955 research outputs found
Geometrically-controlled polarisation processing in femtosecond-laser-written photonic circuits
No full textAbstractPolarisation of light is a powerful and widely used degree of freedom to encode information, both in classical and quantum applications. In particular, quantum information technologies based on photons are being revolutionised by the use of integrated photonic circuits. It is therefore very important to be able to manipulate the polarisation of photons in such circuits. We experimentally demonstrate the fabrication by femtosecond laser micromachining of components such as polarisation insensitive and polarising directional couplers, operating at 1550 nm wavelength, where the two opposite behaviours are achieved just by controlling the geometric layout of the photonic circuits, being the waveguides fabricated with the same irradiation recipe. We expect to employ this approach in complex integrated photonic devices, capable of a full control of the photons polarisation for quantum cryptography, quantum computation and quantum teleportation experiments.</jats:p
A Modular Logic Approach for Expressing Web Services in XML Applying Dynamic Rules in XML
No full textRuleML is considered to be a markup language for the semantic web. It allows the enrichment of web ontologies by adding definitions of derived concepts and it enhances interoperability among different systems and tools by publishing rules in an XML format. Moreover the in-creasing demand for interfaces that enhance information sharing has given rise to XML doc-uments that include embedded calls to web services. In this paper we propose a variation of RuleML that is based on modular logic programming. Our approach is based in a two level architecture. In the first level a modular logic language, called M-log, is presented. This lan-guage encompasses several mechanisms for invoking web services. In the second level we ex-ploit the semantics of M-log to present a variation of RuleML with rich modeling capabilities. Formal foundations for this variation are given through direct translation to M-log semantics.Knowledge Management, XML, Modular Logic Programming, E-Services
Symmetric polarization-insensitive directional couplers fabricated by femtosecond laser writing
No full textWe study analytically the polarization behaviour of directional couplers composed of birefringent waveguides, showing that they can induce polarization transformations that depend on the specific input-output path considered. On the basis of this study, we propose and demonstrate experimentally, by femtosecond laser writing, directional couplers that yield a polarization-independent power splitting and, at the same time, preserve the polarization state of the propagating light. More in detail, we devise two di erent approaches to realize such devices: the first one is based on local birefringence engineering by additional refractive index modification tracks, while the second one exploits ultra-low birefringence waveguides (b = 1.2 × 10−6), obtained by thermal annealing
Ioannis Dallaei De imaginibus libri IV.
No full textIncludes errata at end.Signatures: *⁸ A-2L⁸ 2M⁴ chi².Woodcut printer's device on t.p. Head- and tail-pieces, initials.Scanned copy bound with: Joannis Dallaei Apologia pro ecclesiis reformatis. Amstelodami : Apud Jodocum Jansonium, 1652.Mode of access: Internet.Binding: vellum. Author & titles written at head of spine.With his: Apologia pro ecclesiis reformatis (Amsterdam : J. Janson, 1652)
Integrated quantum photonic simulators fabricated by femtosecond laser micromachining
No full textLe tecnologie che sfruttano le proprietà della meccanica quantistica possono essere considerate il prossimo passo più significativo nell'evoluzione della scienza dell'informazione e delle telecomunicazioni, considerando che quello precedente è stato lo sviluppo dei micro-transistor e delle comunicazioni wireless (senza fili). Teoricamente, persino i computer quantistici di piccole dimensioni potrebbero superare, in quanto a prestazioni, i più grandi e potenti supercomputer, così come le telecomunicazioni quantistiche potrebbero consentire, in modo assolutamente sicuro, nonché senza il minimo rischio di perdita, lo scambio ultra-veloce di informazioni, perfino sulle più lunghe distanze. Naturalmente, l'importanza di tali tecnologie ha comportato negli ultimi due decenni un grande impiego, da parte di istituzioni sia pubbliche che private, di risorse nel campo della ricerca e dello sviluppo, dando adito ad importantissimi sviluppi tecnologici e scoperte scientifiche.
Tuttavia, ad oggi nessuna di queste tecnologie è stata dimostrata su una piattaforma completa, autonoma e puramente quantistica. Questo in parte poiché la natura quantistica del mondo non è stata ancora compresa appieno ed i suoi principi basilari insinuano il dubbio nella comunità scientifica; in parte poiché le tecnologie odierne non sono in grado di supportare complicati processi quantistici. Una soluzione per entrambe le suddette questioni è stata proposta per essere messa in atto da simulatori, in grado di simulare o performare semplici imput quantistici, utilizzando così una piattaforma che potrebbe potenzialmente far intuire meglio la natura della teoria quantistica, ed allo stesso tempo dimostrerebbe il potenziale delle applicazioni quantistiche.
