not find evidence to support tax theory or to support the operational argument of transaction cost theory. We find weak evidence to support the liquidity theory, while the asymmetric information theory was confirmed. A comparison between the agency model proposed and traditional models concluded that the Agency model reached better results in the explanation of the subject of study.This article proposes an agency model to explain the trade credit offer to clients. Our model is based on the existence of asymmetric information between sellers and buyers, which results in the appearance of two phenomena known as adverse selection and moral hazard. The former has already been explored by other authors, but not the latter, i.e., the possibility of the buyer not paying the provider. The results obtained indicate that days of sales outstanding of firms are positively related to adverse selection and negatively related to moral hazard. In order to test the moral hazard hypothesis, we use three variables: variable cost, demand elasticity and bad debts. Variable cost and demand elasticity present the expected relation, but bad debts only presents the negative expected relation at low levels, which suggests that when a firm presents high levels of bad debts the risk of the portfolio of clients is also high. In this case, the clients are more likely to present a low liquidity situation and consequently do not take advantage of the use of cash discounts. Traditional models are also tested and compared with the proposed model. We did not find evidence to support tax theory or to support the operational argument of transaction cost theory. We find weak evidence to support the liquidity theory, while the asymmetric information theory was confirmed. A comparison between the agency model proposed and traditional models concluded that the Agency model reached better results in the explanation of the subject of study

Estimating the volumes of correlations sets in causal networks

Causal networks beyond that in the paradigmatic Bell's theorem can lead to new kinds and applications of non-classical behavior. Their study, however, has been hindered by the fact that they define a non-convex set of correlations and only very incomplete or approximated descriptions have been obtained so far, even for the simplest scenarios. Here, we take a different stance on the problem and consider the relative volume of classical or non-classical correlations a given network gives rise to. Among many other results, we show instances where the inflation technique, arguably the most disseminated tool in the community, is unable to detect a significant portion of the non-classical behaviors. Interestingly, we also show that the use of interventions, a central tool in causal inference, can enhance substantially our ability to witness non-classicality.Comment: 13 pages, 5 figures. Comments are welcom

Arquitetura de hardware dedicada de uma rede neural perceptron para reconhecimento de terreno aplicado a robótica móvel

Monografia (graduação)—Universidade de Brasília, Faculdade UnB Gama, Curso de Engenharia Eletrônica, 2014.Este trabalho visa à implementação em FPGAs (Field Programmable Gate Arrays) de uma rede neural perceptron multicamadas para a classificação de terreno. Para tal, utilizou-se um acelerômetro de 3 eixos para medir as variações de aceleração que um robô sofre em quatro tipos de terreno: arenoso, asfalto, grama e terra. Uma rede neural do tipo perceptron multicamada foi treinada para poder realizar o processo de classificação. Após o treinamento da rede, obteve-se os pesos e os bias da rede para realizar a descrição em hardware e implementação do modelo matemático da rede em FPGAs. Resultados experimentais demonstraram que o desempenho em termos do erro de classificação é melhorado quando os dados de entrada são uma medida estatística da aceleração. Foi usada a média de 32 amostras para compor cada conjunto de entrada da rede. Adicionalmente, os resultados demonstraram que a rede treinada com 8 neurônios na camada escondida alcança o melhor fator custo-benefício. Comparações numéricas entre os resultados obtidos em software e hardware foram realizados para validação da arquitetura, demonstrando a corretude da implementação. Finalmente, os circuitos desenvolvidos foram caracterizados em termos do consumo de recursos, frequência de operação e consumo de potência. O tempo de execução em diversas plataformas embarcadas foi estimado, demonstrando que a arquitetura proposta alcança fatores de aceleração de três ordens de magnitude se comparado com processadores de software embarcados MicroBlaze e Atmel, e quatro vezes se comparado com um processador Intel Core i7. _____________________________________________________________________________ ABSTRACTThis work proposes an FPGA (Field Programmable Gate Arrays) implementation of a multilayer perceptron neural network for terrain classification. A 3-axis accelerometer was used for acquiring the acceleration variation that a robot suffers when moving on four different terrains: sand, asfalt, grass and soil. A multilayer perceptron neural network was trained in order to perform the classification process. Afterwards, the trained weight and bias were used to implement in FPGAs a hardware mathematical model of the proposed network. Experimental results have demonstrated that the network performance in terms of classification error was improved when using statistical values of the acceleration as input data. Thus, the mean value of 32 samples was computed in order to compose the input data set of the proposed neural netwrok. Numerical comparisons between hardware and software results, using the Matlab as statistical estimator, were used for validating the hardware implementation. Finally, the implemented circuits were characterizaed in terms of the consumption of hardware resources, operational frequency and power consumption. The execution time using three software-based embedded platforms were estimated. The proposed architecture achieves speed-up factors of three order of magnitude in comparison with the MicroBlaze and Atmel software processors, as well as, four times in comparision with an Intel Core i7 solution

O ciclismo como prática esportiva e de lazer na Grande Florianópolis: Benefícios à saúde em tempos de pandemia

TCC (Graduação) - Universidade Federal de Santa Catarina. Centro de Desportos. Educação Física - Bacharelado.A situação caótica em que o mundo esteve exposto com a pandemia de COVID-19 em seu auge fez com que toda a população mundial reinventasse a sua forma de viver, de ter lazer e praticar seus esportes. A busca por esportes ao ar livre teve um aumento significativo, sendo assim o objetivo da pesquisa foi investigar aspectos relacionados aos benefícios da prática do ciclismo e compreender os motivos do aumento de número de praticantes durante esse período de pandemia COVID-19 na região da Grande Florianópolis. A metodologia utilizada foi a de pesquisa de campo e explicativa, de natureza aplicada com abordagem quantitativa, onde a coleta de dados, por conta do risco da pandemia, foi feita por meio de um questionário on-line para compreender quais os fatores que levaram as pessoas a escolherem esse esporte e quais os efeitos positivos que elas vêm obtendo com o praticar do ciclismo. Além disso, é questionado a respeito dos fatores que envolvem a segurança da prática e também da responsabilidade governamental para com a modalidade do ciclismo. Os resultados desse trabalho, mesmo que com uma pequena amostra de 68 participantes, foram importantes para verificar o quão positivo foi esse “boom” de vendas de materiais esportivos envolvendo o mundo das bicicletas. Foi constatado que os benefícios sentidos pelos praticantes vão de encontro aos conhecidos na literatura e também foi possível observar o engajamento político para com esse esporte, mesmo que às vezes um pouco negligenciado. Por fim, observou-se que o ciclismo é uma modalidade que traz inúmeros benefícios aos seus adeptos, onde há uma melhoria significativa na qualidade de vida envolvendo bem-estar físico, emocional e social