19 research outputs found

    Entanglement of an impurity and conduction spins in the Kondo model

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    Based on Yosida's ground state of the single-impurity Kondo Hamiltonian, we study three kinds of entanglement between an impurity and conduction electron spins. First, it is shown that the impurity spin is maximally entangled with all the conduction electrons. Second, a two-spin density matrix of the impurity spin and one conduction electron spin is given by a Werner state. We find that the impurity spin is not entangled with one conduction electron spin even within the Kondo screening length ξK\xi_K, although there is the spin-spin correlation between them. Third, we show the density matrix of two conduction electron spins is nearly same to that of a free electron gas. The single impurity does not change the entanglement structure of the conduction electrons in contrast to the dramatic change in electrical resistance.Comment: 5 pages, 2 figures, accepted for publication in Physical Review

    Entanglement criteria via the uncertainty relations in su(2) and su(1,1) algebra: detection of non-Gaussian entangled states

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    We derive a class of inequalities, from the uncertainty relations of the SU(1,1) and the SU(2) algebra in conjunction with partial transposition, that must be satisfied by any separable two-mode states. These inequalities are presented in terms of the su(2) operators J_x, J_y, and the total photon number N_a+N_b. They include as special cases the inequality derived by Hillery and Zubairy [Phys. Rev. Lett. 96, 050503 (2006)], and the one by Agarwal and Biswas [New J. Phys. 7, 211 (2005)]. In particular, optimization over the whole inequalities leads to the criterion obtained by Agarwal and Biswas. We show that this optimal criterion can detect entanglement for a broad class of non-Gaussian entangled states, i.e., the su(2) minimum-uncertainty states. Experimental schemes to test the optimal criterion are also discussed, especially the one using linear optical devices and photodetectors.Comment: published version, presentation polished with references added, 7 pages, 4 figure

    Design and Comparison of Immersive Interactive Learning and Instructional Techniques for 3D Virtual Laboratories

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    This work presents the design, development, and testing of 3D virtual laboratories for practice, specifically in undergraduate mechanical engineering laboratories. The 3D virtual laboratories, implemented under two virtual environments3DTV and Computer Automated Virtual Environment (CAVE)serve as pre-lab sessions performed before the actual physical laboratory experiment. The current study compares the influence of two instructional methods (conventional lecture-based and inquiry-based) under two virtual environments, and the results are compared with the pre-lab sessions using a traditional paper-based lab manual. Subsequently, the evaluation is done by conducting performance and quantitative assessments from students pre-and post-laboratory performances. The research results demonstrate that students in the virtual modules (3DTV and CAVE) performed significantly better in the actual physical experiment than the students in the control group in terms of the overall experiment familiarity and procedure and the conceptual knowledge associated with the experiment. 2015 by the Massachusetts Institute of Technology

    Shor-Preskill Type Security-Proofs for Concatenated Bennett-Brassard 1984 Quantum Key Distribution Protocol

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    We discuss long code problems in the Bennett-Brassard 1984 (BB84) quantum key distribution protocol and describe how they can be overcome by concatenation of the protocol. Observing that concatenated modified Lo-Chau protocol finally reduces to the concatenated BB84 protocol, we give the unconditional security of the concatenated BB84 protocol.Comment: 4 pages, RevTe

    Quantum Teleportation and Bell's Inequality Using Single-Particle Entanglement

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    A single-particle entangled state can be generated by illuminating a beam splitter with a single photon. Quantum teleportation utilizing such a single-particle entangled state can be successfully achieved with a simple setup consisting only of linear optical devices such as beam splitters and phase shifters. Application of the locality assumption to a single-particle entangled state leads to Bell's inequality, a violation of which signifies the nonlocal nature of a single particle.Comment: 7 pages including 3 figures in eps-forma

    Light-Gravitino Production at Hadron Colliders

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    We consider the production of gravitinos (G~\widetilde G) in association with gluinos (g~\tilde g) or squarks (q~\tilde q) at hadron colliders, including the three main sub-processes: qqˉ−>g~G~q \bar q -> \tilde g\widetilde G, qg−>q~G~qg -> \tilde q\widetilde G, and gg−>g~G~gg -> \tilde g\widetilde G. These channels become enhanced to the point of being observable for sufficiently light gravitino masses (mG~<10−4eVm_{\widetilde G} < 10^{-4} eV), as motivated by some supersymmetric explanations of the CDF eeγγ+ET,missee\gamma\gamma+ E_{T,miss} event. The characteristic signal of such events would be monojets, as opposed to dijets obtained in the more traditional supersymmetric process ppˉ−>g~g~p \bar p -> \tilde g\tilde g. Searches for such events at the Tevatron can impose lower limits on the gravitino mass. In the Appendix, we provide a complete set of Feynman rules for gravitino interactions used in our calculation.Comment: 25 pages, including 8 figures. Typeset in LaTex2e. Replaced with corrected figures, and some minor rewrite

    COLLECTIVE REMOTE STATE PREPARATION

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    Single-photon characteristics of superposed weak coherent states

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