We present a general method for obtaining all Bell inequalities for a given experimental setup. Although the algorithm runs slowly, we apply it to two cases. First, the Greenberger-Horne-Zeilinger setup with three observers each performing one of two possible measurements. Second, the case of two observers each performing one of three possible experiments. In both cases we obtain hundreds of inequalities. Since this is the set of all inequalities, the one that is maximally violated in a given quantum state must (...) be among them. We demonstrate this fact with a few examples. We also note the deep connection between the inequalities and classical logic, and their violation with quantum logic. (shrink)

Localist models of spreading activation (SA) and models assuming distributed representations offer very different takes on semantic priming, a widely investigated paradigm in word recognition and semantic memory research. In this study, we implemented SA in an attractor neural network model with distributed representations and created a unified framework for the two approaches. Our models assume a synaptic depression mechanism leading to autonomous transitions between encoded memory patterns (latching dynamics), which account for the major characteristics of automatic semantic priming in (...) humans. Using computer simulations, we demonstrated how findings that challenged attractor‐based networks in the past, such as mediated and asymmetric priming, are a natural consequence of our present model’s dynamics. Puzzling results regarding backward priming were also given a straightforward explanation. In addition, the current model addresses some of the differences between semantic and associative relatedness and explains how these differences interact with stimulus onset asynchrony in priming experiments. (shrink)

We develop and defend the thesis that the Hilbert space formalism of quantum mechanics is a new theory of probability. The theory, like its classical counterpart, consists of an algebra of events, and the probability measures defined on it. The construction proceeds in the following steps: (a) Axioms for the algebra of events are introduced following Birkhoff and von Neumann. All axioms, except the one that expresses the uncertainty principle, are shared with the classical event space. The only models for (...) the set of axioms are lattices of subspaces of inner product spaces over a field K. (b) Another axiom due to Soler forces K to be the field of real, or complex numbers, or the quaternions. We suggest a probabilistic reading of Soler's axiom. (c) Gleason's theorem fully characterizes the probability measures on the algebra of events, so that Born's rule is derived. (d) Gleason's theorem is equivalent to the existence of a certain finite set of rays, with a particular orthogonality graph (Wondergraph). Consequently, all aspects of quantum probability can be derived from rational probability assignments to finite "quantum gambles". (e) All experimental aspects of entanglement- the violation of Bell's inequality in particular- are explained as natural outcomes of the probabilistic structure. (f) We hypothesize that even in the absence of decoherence macroscopic entanglement can very rarely be observed, and provide a precise conjecture to that effect .We also discuss the relation of the present approach to quantum logic, realism and truth, and the measurement problem. (shrink)

In the mid-nineteenth century George Boole formulated his ‘conditions of possible experience’. These are equations and ineqaulities that the relative frequencies of events must satisfy. Some of Boole's conditions have been rediscovered in more recent years by physicists, including Bell inequalities, Clauser Horne inequalities, and many others. In this paper, the nature of Boole's conditions and their relation to propositional logic is explained, and the puzzle associated with their violation by quantum frequencies is investigated in relation to a variety of (...) approaches to the interpretation of quantum mechanics. * While preparing this paper for publication I have learnt of the untimely death of Professor J. S. Bell, and I wish to dedicate the paper to his memory. This research was undertaken while I spent a sabbatical leave at Wolfson College, and the History and Philosophy of Science Department at the University of Cambridge. I would like to thank Michael Redhead and Jeremy Butterfield for their hospitality and for helpful discussions. A first draft of this paper has been distributed among the participants of the conference 'Einstein in Context' which was held in Israel, in April 1990.1 have benefited from the comments of many colleagues. I would like to thank in particular Arthur Fine who enlightened me on the prism models, David Albert. Maya Bar-Hillel. Yemima Ben-Menachem, Mara Beller. Simon Saunders, and Mark Steiner. This research is partially supported by the Edelstein Center for the History and Philosophy of Science at the Hebrew University. (shrink)