In questa tesi, il femtosecond laser micromachining è stato utilizzato per realizzare circuiti fotonici integrati, che permettono di propagare, controllare e modificare singoli fotoni, in substrati di vetro. Questa tecnologia permette di sviluppare in maniera semplice complicati strumenti ottici, i simulatori quantici, designati all'emulazione di processi quantici attraverso l'uso di singoli fotoni. In particolare, questo esperimento, che è la dimostrazione di una vera e propria simulazione fotonica quantistica, ha permesso per la prima volta di raggiungere l'obiettivo di simulare l'evoluzione di multiple eccitazioni in una catena di spin ("catena di rotazione"). Un esperimento che testa la proprietà fondamentale del quanto nel contesto della fisica quantistica, dimostrando l'importanza della piattaforma nell'indagine dei fondamentali concetti della fisica. Inoltre, è stato condotto con successo un esperimento sullo sviluppo di un set completo di componenti integrate di processi di polarizzazione per la lunghezza d'onda delle telecomunicazioni. Ed infine sono stati raggiunti significanti miglioramenti nel processo della fabbricazione, permettendo la realizzazione di waveguide arrays ("schieramenti d'onda") per i percorsi di quanti multiparticellari.Technologies that exploit the properties of quantum mechanics are suggested that will be the next major step in the evolution of information science and telecommunications, considering that the previous was the development of the micro-transistor and wireless communications. Characteristically, it is theoretically true that even small scale quantum computers could outperform the largest most powerful modern supercomputers, while quantum telecommunications could enable ultra fast, absolutely secure information exchange without loss of information even at very long distances. The importance of these technologies has naturally led public and private institutions to invest a lot of effort in research and development, especially the past two decades, and has lead to great technological developments and scientific breakthroughs.
Nevertheless, to this date, none of these technologies has been demonstrated in a complete, autonomous and purely quantistic platform. Part of this is be- cause the quantum nature of the world is still not well understood, and basic principles are still puzzling the scientific community, and another part of it is because the current technologies are not capable to carry out efficiently complicated quantum processes. An intermediate solution to both these issues, has been suggested to be provided by quantum simulators, which are systems capable to perform or simulate simple quantum tasks; thus providing a platform that could potentially give better insight to the nature of quantum theory, and on the same time showcase the potential of quantum applications.
In this thesis, femtosecond laser micromachining is employed in order to realise integrated photonic circuits, that allow to propagate, control and manipulate individual photons, in glass substrates. This technology, allows to develop in a simple manner, complicated optical apparatuses that are designed to emulate quantum processes using single photons. Effectively therefore, they are photonic quantum simulators. In this work particularly, the simulation of the evolution of multiple excitations in a spin chain is achieved for the first time, in an experiment that is a demonstration of a proper photonic quantum simulation. An experiment that tests the fundamental quantum property of quantum contextuality is per- formed, showing the potential of the platform to investigate fundamental physical concepts. Additionally, work on the development of a complete set of polarisation processing integrated components for the telecommunication wavelength has been conducted successfully, and also significant improvements on the fabrication process have been achieved allowing the realisation of larger waveguide arrays for multi-particle quantum walks.DIPARTIMENTO DI FISICALaser Physics, Photonic devices and applications29RAMPONI, ROBERTATARONI, PAOL
Ioannis Metaxas: Speech on the occasion of the inauguration of public works
No full textTitle: Λόγος κατά τα εγκαίνια των έργων του Σελινούντος Αιγιαλείας (Speech on the occasion of the inauguration of the public works at Selinous, Egialia) Originally published: Delivered at Selinous on 31 October 1937. Language: Greek The excerpts used are from Ioannis Metaxas, Λόγοι και Ομιλίες (Athens: Ερμής, 1992), pp. 247–255. About the author Ioannis Metaxas [1871, Ithaca (Ionian Islands)–1941, Athens]: military officer and politician. He was born into a well-known aristocratic family. In ..
Literary Recants of a Tenth-Century Scholar: The Case of Ioannis Kaminiates
No full textThis paper seeks to interpret the attitude of Ioannis Kaminiates towards Homer, for while initially criticising his literary predecessor, the author of On the Capture of Thessaloniki later adopts many of his turns of phrase
My journey
No full textTitle: Τό ταξίδι μου (My journey) Originally published: Αθήνα, n. p., 1888 Language: Greek The excerpts used are from Ἰωάννης Ψυχάρης, Τό ταξίδι μου, ed. by Alkis Agelou (Athens: Ἐστία: Νεοελληνική Βιβλιοθήκη, 1993), pp. 37–39, 64–67, 75–76, 89. About the author Ioannis (Jean) Psicharis [1854, Odessa – 1929, Paris]: writer, linguist and critic. Psicharis was born to a well-off family. After his mother’s early death his father brought him to Istanbul in 1860, where he spent his childhood. His ..
Of this great idea
No full textTitle: Τῆς Μεγάλης αυτής Ἰδέας (Of this Great Idea) Originally published: Ιt was published in Ἠ τῆς τρίτης Σεπτεµβρίου ἐν Άθήναις Ἐθνική Συνέλευσις, Athens, Βουλή των Ελλήνων, 1844 Language: Greek The excerpts used are from Constantinos Th. Dimaras, Ελληνικός Ρωµαντισµός (Athens: Ερµής, 1985), pp. 405–406. About the author Ioannis Kolettis [1773, Sirako (Epirus) – 1847, Athens]: medical doctor, politician and writer. He was educated in his hometown of Sirako and in nearby Kalarites, both pros..
Gramática, traducción y lengua en Ioannis Vilarás (1771-1823)
No full textThe author presents in this article Velaras’s brief treatise The Romeic Language, Corfu, 1814, a key guide on the vindication of spoken Greek. His linguistic proposals, as well as the stylistic and translation decisions of the author are succinctly analyzed and commented on in order to defend its importance for Greek studies.La autora presenta en este artículo el opúsculo de Ioannis Vilarás, La lengua romeica, Corfú, 1814, obra de referencia sobre la defensa de la lengua griega hablada. Se analizan sucintamente las propuestas lingüísticas, estilísticas y traductoras del autor que se desprenden de esta obra así como su trascendencia en las letras neogriegas
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