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Sökning: WFRF:(Cabello Adán)

  • Resultat 11-20 av 46
  • Föregående 1[2]345Nästa
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11.
  • Araujo, Mateus, et al. (författare)
  • Tests of bell inequality with arbitrarily low photodetection efficiency and homodyne measurements
  • 2012
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 86:3, s. 030101-
  • Tidskriftsartikel (refereegranskat)abstract
    • We show that hybrid local measurements combining homodyne measurements and photodetection provide violations of a Bell inequality with arbitrarily low photodetection efficiency. This is shown in two different scenarios: when one part receives an atom entangled to the field mode to be measured by the other part and when both parts make similar photonic measurements. Our findings promote the hybrid measurement scenario as a candidate for loophole-free Bell tests beyond previous expectations.
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12.
  • Bengtsson, Ingemar (författare)
  • A Kochen-Specker inequality for a SIC
  • 2012
  • Ingår i: ; 376:4, s. 374-376
  • Tidskriftsartikel (refereegranskat)abstract
    • Yu and Oh (eprint) [1] have given a state-independent proof of the Kochen–Specker theorem in three dimensions using only 13 rays. The proof consists of showing that a non-contextual hidden variable theory necessarily leads to an inequality that is violated by quantum mechanics. We give a similar proof making use of 21 rays that constitute aSIC (symmetric informationally-complete positive operator-valued measure) and a complete set of MUB (mutually unbiased bases). A theory-independent inequality is also presented using the same 21 rays, as required for experimental tests of contextuality.
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13.
  • Bengtsson, Ingemar, et al. (författare)
  • Pentagrams and paradoxes
  • 2011
  • Ingår i: ; 41, s. 414-
  • Tidskriftsartikel (refereegranskat)
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14.
  • Bengtsson, Ingemar (författare)
  • Universality of State-Independent Violation of Correlation Inequalities for Non-Contextual Theories
  • 2009
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:5, s. 050401-
  • Tidskriftsartikel (refereegranskat)abstract
    • We show that the state-independent violation of inequalities for noncontextual hidden variable theories introduced in [Phys. Rev. Lett. 101, 210401 (2008)] is universal, i.e., occurs for any quantum mechanical system in which noncontextuality is meaningful. We describe a method to obtain state-independent violations for any system of dimension d >= 3. This universality proves that, according to quantum mechanics, there are no "classical'' states.
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15.
  • Budroni, Costantino, et al. (författare)
  • Bell inequalities from variable-elimination methods
  • 2012
  • Ingår i: Journal of Physics A. - 1751-8113 .- 1751-8121. ; 45:38, s. 385304-
  • Tidskriftsartikel (refereegranskat)abstract
    • Tight Bell inequalities are facets of Pitowsky's correlation polytope and are usually obtained from its extreme points by solving the hull problem. Here, we present an alternative method based on a combination of algebraic results on extensions of measures and variable-elimination methods, e. g., the Fourier-Motzkin method. Our method is shown to overcome some of the computational difficulties associated with the hull problem in some non-trivial cases. Moreover, it provides an explanation for the arising of only a finite number of families of Bell inequalities in measurement scenarios where one experimenter can choose between an arbitrary number of different measurements.
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17.
  • Cabello, Adan, et al. (författare)
  • Hybrid ququart-encoded quantum cryptography protected by Kochen-Specker contextuality
  • 2011
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 84:3, s. 030302-
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantum cryptographic protocols based on complementarity are not secure against attacks in which complementarity is imitated with classical resources. The Kochen-Specker (KS) theorem provides protection against these attacks, without requiring entanglement or spatially separated composite systems. We analyze the maximum tolerated noise to guarantee the security of a KS-protected cryptographic scheme against these attacks and describe a photonic realization of this scheme using hybrid ququarts defined by the polarization and orbital angular momentum of single photons.
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18.
  • Cabello, Adan, et al. (författare)
  • Loophole-Free Bell Test Based on Local Precertification of Photon's Presence
  • 2012
  • Ingår i: PHYSICAL REVIEW X. - 2160-3308. ; 2:2, s. 021010-
  • Tidskriftsartikel (refereegranskat)abstract
    • A loophole-free violation of Bell inequalities is of fundamental importance for demonstrating quantum nonlocality and long-distance device-independent secure communication. However, transmission losses represent a fundamental limitation for photonic loophole-free Bell tests. A local precertification of the presence of the photons immediately before the local measurements may solve this problem. We show that local precertification is feasible by integrating three current technologies: (i) enhanced single-photon down-conversion to locally create a flag photon, (ii) nanowire-based superconducting single-photon detectors for a fast flag detection, and (iii) superconducting transition-edge sensors to close the detection loophole. We carry out a precise space-time analysis of the proposed scheme, showing its viability and feasibility.
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19.
  • Cabello, Adan, et al. (författare)
  • Minimum Detection Efficiency for a Loophole-Free Atom-Photon Bell Experiment
  • 2007
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 98, s. 220402-1-220402-4
  • Tidskriftsartikel (refereegranskat)abstract
    • In Bell experiments, one problem is to achieve high enough photodetection to ensure that there is no possibility of describing the results via a local hidden-variable model. Using the Clauser-Horne inequality and a two-photon nonmaximally entangled state, a photodetection efficiency higher than 0.67 is necessary. Here we discuss atom-photon Bell experiments. We show that, assuming perfect detection efficiency of the atom, it is possible to perform a loophole-free atom-photon Bell experiment whenever the photodetection efficiency exceeds 0.50.
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20.
  • Cabello, Adan, et al. (författare)
  • Minimum detection efficiency required for a loophole-free violation of the Braunstein-Caves chained Bell inequalities
  • 2009
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 79:6, s. 062109-1-062109-7
  • Tidskriftsartikel (refereegranskat)abstract
    • The chained Bell inequalities of Braunstein and Caves involving N settings per observer have some interesting applications. Here we obtain the minimum detection efficiency required for a loophole-free violation of the Braunstein-Caves inequalities for any N greater than= 2. We discuss both the case in which both particles are detected with the same efficiency and the case in which the particles are detected with different efficiencies.
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  • Resultat 11-20 av 46
  • Föregående 1[2]345Nästa
 
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