The intuition guiding the de…nition of computation has shifted over time, a process that is re‡ected in the changing formulations of the Church-Turing thesis. The theory of computation began with logic and gradually moved to the capacity of …nite automata. Consequently, modern computer models rely on general physical principles, with quantum computers representing the extreme case. The paper discusses this development, and the challenges to the Church-Turing thesis in its physical form, in particular, Kieu’s quantum computer and relativistic hyper-computation. Finally, (...) the robustness of the boundary between polynomial and exponential time complexity is considered in connection with quantum computers and quantum information theory. (shrink)

According to a prominent view in Jewish-Halakhic literature, “mitzvot (commandments) require intention.” That is, to fulfill one’s obligation in performing a commandment, one must intend to perform the act because it’s a mitzvah; one must take the fact that one’s act is a mitzvah as her reason for doing the action. I argue that thus understood, this Halakhic view faces a revised version of Thomas Hurka’s recent dilemma for structurally similar views in ethics: either it makes it a necessary condition (...) for the act’s being a mitzvah that one has a false belief about the act’s Halakhic status, or it commits proponents of the “mitzvot require intention” view to a sort of rational failure in performing the mitzvot. The dilemma arises, however, only if we interpret this Halakhic view as requiring one to have a belief about her act’s Halakhic status in order for it to have this status. I suggest that the dilemma can be avoided by interpreting the intention requirement as requiring a make-belief, instead of a belief. Under this understanding, Halakha (or God) doesn’t care about why one performs an act of a mitzvah, but rather about how she does it; how she sees and experiences her action. This suggests another form of worship central to Judaism—worship via make-believing. (shrink)

This book compares various approaches to the interpretation of quantum mechanics, in particular those which are related to the key words "the Copenhagen interpretation", "the antirealist view", "quantum logic" and "hidden variable theory". Using the concept of "correlation" carefully analyzed in the context of classical probability and in quantum theory, the author provides a framework to compare these approaches. He also develops an extension of probability theory to construct a local hidden variable theory. The book should be of interest for (...) physicists and philosophers of science interested in the foundations of quantum theory. (shrink)

Kuhnʼs influential book, The Structure of Scientific Revolutions,1 is often viewed as a revolt against empiricist philosophy of science. However, Friedman has reminded us lately2 that the book was commissioned by logical positivists, who were delighted with the result. In fact, the book was part of the International Encyclopedia of United Science initiated by members of the Vienna Circle, whose first volumes were published in 1938.3 The project aimed at providing a systematic positivist perspective on all the sciences, from logic (...) and mathematics through linguistics and on to psychology and sociology. The publication of Structure as volume 12 of the encyclopedia was greeted enthusiastically by the editor, Carnap, as can be learned from the letters he wrote to Kuhn. There are several reasons for this reaction. First, as noted by Friedman, there is a resemblance between Kuhnʼs notion of changing paradigms and Carnapʼs philosophical ideas. Logical empiricism is “logical” because of its central tenet that scientific knowledge is the organization of facts within a conceptual structure; the existence of an appropriate conceptual structure is a precondition for the very possibility of scientific inquiry. Unlike Kant, however, the logical empiricists believed that the conceptual. (shrink)

Semantic priming has long been recognized to reflect, along with automatic semantic mechanisms, the contribution of controlled strategies. However, previous theories of controlled priming were mostly qualitative, lacking common grounds with modern mathematical models of automatic priming based on neural networks. Recently, we introduced a novel attractor network model of automatic semantic priming with latching dynamics. Here, we extend this work to show how the same model can also account for important findings regarding controlled processes. Assuming the rate of semantic (...) transitions in the network can be adapted using simple reinforcement learning, we show how basic findings attributed to controlled processes in priming can be achieved, including their dependency on stimulus onset asynchrony and relatedness proportion and their unique effect on associative, category-exemplar, mediated and backward prime-target relations. We discuss how our mechanism relates to the classic expectancy theory and how it can be further extended in future developments of the model. (shrink)

