Photon-number resolving detector based on a series array of superconducting nanowires

We present the experimental demonstration of a superconducting photon number resolving detector. It is based on the series connection of N superconducting nanowires, each connected in parallel to an integrated resistor. The device provides a single voltage readout, proportional to the number of photons absorbed in distinct nanowires. Clearly separated output levels corresponding to the detection of n=1-4 photons are observed in a 4-element detector fabricated from an NbN film on GaAs substrate, with a single-photon system quantum efficiency of 2.6% at the wavelength of 1300nm. The series-nanowire structure is promising in view of its scalability to large photon numbers and high efficiencies.Comment: 12 pages, 6 figure

Gestione di un data lake strutturato attraverso il riconoscimento semantico dei dati acquisiti

Negli ultimi anni si è assistito ad un incremento smisurato nella generazione di dati che ha dato vita al fenomeno dei Big Data. Le caratteristiche attribuite a questi dati hanno evidenziato la necessità di riorganizzare i processi aziendali e di sviluppare nuove soluzioni che permettessero di cogliere le opportunità dei Big Data e di controllare la complessità derivante dalla loro gestione. Per rispondere a quest'esigenza ci si è rivolti all'utilizzo di framework basati su architetture parallele ma, senza definire un'organizzazione interna al Data Lake (repository in cui i dati vengono memorizzati) ed adeguate politiche di governance, abilitate da una solida base di metadati, c'è il rischio che il valore dei dati vada perdendosi e che i dati diventino difficilmente reperibili all'interno del repository. Il prototipo di tesi è basato su un caso di studio aziendale ed è volto a predisporre i sistemi aziendali ad una corretta gestione futura dei Big Data. Il suo obiettivo è sviluppare un approccio estendibile e parametrizzabile che permetta di indicizzare, nella maniera più automatica possibile, i singoli file presenti nel Data Lake sulla base del loro tipo di evento tramite l'estrazione di metadati strutturali, di processo e semantici, che consentano e facilitino il recupero dei file quando rilevanti rispetto a determinate interrogazioni. I file che il caso di studio prende in esame sono file XML che fanno riferimento ad eventi generati in ambito sanitario. Per portare a termine quest'obiettivo viene definita un'architettura per Data Lake ed un modello per l'archiviazione di metadati, realizzato come ontologia. Le funzionalità del prototipo, come tarare i parametri del processo di estrazione e visualizzare i risultati, sono disponibili tramite un'interfaccia web

Progettazione e sviluppo di un sistema software per il ticketing

La presente tesi esamina la progettazione e lo sviluppo di un sistema software la cui funzionalità principale è quella di gestire segnalazioni in merito a problematiche riscontrate dall'utente che possono riguardare diversi ambiti come segnalazioni post-vendita in merito a progetti informatici (bug, mancanza di funzionalità, errori di funzionalità...) o segnalazioni in merito a disguidi su ordini (ordine errato, ordine non ricevuto...). Tali problematiche vengono identificate nel ticket. Una volta aperto, dopo un'analisi del problema, il ticket viene assegnato ad un operatore che si occuperà di risolverlo. In questa fase operatore ed utente possono scambiarsi informazioni aggiuntive tramite un thread di conversazione associato al ticket. Il sistema è volto ad uniformare il canale di comunicazione tra azienda e cliente e a fornire all'azienda che ne ha fatto richiesta un sistema efficiente per la gestione di queste segnalazioni, portando dei benefici ad entrambe le parti, impiegati e clienti, che possono fornire un feedback in merito al servizio ricevuto. Il sistema è stato sviluppato per dispositivi Android. L'architettura utilizzata per sviluppare l'applicazione è di tipo client-server. I dati necessari al funzionamento dell'applicazione sono conservati in un database online

Ultrasensitive N-photon interferometric autocorrelator

We demonstrate a novel method to measure the Nth-order (N=1, 2, 3, 4) interferometric autocorrelation with high sensitivity and temporal resolution. It is based on the combination of linear absorption and nonlinear detection in a superconducting nanodetector, providing much higher efficiency than methods based on all-optical nonlinearities. Its temporal resolution is only limited by the quasi-particle energy relaxation time, which is directly measured to be in the 20 ps range for the NbN films used in this work. We present a general model of interferometric autocorrelation with these nonlinear detectors and discuss the comparison with other approaches and possible improvements

Innovation in accounting historiography: Where to from here?

