1,720,953 research outputs found
Multi-Qubit-Gatter in einem Quantencomputer mit gefangenen Ionen
No full textQuantencomputer versprechen Rechenprobleme effizienter zu lösen, als dies mit klassischen Computern je möglich wäre. Gefangene 171Yb+ -Ionen in einer linearen Paul-Falle, die einem Magnetfeldgradienten ausgesetzt sind, wurden bereits verwendet um Quantencomputing zu demonstrieren. Dabei werden die Qubits in Hyperfeinzuständen des elektronischen Grundzustands von 171Yb+ kodiert. Die Suszeptibilität der Qubit-Niveaus gegenüber Magnetfeldern durch einen linearen Zeeman-Effekt erzeugt die Kopplung der Qubits und ermöglicht außerdem eine individuelle Adressierung im Frequenzraum.
In einem Register von Ionen-Qubits, die in einer linearen Paul-Falle gespeichert sind, ist die durch den Magnetfeldgradienten erzeugte Kopplung eine inhärente "Alle-zu-Alle"-Kopplung. Die Implementierung eines bestimmten Quantenschaltkreises in einem Register von Ionen-Qubits erfordert die Abstimmung der Kopplungsstärke. In dieser Arbeit wird dies mit bis zu vier Qubits unter Verwendung einer gepulsten dynamischen Entkopplungssequenz erreicht, die die Qubits vor Dephasierung schützt, während die Kopplung gewählt werden kann. Die direkte Implementierung von Quantengattern mit drei oder mehr Qubits ist vorteilhaft, um das Potential eines Quantencomputers mit gefangenen Ionen voll auszuschöpfen. Ein Beispiel ist das hier implementierte Toffoli-Gatter. Ein treibendes Feld, das auf das Ziel-Qubit angewendet wird, wird verwendet, um eine Qubit-Rotation auf dem Ziel-Qubit in Abhängigkeit vom Zustand der Kontroll-Qubits durchzuführen. Um die Qubits während dieser Zeit vor Dephasierung zu schützen und die dauerhafteWechselwirkung der Qubits zu ermöglichen, wird eine dynamische Entkopplungssequenz angewendet und mit dem treibenden Feld auf dem Ziel-Qubit verschachtelt. Das Toffoli-Gatter wird dann eingesetzt, um einen Drei-Qubit- "Greenberger Horne Zeilinger"-Zustand und einen Halbaddierer zu realisieren. Halbaddierer, die als elementare Einheiten in der klassischen Informatik verwendet werden, bilden die Grundlage klassischer Rechenwerke. In einem Quantencomputer können sie mit Hilfe des hier vorgestellten Toffoli-Gatters und eines CNOT-Gatters realisiert werden.
Perzeptren sind als Teil künstlicher neuronaler Netze ein anderer Baustein der modernen Informatik. Im Rahmen dieser Arbeit wird ein Perzeptron-Gatter an einem Register aus drei Qubits demonstriert, wobei zwei Qubits als Steuerqubits und eines als Perzeptron dienen. Eine abstimmbare sigmoidale Anregung des Perzeptrons wird mittels eines adiabatischen Antriebsfeldes erzeugt, das mit einer dynamischen Entkopplungssequenz verschachtelt ist, um die Kohärenzzeiten zu verlängern und die Wechselwirkungsstärke zwischen den Qubits abzustimmen. Das Perzeptron wird dann in einem zweischichtigen neuronalen Netz eingesetzt, um eine XNOR-Operation zu implementieren.
Zusätzlich zur Anwendung als Qubit erlaubt die Abhängigkeit der Qubit-Resonanz vom Magnetfeld, ein Ionen-Qubit als Quantensensor für Magnetfelder und damit unter Nutzung eines Magnetfeldgradienten zur Messung von Kräften im 10^(−23) N-Bereich zu verwenden.Quantum computers promise to solve computational problems more efficiently than classical computers ever could. Trapped 171Yb+ ions in a linear Paul trap exposed to a magnetic field gradient have already been used to demonstrate quantum computing. The qubits are encoded in hyperfine states of the electronic ground state of 171Yb+ ions. The susceptibility of the qubit levels to magnetic fields by a linear Zeeman effect generates the coupling of the qubits and allows for individual addressing in frequency space.
In a register of qubits stored in a linear Paul trap, the coupling generated by the magnetic field gradient is an inherent all-to-all coupling. Implementing a given quantum circuit on a register of qubits requires tuning the coupling strength. Here tuning the coupling with up to four qubits is demonstrated using a pulsed dynamical decoupling sequence, which protects the qubits from dephasing while the coupling can be chosen.
Direct implementation of quantum gates with three or more qubits is necessary to exploit the full capabilities of a trapped-ion quantum computer. An example is the Toffoli gate implemented here. A driving field, applied to the target qubit, is used to perform a conditional rotation based on the control qubits state, while a dynamical decoupling sequence protects the coherence of the qubits. The Toffoli gate is then applied in a half-adder and is used to generate a three-qubit Greenberger Horne Zeilinger state.
Half-adders, which are used as elementary units in classical computer science, form the basis of classical arithmetic units. In a quantum computer, they can be realized using the Toffoli gate and a CNOT gate.
Perceptrons are a part of neural networks, a fundamental building block in modern computer science. Here a Perceptron gate is demonstrated on a register of three qubits where two qubits serve as control qubits and one as a perceptron. The characteristic tunable sigmoid excitation of the perceptron is shown using an adiabatic driving field interleaved with a dynamical decoupling sequence to prolong coherence times and tune the interaction strength between the qubits. The perceptron is then applied in a two-layer neural network to implement an XNOR operation.
In addition to its use as a qubit, the dependence of the qubit resonance on the magnetic field allows an ion qubit to be used as a quantum sensor for magnetic fields and thus, using a magnetic field gradient, to measure forces in the 10^(-23) N range
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
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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