_Resumo_: este artigo analisa a interpretação de Foucault sobre Kant com o foco na complexidade das relações entre o trabalho filosófico, em geral, e o mundo concreto. O escopo do artigo é delimitado por esta análise de Foucault, especialmente, sobre dois textos de Kant: _O que é o iluminismo? _e _Antropologia de um ponto de vista pragmático_. Investiga-se a possibilidade de um acesso a um espaço anterior a qualquer orientação ética específica, deslocando-se, assim, do conjunto de elaborações éticas da tradição (...) filosófica. Primeiramente, destacam-se os diferentes posicionamentos possíveis assumidos pelos filósofos, em geral, em seu trabalho perante o mundo concreto. A seguir mostra-se a existência de uma ambigüidade latente no trabalho filosófico, a qual permite concluir que há sim um espaço prévio, dentro do qual o filósofo pode ou não compreender a sua situação histórica e o seu lugar no mundo. Todos estes elementos são expostos mediante o acompanhamento da análise realizada por Foucault. (shrink)

Israel’s discursive strategy for legitimizing the displacement of Palestinians in 1948 involved describing it as part of a regional “population exchange.” This argument contributed to three critical characteristics of Israeli citizenship. First, it solidified an understanding of citizenship as a negation of persecution and a haven for would-be Jewish refugees. Second, it tied Mizrahi claims against states across the Middle East to Palestinian claims against Israel. Israel thus exploited Mizrahi refugee rights for its geostrategic interests—a fight against the claims of (...) Palestinian refugees. This had detrimental material consequences for both groups. Third, this strategy contributed to the construction of Palestinians as an “exchangeable remainder” and a demographic threat that could potentially pose a risk to the Jewish majority. Ultimately, Israel irrevocably entangled the displacement histories of three groups: Ashkenazi Jews, Mizrahi Jews, and Arab Palestinians. This Gordian knot remains with us today, and is reflected in a stratified Israeli society. But the vision that this symposium suggests we consider, that of “historical justice,” demands that it be undone. This Article therefore offers a way in which the refugee histories could perhaps one day be disentangled: a program of reparations for the Mizrahi and Palestinian citizens of Israel. (shrink)

Ideology and self-interest are often in tension. If positive political theorists assume broad self-interest as the standard of human behaviour, they can accommodate people’s ideological motivation to act for the common good. Yet, their theories may become tautological and empirically untestable. Conversely, if these theorists assume narrow self-interest, they increase testability. But because ideology seems incompatible with narrow self-interest, they often rule ideology out as a motivational driver. Positive political theorists can, however, combine ideology with narrow self-interest by assuming broad (...) egoism. And in so doing, they should assume that ideology motivates political agents until it becomes too costly for these agents’ material interests. (shrink)

Quantum theory has played a significant role in modern philosophy both as a source of metaphysical ideas and as an important example of a 'scientific revolution'. In spite of the sixty or so years that have elapsed since its invention, a long lasting controversy concerning the interpretation and meaning of quantum theory prevails. Almost all authors, however, seem to agree on one major point, namely, that there could be no interpretation of this theory which is both realistic and local. ;The (...) purpose of this thesis is to demonstrate that this premiss is false and that a realistic, local and deterministic interpretation of quantum theory does exist, provided that we extend the classical concept of probability. ;In order to establish this a 'quasi classical' probability theory is developed based on some non Lebesgue measurable 'events', which is then applied to account for spin-statistics. Finally I note how this model reflects on the problems of physical realism, locality, the status of probability theory and the philosophical foundations of mathematics. (shrink)

Resumo : este artigo analisa a apropriação que Agamben faz das concepções heideggerianas de facticidade e Ereignis. Esta apropriação é analisada dentro do escopo da obra Homo Sacer. O desenvolvimento destas duas seções busca responder a seguinte pergunta: como se explica a passagem da ontologia para dentro da filosofia política em Agamben? Para responder esta pergunta, na primeira seção, busca-se compreender uma ampliação possível dos problemas da dominação da técnica. Na segunda seção, estes problemas são submetidos a uma perspectiva biolítica (...) apresentada por Agamben. A resposta mostra que Agamben aproxima as concepções de Heidegger com o tema da indistinção entre poder constituinte e poder constituído, direcionando-se para uma releitura da relação potência e ato com o poder. (shrink)

