1,720,983 research outputs found
Quantum Communications: State Characterization and System Design
No full textQuantum information science is essential in the development of future-generation networks for a variety of new applications in the quantum domain involving sensing, cryptography, computing, and networking. The supremacy of quantum technologies relies on the exploitation of unique properties in quantum mechanics, such as superposition, entanglement, and indeterminacy. This calls for the design of communication systems and networks able to unleash the full potentialities of quantum mechanics.
The design of quantum communication systems and networks poses new challenges compared to classical ones. On the one side, at system level, the characterization of new classes of non-classical non-Gaussian states is needed for the design of innovative quantum communication systems with unprecedented performance. On the other side, at network level, the fragility of quantum systems requires the development of new methodologies for the analysis and the design of quantum networks.
The main objectives of this thesis are as follows: (i) characterize an important class of non-classical non-Gaussian states, namely photon-added coherent states (PACSs); (ii) establish the use of non-classical non-Gaussian states for quantum communication systems; and (iii) design a framework for the analysis of quantum key distribution (QKD) networks in the presence of a realistic intermittent relaying. It is shown that the use of non-classical non-Gaussian states can significantly improve the performance of quantum state discrimination. Moreover, it is also shown that a comprehensive analysis and the design of a QKD in the presence of intermittent relaying leads to new network design strategies. The findings of this thesis reveal the utility of non-classical non-Gaussian states for quantum communication systems and highlights the need for an holistic analysis of quantum networks.L’informazione quantistica sar`a essenziale nello sviluppo delle reti di futura generazione per una vasta gamma di applicazioni che coinvolgono, nel dominio quantistico, il sensing, la crittografia, la computazione, e le reti. La supremazia delle tecnologie quantistiche si basa sull’utilizzo delle proprietà peculiari della meccanica quantistica, tra cui la sovrapposizione di stati, l’entanglement e il principio di indeterminazione. Questo richiede quindi lo sviluppo di sistemi e reti di comunicazione in grado di sfruttare appieno le potenzialità della meccanica quantistica.
La progettazione di sistemi e reti di comunicazione quantistici pone nuove sfide rispetto alla controparte classica. Da un lato, a livello di sistema, è necessario caratterizzare nuove classi di stati non classici non Gaussiani per poter progettare sistemi di comunicazione quantistici innovativi, in grado di raggiungere nuovi livelli di prestazioni. Dall’altro lato, a livello di rete, la fragilità dei sistemi quantistici richiede lo sviluppo di nuove metodologie per l’analisi e la progettazione di reti quantistiche.
Gli obiettivi di questa tesi di dottorato sono: (i) caratterizzare una importante classe di stati non classici non Gaussiani, noti come photon-added coherent states (PACSs); (ii) introdurre l’utilizzo di stati non classici non Gaussiani nei sistemi di comunicazione quantistici; e (iii) sviluppare un framework per analizzare e progettare le reti per la distribuzione di chiavi quantistiche in presenza di relay intermittenti. Nella
tesi si dimostra che l’utilizzo di stati non classici non Gaussiani può migliorare significativamente la discriminazione di stati quantistici. Inoltre, si dimostra che un’analisi globale dei protocolli per la distribuzione di chiavi quantistiche porta a definire nuove strategie per il progetto delle reti. I risultati di questa tesi evidenziano l’utilità degli stati non classici non Gaussiani per i sistemi di comunicazione quantistici ed evidenziano la necessità di definire metodi olistici per l’analisi di reti quantistiche
Proof Nets for Classical Logic
No full textWe propose a new direct presentation of full (propositional) classical logic by means of proof nets, for which strong normalization and confluence hold true. Our proposal is based on the breaking of symmetry between propositional connectives, combined with a principle of focusing/defocusing
Computing with lambda-terms: A special issue dedicated to Corrado Böhm for his 90th birthday
Get PDFWe are very proud and honoured to dedicate this volume to Corrado Böhm, who has been for us a teacher, mentor, colleague, and friend. But most of all, he was a brilliant role-model to follow
Photon-varied quantum states: Unified characterization
No full textThis paper introduces photon-varied quantum states (PVQSs), which generalize the nonclassical states obtained via photon addition or subtraction operations. We provide a unified characterization of PVQSs in terms of characteristic function, quasiprobability distribution, Fock representation, and Mandel Q parameter. In the special case of photon-varied Gaussian states (PVGSs), the characteristic functions and the quasiprobability distributions are found to be in a simple canonical product structure. Necessary and sufficient conditions for the negativity of the quasiprobability distributions are also obtained for PVGSs. The unified characterization enables the design and analysis of quantum systems that exploit the non-Gaussian properties of PVQSs
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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