1,721,025 research outputs found
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
Entanglement tracking and EPL entanglement generation in quantum networks using the discrete event simulator QNetSquid
No full textThe realisation of a quantum network in the near future has been made possible by the developments in qubit systems. Links between quantum nodes in major cities in The Netherlands are scheduled to be demonstrated by 2020. There are many things that need to be considered in the development of a quantum network, in this thesis a few of these will be examined. The first topic is entanglement generation using the EPL (Extreme Photon Loss) protocol in the presence of dephasing noise, which is an existing protocol. Novel contributions include the maximum achievable fidelities and entanglement generation rates, which are obtained using theoretical analysis and numerical simulations. Also for elementary states generated by the EPL protocol it is shown that doing distillation first and then an entanglement swap results in a roughly two times higher rate than the other way around. A new protocol called entanglement tracking is proposed to keep track of the classical information about entanglement in a quantum network. The entanglement tracker is a protocol that runs locally on every node in a quantum network and can communicate with the entanglement trackers of other nodes. The goal of the entanglement tracker is to keep a database with entanglement identifiers that is continuously updated after entanglement is modified. Performance metrics of an entanglement tracking protocol and a command interface with higher layer protocols are defined. We propose a format for entanglement identifiers and show how to update entanglement identifiers after an arbitrary number of entanglement swaps. The entanglement tracker is implemented in the discrete event simulator QNetSquid, which is under development by QuTech. It is applied by simulating a repeater chain using the entanglement tracking protocol, resulting in a completion time as a function of the number of repeaters. Future applications of the entanglement tracker are to assist routing of entanglement in a (large) quantum network, in which the tracker can take care of the classical communication.Applied Physic
Local multi-qubit Clifford equivalence of graph states
No full textIn the range of applications opened by quantum technology, often a highly entangled source state is needed as an input for a protocol (target state). The easiest example of such an application is QKD, other examples are quantum secret sharing and measurement based quantum computing. Generating a non-local entangled state is however not trivial. Let us assume that there is an entangled state (source state) present in the network before the start of the protocol. One can ask than whether this source state can be transformed to the target state with only local operations. Local operations usually have a lower error rate compared to non-local operations. As the set of all quantum states increases exponentially, we will restrict ourselves to graph states (quantum states described by a simple graph). This allows one to study the graphs and local operations in a graph theory perspective, instead of in a quantum information perspective. In this thesis we investigate the complexity of deciding equivalence of two graph states under local multi-qubit operations (T-LMQC-equivalent), where T refers to the partition denoting which qubits are on the same device which allows multi-qubit operations.When T consist only of single qubit nodes, this problem reduces to the single qubit Clifford equivalence problem (SQC-EQUIV). It is known that SQC-EQUIV can be solved in O(N^4). On the other side, if all qubits are in the same node, the problem can be solved in O(1) as every source state can be transformed to any graph state on the same vertex set. We will present three algorithms to solve T-LMQC equivalence. The first algorithm solves the problem in general but the running time scales exponentially in the number of multi-qubit nodes and the size of the graph. The other two scale polynomially in the size of the graph, but do not allow for nodes with more than 2 qubits. The remaining question is indeed whether deciding T-LMQC equivalence is an easy (in P) problem or a hard problem (NP-complete).Applied Physics | Quantum Technolog
Statistical analysis of the single-qubit unitarity randomized benchmarking protocol
No full textThis thesis provides an overview of the standard randomized benchmarking protocol, the extension to interleaved randomized benchmarking and the related unitarity randomized benchmarking, used to characterize noisy implementations of quantum gates from the Clifford group. It contains a brief overview of the textbook and literature preliminaries that are needed to understand the description and proof of these protocols. It outlines how previous work has reduced the number of random sequences needed in standard randomized benchmarking. Then it presents the new result of reduced number of sequences for unitarity randomized benchmarking and discusses the implication of these new results
Synchronized quantum network emulator using discrete event simulation
No full textComputer Science | Software Technolog
Verifiable hybrid secret sharing in the presence of noise
No full textVerifiable quantum secret sharing (VQSS) is the task of sharing a secret quantum state among the n nodes of a quantum network, in a way that it is possible to verify that the secret has been correctly distributed. A number of protocols that perform this task have been proposed. In particular, the verifiable hybrid secret sharing (VHSS) scheme proposed by Lipinska et al. (2019) realizes this task while reducing the number of required qubits, as compared to other existing protocols. The VHSS scheme was proven secure for noiseless quantum networks. In this work, we analyze its performance in the presence of noise. To do that, we first define different noise models in which qubits can be randomly erased or depolarized. Then, we propose several modifications for the protocol that allow us to run it more efficiently on quantum networks described by such noise models. Additionally, we explore a new approach to the VQSS task using approximate quantum error correction. We propose the verifiable trap secret sharing (VTSS) protocol, which combines the scheme by Lipinska et al. (2019) and the trap code by Broadbent et al. (2013). Our protocol achieves the same functionalities as the VHSS protocol and only requires that a strict majority of the nodes follows the protocol honestly, raising the maximum number of nodes that can cheat from ⌊(n-1)/4⌋ to ⌊(n-1)/2⌋. We can do this at the cost of increasing the probability of error in the protocol
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
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