Este artigo trata sobre a filosofia de Agamben com o enfoque no tema dos processos de subjetivação. A investigação busca responder a seguinte interrogação: o que significam tais processos para Agamben? Compreende-se que Agamben possui uma definição diferente daquela usada por Focault. Assim, a exposição recupera elementos relacionados aos processos de subjetivação. Entre estes elementos estão os dispositivos e o sujeito. Através da análise dos dispositivos, mostra-se que Agamben amplia o conceito, primeiramente elaborado por Focault, inserindo-o na análise do mundo (...) capitalista atual. Através desse aprofundamento a respeito do dispositivo, chega-se a uma definição dos processos de subjetivação. Na segunda parte, os resultados dos processos de subjetivação, isto é, o sujeito capturado frente o seu destino político. Isto permite consolidar a explicação dos processos de subjetivação que foi alcançada. O resultado final mostra que os processos de subjetivação devem ser não ignorados, mas superados para que o sujeito possua uma vida em potência. (shrink)

A deterministic model that accounts for the statistical behavior of random samples of identical particles is presented. The model is based on some nonmeasurable distribution of spin values in all directions. The mathematical existence of such distributions is proved by set-theoretical techniques, and the relation between these distributions and observed frequencies is explored within an appropriate extension of probability theory. The relation between quantum mechanics and the model is specified. The model is shown to be consistent with known polarization phenomena (...) and the existence of macroscopic magnetism. Finally.. (shrink)

Statistical learning is often taken to lie at the heart of many cognitive tasks, including the acquisition of language. One particular task in which probabilistic models have achieved considerable success is the segmentation of speech into words. However, these models have mostly been tested against English data, and as a result little is known about how a statistical learning mechanism copes with input regularities that arise from the structural properties of different languages. This study focuses on statistical word segmentation in (...) Arabic, a Semitic language in which words are built around consonantal roots. We hypothesize that segmentation in such languages is facilitated by tracking consonant distributions independently from intervening vowels. Previous studies have shown that human learners can track consonant probabilities across intervening vowels in artificial languages, but it is unknown to what extent this ability would be beneficial in the segmentation of natural language. We assessed the performance of a Bayesian segmentation model on English and Arabic, comparing consonant-only representations with full representations. In addition, we examined to what extent structurally different proto-lexicons reflect adult language. The results suggest that for a child learning a Semitic language, separating consonants from vowels is beneficial for segmentation. These findings indicate that probabilistic models require appropriate linguistic representations in order to effectively meet the challenges of language acquisition. (shrink)

O objetivo deste artigo, que se insere no âmbito da filosofia da religião, é tratar o problema lógico do mal e mais concretamente a teoria da defesa do livre-arbítrio de Alvin Plantinga. Quero examinar se esta é uma teoria plausível e se resiste a algumas objeções. Pretendo defender que esta teoria parece resistir a certas objeções.

We consider the set of all matrices of the form pij = tr[W (Ei ⊗ Fj)] where Ei, Fj are projections on a Hilbert space H, and W is some state on H ⊗ H. We derive the basic properties of this set, compare it with the classical range of probability, and note how its properties may be related to a geometric measures of entanglement.

Consider the set Q of quantum correlation vectors for two observers, each with two possible binary measurements. Quadric (hyperbolic) inequalities which are satis…ed by every q 2 Q are proved, and equality holds on a two dimensional manifold consisting of the local boxes, and all..

This paper offers a new semantic theory of existentials (sentences of the form There be NP pivot XP coda ) in which pivots are (second order) predicates and codas are modifiers. The theory retains the analysis of pivots as denoting generalized quantifiers (Barwise and Cooper 1981; Keenan 1987), but departs from previous analyses in analyzing codas as contextual modifiers on a par with temporal/locative frame adverbials. Existing analyses universally assume that pivots are arguments of some predicate, and that codas are (...) main or secondary predicates. It is shown that these analyses cannot account for the behavior of codas with quantifiers and for the interaction of multiple codas, both of which receive a simple treatment on the proposed theory. The assimilation of codas to frame adverbials explains several semantic properties which have not been analyzed in the semantic literature, and that distinguish existentials from their copular counterparts. Furthermore, it highlights important properties of the semantics of modification and its relation to predication. (shrink)

Resenha do livro de Ceticismo e Naturalismo: algumas variedades, de P. F. Strawson. Traduçáo de Jaimir Conte. Sáo Leopoldo: Editora Unisinos, 2008, 114 páginas.