The world is facing difficult, uncertain and challenging times, which have consequences for accounting practice, education and research. This new and uncertain environment may lead us to conclude that accounting research should focus on the present and develop answers to be implemented in the future. Does this mean that accounting history must be put aside for the moment? We start from the position that accounting history continues to matter and that accounting history researchers have developed their perspectives and methodological and theoretical approaches considerably since the early 1990s in terms of diverse fields and topics of research. This article aims to explore how accounting history research can expand by seeking innovation in theories, sources, methodologies and writing. It demonstrates that accounting history is not static and researchers can contribute to its further recognition and dissemination. Through the innovative study of the past, researchers may continue to contribute to new and informed ways for the world to be managed and governed

Governance and control of sharing economy platforms: hosting on Airbnb

Sharing economy platforms have recently surged as popular venues of business enabling people around the world to digitally interact and temporarily exchange their under-utilised assets. Beyond a very small number of exploratory studies of accounting practices underpinning these digital platform organisations, little is known about their governance and management control. This paper examines the governance and management control exercised by a digital platform owner over global users exhibited by Airbnb, a successful and pervasive sharing economy platform in the holiday accommodation sector. Through netnographic method, this study investigates the platform owner governance and control issues with respect to hosts. The analysis reveals the platform owner using predominantly formal bureaucratic control systems as mechanisms to govern and control its users. Through users’ compliance, they and their activities are made visible to the platform owner, which in turn maintains control over the value creation process. This study provides insights into how accounting systems are mobilised in digital platforms to facilitate their governance through mechanisms of surveillance, monitoring control over digital users worldwide, and how innovative and disruptive phenomena nonetheless rely on traditional technologies of governance to maintain power and control

Morphometric and phytochemical characterization and elevation effect on yield of three potato landraces of the Ligurian Apennines (Northern Italy)

The great adaptability, productivity and importance in human diet conditioned the diffusion of potato (Solanum tuberosum L.) in very different areas, leading to the formation of numerous landraces through anthropic or natural selection. Genoa mountainous inland is an historical area for potato cultivation and landraces are preserved by farmers associations as “Consorzio della Quarantina”. The aim of this study was the phytochemical and morphometric characterization of three potato landraces of the consortium (Quarantina Bianca, Quarantina Prugnona and Rubra spes) analysing the bio-agronomical performance at different elevations. The commercial cultivar Kennebec was used as control. For the morphometric analysis, the results of pairwise MANOVA shows that only Quarantina Bianca does not present significant differences with Kennebec in the mean shape. The four potato varieties resulted significantly different for the most of the considered phytochemical aspects (among content in ash, starch, solanine, total flavonoids, total phenols, chlorogenic acid, caffeic acid, ferulic acid and radical scavenging activity only starch and solanine content didn’t result statistically different). A remarkable result was a more consistent yield for all the varieties with the increase of elevation in the agronomical trials. We can conclude that Genovese landraces are a good choice to exploit Genovese mountain marginal territories

Superconducting series nanowire detector counting up to twelve photons

We demonstrate a superconducting photon-number-resolving detector capable of resolving up to twelve photons at telecommunication wavelengths. It is based on a series array of twelve superconducting NbN nanowire elements, each connected in parallel with an integrated resistor. The photon-induced voltage signals from the twelve elements are summed up into a single readout pulse with a height proportional to the detected photon number. Thirteen distinct output levels corresponding to the detection of n=0-12 photons are observed experimentally. A detailed analysis of the excess noise shows the potential of scaling to an even larger dynamic range.Comment: 13 page