1,720,953 research outputs found
Generation and fiber-based distribution of high-bandwidth entanglement for continuous variable quantum key distribution
No full textEntanglement is a key resource in many quantum information tasks, from quantum computing to quantum key distribution. In quantum key distribution in particular, use of entanglement enables protocols that are one-sided device independent. The source of its security are the inability to clone a quantum state as stated by the no-cloning theorem, as well as that the entanglement strength monotonically decreases if information is lost. The total decoherence experienced by the entangled state places an upper bound on the information an adversary could have gained while eavesdropping. Use of high bandwidth entangled states increases the key rate of such a protocol.
During this thesis I investigated the feasibility of distributing a continuous variable Einstein-Podolski-Rosen entangled state over a noisy channel for use in a one-sided device independent quantum key distribution protocol in an applied setting. To maximize the potential data rate I designed and set up two GHz bandwidth homodyne detectors as well as two GHz bandwidth monolithic squeezed light sources which constituted the entanglement source. The squeezed light sources individually produced states exhibiting a noise reduction of up to 6.5 dB compared to shot noise at 30 MHz and 2.9 dB at a frequency above 1 GHz. By combining the two squeezed states I produced an entangled state that showed a 4.2 dB reduced variance relative to the combined shot noise of the measured light. This allowed to infer a violation of the EPR-Reid criterion. I distributed the entangled state between two separate buildings on campus via a 1 km long optical fiber link. Transmitting one part of the entangled state through the fiber link, the entanglement showed little degradation. The peak relative noise reduction remained at up to 3.7 dB below the combined shot noise over a 10 MHz wide frequency band. I used this band to generate a raw key pair at 336 kbit s^−1. Additionally, a 250 MHz wide frequency band remained free of other noise sources at more than 2.0 dB below combined shot noise. Improving the initial squeezing factor of both sources can extend the violation of the EPR-Reid criterion to this band, enabling its use for key generation and thus increasing the key rate.
This result demonstrates the viability of a continuous variable quantum key distribution protocol based on two-mode squeezed states in the presence of typical environmental noise sources. Stabilizing the readout quadrature would further increase the raw key rate to 50 Mbit s^−1.Verschränkung bildet eine der zentralen Resourcen der Quanteninformation, mit Anwendungen in Quantencomputern und Quantenschlüsselverteilung. Besonders in der Quantenschlüsselverteilung ermöglicht der Einsatz von Verschränkung einseitig geräteunabhängige Protokolle. Ursprung dieser erhöhten Sicherheit ist, dass die Stärke der Verschränkung monoton mit Informationsverlust abnimmt, sowie das No-Cloning Theorem, welches es verbietet eine exakte Kopie eines beliebigen Quantenzustands zu erzeugen. Die Gesamtdekohärenz der verschränkten Zustände setzt eine obere Grenze für die Information, die bei einem Abhörversuch erlangt worden sein kann. Die Schlüsselrate dieser Protokolle skaliert dabei mit der Bandbreite der Verschränkung.
In dieser Doktorarbeit untersuchte ich die Realisierbarkeit der Verteilung eines Einstein-Podolski-Rosen verschränkten Zustands über einen realen rauschbehafteten Kanal. Der explizite Schwerpunkt lag auf der Verwendung der Zustands in einem einseitig geräteunabhängigen Quantenschlüsselverteilungsprotokol. In dieser Zeit entwarf ich zwei Quetschlichtquellen, die den verschränkten Zustand erzeugten, sowie zwei Homodyndetektoren, um diesen zu vermessen. Dabei wählte ich die Bandbreite von Lichtquellen und Detektoren im GHz Bereich, um die erreichbare Schlüsselrate zu maximieren. Einzeln vermessen produzierten die Quetschlichtquellen Zustände mit einem reduzierten Quantenrauschen von bis zu 6.5 dB unter dem Schrotrauschen bei 30 MHz Seitenbandfrequenz, sowie eine Reduktion von 2.9 dB über 1 GHz Seitenbandfrequenz. Durch Überlagerung der beiden gequetschten Zustände erzeugte ich einen verschränkter Zustand, der eine Varianz von 4.2 dB unter dem kombinierten Schrotrauschen des gemessenen Lichts erreichte. Daraus konnte ich eine Veletzung des EPR-Reid Kriteriums ableiten. Den verschränkte Zustand verteilte ich zwischen zwei unterschiedlichen Gebäuden auf dem Campus mittels einer 1 km langen optischen Glasfaser. Nach der Transmission durch die Faser sank der Spitzenwert auf 3.7 dB, gemessen über ein 10 MHz breites Frequenzband. Dieses Frequenzband nutzte ich, um einen Rohschlüssel mit einer Rohschlüsselrate von 336 kbit s^−1 zu generieren. Ein weiteres 250 MHz breites Frequenzband zeigte eine Varianz von mehr als 2.0 dB unter dem kombinierten Schrotrauschen. Ein höherer initialer Quetschfaktor kann eine Verletzung des EPR-Reid Kriterium in diesem Frequenzband ermöglichen. Dies würde das Frequenzband zusätzlich für die Schlüsselgenerierung eröffnen und so die Schlüsselrate zu erhöhen.
Die Ergebnisse dieser Arbeit demonstrieren die Umsetzbarkeit eines Quantenschlüsselverteilungsprotokolls basierend auf Zwei-Moden gequetschten Zuständen in einer verrauschten Umgebung. Durch Stabilisierung der Auslesequadratur kann die Rohschlüsselrate weiter auf bis zu 50 Mbit s^−1 erhöht werden
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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