Let be n events in a probability space, and suppose that we have only partial information about the distribution: The probabilites of the events themselves, and their pair intersections. With this partial information we cannot, usually, deternine the probability of an event B in the algebra generated by the 's, but we can obtain lower and upper bounds. This is done by a linear program related to the correlation polytope c(n), a structure introduced in [3], [4]. In the first part (...) of the paper I demonstrate how laws of large numbers (for sequences of events which are not necessarily independent) can be proved, using only the duality theorem of linear programming. These include the weak law of large numbers (necessary and sufficient condition) and various sufficient conditions for strong laws. The connection between these laws and the facet structure of the correlation polytope is established. In the second part of the paper I consider a more general case. Assume that our information consists of the values of the probabilities of all intersections of the 's up to size k, k < n. The techniques of linear programming lead naturally to an application of the theory of polynomial approximation in estimating the size of various events. In particular, I prove an approximate version of the central limit theorem. (shrink)

Contemporary versions of Bell’s argument against local hidden variable (LHV) theories are based on the Clauser Horne Shimony and Holt (CHSH) inequality, and various attempts to generalize it. The amount of violation of these inequalities cannot exceed the bound set by the Grothendieck constants. However, if we go back to the original derivation by Bell, and use the perfect anticorrelation embodied in the singlet spin state, we can go beyond these bounds. In this paper we derive two-particle Bell inequalities for (...) traceless two-outcome observables, whose violation in the singlet spin state go beyond the Grothendieck constant both for the two and three dimensional cases. Moreover, creating a higher dimensional analog of perfect correlations, and applying a recent result of Alon and his associates (Invent. Math. 163 499 (2006)) we prove that there are two-particle Bell inequalities for traceless two-outcome observables whose violation increases to in…nity as the dimension and number of measurements grow. Technically these result are possible because perfect correlations (or anti-correlations) allow us to transport the indices of the inequality from the edges of a bipartite graph to those of the complete graph. Finally, it is shown how to apply these results to mixed Werner states, provided that the noise does not exceed 20%. (shrink)

O presente estudo teve como objeto a Sociedade de São Vicente de Paulo - SSVP, e visou analisar a crise institucional da associação, relacionando-a com a crise religiosa contemporânea, tendo em vista a dificuldade na admissão de novos quadros para a entidade, como também a complexidade da manutenção de seus membros. A motivação do trabalho foi compreender como a crise socioreligiosa contemporânea contribui para esse processo, valendo-se também da observação empírica nas reuniões, festas e eventos realizados pela instituição. Buscou-se ainda (...) identificar alguns fatores externos e internos à instituição, e suas implicações, que estão contribuindo para esse desequilíbrio. Para isso, foi utilizado como método principal de coleta de dados a pesquisa bibliográfica, em fontes e documentos da SSVP, como a Regra e o Regulamento; boletins, revistas e atas da entidade, como também obras de autores que estudam a SSVP. Houve também, metodologicamente, a observação através da presença numa Conferência Vicentina, pertencente ao Conselho Central Sagrados Corações. Bibliograficamente, ainda foram analisadas algumas obras de pesquisadores que refletem sobre a realidade religiosa contemporânea, abordando temas como secularização, modernidade, pluralismo religioso, crise de sentido, transmissão religiosa, crise religiosa contemporânea, mobilidade social e religiosa e juventude, a fim de entender de que maneira tais temas podem ajudar na análise do catolicismo e, consequentemente, da crise institucional da SSVP. A dissertação procurou refletir sobre perspectivas e as novas demandas sociais que podem desafiar a entidade a dialogar com a sociedade contemporânea, especialmente com os jovens, oferecendo um horizonte de renovação e de futuro para o carisma da entidade. Para uma entidade centenária, se tornou difícil para os próprios vicentinos incluir seus familiares, sobretudo os próprios filhos, para o trabalho dentro da associação. A análise realizada confirmou a hipótese que realmente a entidade atravessa uma crise sem precedentes e que serão necessárias inovações, aberturas, estratégias e novas pedagogias, se houver interesse em mudar, enfrentar os desafios atuais e renovar a SSVP e seu carisma. Para isso, ela precisará contar com a força e o dinamismo da juventude e de seus membros e dirigentes. A pesquisa realizada no Programa de Pós-graduação em Ciências da Religião da PUC Minas foi desenvolvida na Área de Concentração “Religião e Cultura” e na Linha de Pesquisa “Religião, Política e Educação”. (shrink)

