Twin inequality for fully contextual quantum correlations

Quantum mechanics exhibits a very peculiar form of contextuality. Identifying and connecting the simplest scenarios in which more general theories can or cannot be more contextual than quantum mechanics is a fundamental step in the quest for the principle that singles out quantum contextuality. The former scenario corresponds to the Klyachko-Can-Binicioglu-Shumovsky (KCBS) inequality. Here we show that there is a simple tight inequality, twin to the KCBS, for which quantum contextuality cannot be outperformed. In a sense, this twin inequality is the simplest tool for recognizing fully contextual quantum correlations.Comment: REVTeX4, 4 pages, 1 figur

Bell's theorem without inequalities and without unspeakable information

A proof of Bell's theorem without inequalities is presented in which distant local setups do not need to be aligned, since the required perfect correlations are achieved for any local rotation of the local setups.Comment: REVTeX4, 4 pages, 1 figure; for Asher Peres' Festschrift, to be published in Found. Phy

La crisis modernista y la encíclica Pascendi en la novela Jean Barois (de R. Martin du Gard)

La novela Jean Barois, del premio Nobel Roger Martin du Gard, refleja en sus páginas algunas de las controversias más importantes de la crisis modernista: los dogmas como simples símbolos de los valores religiosos; el conflicto entre ciencia y fe; el positivismo histórico y los problemas que plantea a la existencia de una revelación objetiva; la experiencia y el sentimiento religiosos. Para su autor, discípulo del modernista Marcel Hébert, la raíz intelectual de esta crisis teológica coincide con la que Pío X señala en Pascendi: el agnosticismo filosófico e histórico, que encierra la fe en el dominio del sentimiento, de lo subjetivo y relativo

State-independent quantum violation of noncontextuality in four dimensional space using five observables and two settings

Recently, a striking experimental demonstration [G. Kirchmair \emph{et al.}, Nature, \textbf{460}, 494(2009)] of the state-independent quantum mechanical violation of non-contextual realist models has been reported for any two-qubit state using suitable choices of \emph{nine} product observables and \emph{six} different measurement setups. In this report, a considerable simplification of such a demonstration is achieved by formulating a scheme that requires only \emph{five} product observables and \emph{two} different measurement setups. It is also pointed out that the relevant empirical data already available in the experiment by Kirchmair \emph{et al.} corroborate the violation of the NCR models in accordance with our proof

Decoherence-Free Quantum Information Processing with Four-Photon Entangled States

Decoherence-free states protect quantum information from collective noise, the predominant cause of decoherence in current implementations of quantum communication and computation. Here we demonstrate that spontaneous parametric down-conversion can be used to generate four-photon states which enable the encoding of one qubit in a decoherence-free subspace. The immunity against noise is verified by quantum state tomography of the encoded qubit. We show that particular states of the encoded qubit can be distinguished by local measurements on the four photons only.Comment: 4 pages, 4 eps figures, revtex

CO and trans-cinnamaldehyde as corrosion inhibitors of I825, L80-13Cr and N80 alloys in concentrated HCl solutions at high pressure and temperature

Peer reviewedPostprin

Proposed experiment for the quantum "Guess my number" protocol

An experimental realization of the entanglement-assisted "Guess my number" protocol for the reduction of communication complexity, introduced by Steane and van Dam, would require producing and detecting three-qubit GHZ states with an efficiency eta > 0.70, which would require single photon detectors of efficiency sigma > 0.89. We propose a modification of the protocol which can be translated into a real experiment using present-day technology. In the proposed experiment, the quantum reduction of the multi-party communication complexity would require an efficiency eta > 0.05, achievable with detectors of sigma > 0.47, for four parties, and eta > 0.17 (sigma > 0.55) for three parties.Comment: REVTeX4, 4 pages, 1 figur

Multi-level, multi-party singlets as ground states and their role in entanglement distribution

We show that a singlet of many multi-level quantum systems arises naturally as the ground state of a physically-motivated Hamiltonian. The Hamiltonian simply exchanges the states of nearest-neighbours in some network of qudits (d-level systems); the results are independent of the strength of the couplings or the network's topology. We show that local measurements on some of these qudits project the unmeasured qudits onto a smaller singlet, regardless of the choice of measurement basis at each measurement. It follows that the entanglement is highly persistent, and that through local measurements, a large amount of entanglement may be established between spatially-separated parties for subsequent use in distributed quantum computation.Comment: Corrected method for physical preparatio

Semicentral idempotents in the multiplication ring of a centrally closed prime ring

Let R be a ring and let M(R) stand for the multiplication ring of R. An idempotent E in M(R) is called left semicentral if its range E(R) is a right ideal of R. In the case that R is prime and centrally closed we give a description of the left semicentral idempotents in M(R). As an application we prove that, if, in addition, M(R) is Baer (respectively, regular or Rickart), then R is Baer (respectively, regular or Rickart). Similar results for *-rings are also proved.• Ministerio de Ciencia, Innovación y Universidades de España y Fondos FEDER: Proyecto MTM2009-12067 • Junta de Andalucía: Proyecto FQM290peerReviewe

Modelo Biomecánico de la técnica individual del servicio del tenis

El servicio es un golpe fundamental en el resultado de un partido. Se han analizado biomecánicamente los primeros servicios de jugadoras de alto nivel, mediante la fotogrametría 3D. El análisis de la cadena cinética de ambas muestran correlaciones significativas en la transferencia de energía entre los diferentes segmentos. Los modelos biomecánicos hallados muestran matemáticamente como los servicios de ambas jugadoras siguen un patrón determinado, pudiéndose predecir los servicios «buenos» y «malos de las jugadoras. Ambos modelos son diferentes entre sí