1,720,958 research outputs found
Near-complete teleportation of a superposed coherent state
Full text link©2004 The American Physical Society
URL: http://link.aps.org/abstract/PRA/v70/e032327
doi:10.1103/PhysRevA.70.032327
PACS: 03.67.Hk, 03.65.Ud, 42.50.-pThe four Bell-type entangled coherent states, \alpha]\-alpha]+/-alpha]\alpha] and \alpha]\alpha]+/-\-alpha]\alpha], can be discriminated with a high probability using only linear optical means, as long as \alpha\ is not too small. Based on this observation, we propose a simple scheme to almost completely teleport a superposed coherent state. The nonunitary transformation that is required to complete the teleportation can be achieved by embedding the receiver's field state in a larger Hilbert space consisting of the field and a single atom and performing a unitary transformation on this Hilbert space.This research was supported by Korea Research Foundation Grant No. KRF-2002-070-C00029.We wish to thank Dr. J. Kim and Dr. B. A. Nguyen of KIAS and Professor M. S. Kim and Dr. H. Jeong of Queens University, Belfast for helpful discussions
Generalized measurement and conclusive teleportation with nonmaximal entanglement
No full text©2004 The American Physical Society
URL: http://link.aps.org/abstract/PRA/v70/e012309
doi:10.1103/PhysRevA.70.012309
PACS: 03.67.Mn, 03.67.Hk, 42.50.DvWe present linear optical schemes to perform generalized measurements for conclusive teleportation when the sender and the receiver share nonmaximal entanglement resulting from amplitude errors during propagation or generation. Three different cases are considered for which the states to be teleported are unknown superpositions of (a) single-photon and vacuum states, (b) vertically polarized and horizontally polarized photon states, and (c) two coherent states of opposite phases. The generalized measurement scheme for each case is analyzed, which indicates that the success probability is much more resistant to amplitude errors for case (c) than for case (a) or (b).This research was supported by Korea Research Foundation under Contract No. 2002-070-C00029
Robustness of multiparty nonlocality to local decoherence
No full text©2006 The American Physical Society
URL: http://link.aps.org/abstract/PRA/v74/e062112
doi:10.1103/PhysRevA.74.062112
PACS: 03.65.Ud, 03.65.YzWe investigate the robustness of multiparty nonlocality under local decoherence, acting independently and equally on each subsystem. To be specific, we consider an N-qubit Greenberger-Horne-Zeilinger (GHZ) state under a depolarization, dephasing, or dissipation channel, and examine nonlocality by testing violation of the Mermin-Klyshko inequality, which is one of Bell's inequalities for multiqubit systems. The results show that the robustness of nonlocality increases with the number of qubits, and that the nonlocality of an N-qubit GHZ state with even N is extremely persistent against dephasing.The authors thank Jinhyoung Lee for helpful discussions. S.S.J. and J.W.K. appreciate the financial support from the Korea Ministry of Information and Communication. H.W.L. was supported by the Ministry of Science and Technology (MOST) of Korea through the Leading Basic S&T Research Projects
Entanglement purification for high-dimensional multipartite systems
No full textWe propose an entanglement purification protocol for high-dimensional multipartite systems. In the protocol we can select a subensemble in a pure generalized Greenberger-Horne-Zeilinger (GHZ) state. This post-selection can be made by detecting the noise which contaminated the initial pure ensemble when the systems passed through a noisy environment. For the detection of noise we investigate the correlation properties of GHZ states and analyze their possible errors due to a noisy environment. We show that the protocol presented is more efficient than a simple generalization of the purification protocol for a bipartite state in high dimensions.This work was supported by MOST/KOSEF through the Quantum Photonic Science Research Center, the Leading Basic S&T Research Projects, and by the Korean Research Foundation Grant funded by the Korean Government (MOEHRD) (Grant No. KRF-2005-041-C00197). S.-W.L. was supported by the EU through the STREP project OLAQUI
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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