Esta investigação trata da diferença entre as áreas da filosofia, mas essa diferenciação necessita de uma forma plausível e não dogmática em seu proceder. Para encontrar uma forma de diferenciar cada área interna da filosofia, utilizou-se uma comparação inicial com as ciências e se buscou oprocesso argumentativo como um fator principal de diferenciação. Isso se expressa mais diretamente no problema de pesquisa, que visa a investigar se as diferentes áreas filosóficas também possuem diferentes processos deargumentação. A relevância desta investigação se (...) encontra na identificação de determinadas tensões entre as áreas filosóficas. O resultado mostra que os diferentes conteúdos tratados pelas distintas áreas filosóficas exercem um efeito importante sobre os processos argumentativos. Para fins de delimitação, optou-se por duas áreas da filosofia: a lógica e a ética. (shrink)

We describe a possible physical device that computes a function that cannot be computed by a Turing machine. The device is physical in the sense that it is compatible with General Relativity. We discuss some objections, focusing on those which deny that the device is either a computer or computes a function that is not Turing computable. Finally, we argue that the existence of the device does not refute the Church–Turing thesis, but nevertheless may be a counterexample to Gandy's thesis.

A classical gas at equilibrium satisfies the locality conditionif the correlations between local fluctuations at a pair of remote small regions diminish in the thermodynamic limit. The gas satisfies a strong locality conditionif the local fluctuations at any number of remote locations have no (pair, triple, quadruple....) correlations among them in the thermodynamic limit. We prove that locality is equivalent to a certain factorizability condition on the distribution function. The analogous quantum condition fails in the case of a freeBose gas. (...) Next we prove that strong locality is equivalent to the total factorizability of the distribution function, and thus (given Liourille’s theorem) to the Maxwell Boltzmann distribution for an ideal gas. (shrink)

We develop a systematic approach to quantum probability as a theory of rational betting in quantum gambles. In these games of chance, the agent is betting in advance on the outcomes of several (finitely many) incompatible measurements. One of the measurements is subsequently chosen and performed and the money placed on the other measurements is returned to the agent. We show how the rules of rational betting imply all the interesting features of quantum probability, even in such finite gambles. These (...) include the uncertainty principle and the violation of Bell's inequality among others. Quantum gambles are closely related to quantum logic and provide a new semantics for it. We conclude with a philosophical discussion on the interpretation of quantum mechanics. (shrink)

Suppose someone is brought up as an orthodox Jew, and so only eats kosher, is very conservative sexually, etc. Suppose they then find out that this Judaism stuff is just all a big mistake. If they then regret all the shrimp they could have eaten, all the sex!, this makes perfect sense. Not so, however, if someone finds out that moral realism is false, and they now regret all the fun they could have had hurting people’s feeling, etc. Even if (...) this does make sense, there’s a strong disanalogy between the moral and the religious case. This asymmetry, on a realist picture of morality, calls for explanation. This chapter tries to explain it. The discussion engages some topics familiar from objections to Robust realism—the why-be-moral challenge, the status of de-dicto moral motivation, and whether and why we should care about the moral properties, robustly realistically understood. (shrink)

The paper proposes a solution to the problem with Odysseus’ kingship in the Odyssey by maintaining that Odysseus is not officially considered dead. Consequently, Telemachus cannot inherit the position of king and Penelope must leave Odysseus’ household before remarrying. After discussing the modern concept of legal death and previous interpretations of the Ithacan situation, the paper focusses on Athena's speech at 1.275–92. A close reading demonstrates that erecting a cenotaph to Odysseus would be tantamount to a modern declaration of death (...) in absentia, since it will render Penelope a widow and Telemachus the head of the household. This legal convention chimes with the Homeric depiction of Hades. (shrink)

Este trabalho é uma proposta de ensino de sintaxe para os cursos de Licenciatura em Letras. Os objetivos que me levaram a escrever este texto foram os seguintes: reabrir a discussão acerca da necessidade de revisar o que sugere a Nomenclatura Gramatical Brasileira no âmbito da análise sintática; reinvindicar o reconhecimento da noção de sintagma como unidade sintática construída hierarquicamente e localizada entre o vocábulo e a sentença; e reconhecer dois níveis de estruturação sintática – oracional e suboracional –, em (...) vez da tríplice partição da NGB – termos essenciais, termos integrantes e termos acessórios. As ideias aqui defendidas estão fundamentadas nos pressupostos teóricos da Gramática Gerativa, mais especificamente no modelo de Princípios e Parâmentros, bem como em propostas alicerçadas na Linguística de Texto. (shrink)

Why don't we see large macroscopic objects in entangled states? Even if the particles composing the object were all entangled and insulated from the environment, we shall still find it almost always impossible to observe the superposition. The reason is that as the number of particles n grows, we need an ever more careful preparation, and an ever more carefully designed experiment, in order to recognize the entangled character of the state of the object. An observable W that distinguishes all (...) the unentangled states from some entangled states is called a witness. We consider witnesses on n quantum bits (qbits), and use the following normalization: A witness W satisfies |tr(Wr)|<= 1 for all separable states r, while ||W|| >1, with the norm being the maximum among the absolute values of the eigenvalues of W. Although there are n-qbit witnesses whose norm is exponential in n, we conjecture that for a large majority of such witnesses ||W||<=O[(nlogn)^1/2]. We prove this conjecture for the family of extremal witnesses introduced by Werner and Wolf (Phys. Rev. A 64, 032112 (2001)). Assuming the conjecture is valid we argue that multiparticle entanglement can be detected only if a system has been carefully prepared in a very special state. Otherwise, multiparticle entanglement lies below the threshold of detection, even if it exists, and even if decoherence has been ``turned off''. (shrink)

More specifically, one notices that X1  X2, P1  P2  0 where X1, X2 are the position operators for the first and second particles respectively, and P1, P2 their momenta operators. This means that, in principle, one can prepare the pair of particles with simultaneously known values of X1  X2 and P1  P2. Then the knowledge of the value of P2 allows to infer the value of P1.(However, performing the experiment with these continuous variables is technically (...) impossible and it remains a thought experiment.). (shrink)

In a fundamental paper [Phys. Rev. Lett. 78, 325 (1997)] Grover showed how a quantum computer can …nd a single marked object in a database of size N by using only O(pN ) queries of the oracle that identi…es the object. His result was generalized to the case of …nding one object in a subset of marked elements. We consider the following computational problem: A subset of marked elements is given whose number of elements is either M or K, M (...) < K, our task is to determine which is the case. We show how to solve this problem with a high probability of success using only iterations of Grover’s basic step (and no other algorithm). Let m be the required number of iterations; we prove that under certain restrictions on the sizes of M and K the estimation.. (shrink)

A local "resolution" of the Einstein-Podolsky-Rosen Paradox by way of a mechanical analogue (roul ette) is presented together with some notes regarding the consequences of such models for the foundations of mathematics and the theory of probability.

Este artigo trata sobre as possíveis aproximações entre a filosofia de Heidegger e a filosofia de Heidegger. Essas aproximações são desenvolvidas em função do mundo cotidiano. Busca-se esclarecer quais são as dificuldades envolvidas no estudo de ambos os autores, quando a intenção visa diretamente o ser humano, sendo esses elementos identificados com cotidiano. Na primeira e na segunda parte apresentam-se os dois autores e na terceira parte é realizada uma interface através da filosofia de Tugendhat. Nela se destaca a crítica (...) à Heidegger e a adoção de uma posição naturalista. Conclui-se que tanto Heidegger quanto Hume possuem âmbitos subjacentes que determinam a suas análises do cotidiano. Estes âmbitos subjacentes se diferenciam e configuram a dificuldade fundamental nas tentativas de reunir elementos dos dois autores. (shrink)