3,253 research outputs found
Quantum dynamics of periodically driven superconducting nanocircuits
No full textFrom the introduction: [...] In this thesis we investigate the effect of a periodic external driving on the transport properties of superconducting nanocircuits. We mainly focus on the properties of the Cooper pair shuttle. We will however consider also quantum dynamics of several superconducting grains connected in series by means of Josephson junctions, i.e. a Josephson junction chain. We will pay a particular attention to the role of a chain in transferring quantum information. The thesis is organized as follows. In Chapter 1 we introduce the relevant physics of superconducting nanocircuits. The main effect we discuss is the coherent transfer of Cooper pairs due to the Josephson effect. We consider the Josephson effect in bulk superconductors and then in mesoscopic systems where charging effects become important. In the rest of the thesis we discuss the effect of the external periodic driving on superconducting nanocircuit. It is divided into two parts. The first part is dedicated to the transport properties of the Cooper pair shuttle. We explore both charge (Chapters 2 and 3) and Josephson (Chapter 4) dominated regimes. In the first regime we are mostly interested in the effect of decoherence on the Josephson current. They are presented in Chapter 2 where we also propose a possible nonmechanical realization of the Cooper pair shuttle’s physics. Charge transfer in the Cooper pair shuttle is achieved as a result of an out of equilibrium process due to the mechanical motion usually associated with dissipation. The role of coherent Cooper pair transfer in presence of dissipation is the key issue in Chapter 3 where we calculate the current noise. We determine the whole current distribution function by means of the formalism of the Full Counting Statistic which is reviewed in Appendix A. The opposite limit, where the Josephson energy dominates over the charging energy, is investigated in Chapter 4. In this case the Cooper pair shuttle behaves like a quantum kicked rotator, which is a chaotic system in the classical limit. We discuss how the Cooper pair shuttle can be used to observe characteristic features of classically chaotic quantum system and we investigate the effect of the chaotic dynamics on the transport properties of the shuttle. In the second part we analyze a Josephson junctions chain as a channel for quantum information transfer. We investigate the transfer of a quantum state between the two ends of the chain and we discuss a protocol to measure the transferred state. We include in the Appendices C, D, E all the technical discussions and calculations. Appendices A and B have a different role: They are extensive introductions to the subject of full counting statistics and quantum dynamics of classically chaotic system respectively. They are not the main topic of this PhD thesis, but turn out to be of some importance for what is discussed in Chapters 3 and 4
Transport properties of a periodically driven superconducting single-electron transistor
No full textWe discuss coherent transport of Cooper pairs through a Cooper pair shuttle. We analyze both the dc and ac Josephson effects in the two limiting cases where the charging energy EC is either much larger or much smaller than the Josephson coupling EJ. In the limit EJ EC we present the detailed behavior of the critical current as a function of the damping rates and the dynamical phases. The ac effect in this regime is very sensitive to all dynamical scales present in the problem. The effect of fluctuations of the external periodic driving is discussed as well. In the opposite regime the system can be mapped onto the quantum kicked rotator, a classically chaotic system. We investigate the transport properties also in this regime, showing that the underlying classical chaotic dynamics emerges as an incoherent transfer of Cooper pairs through the shuttle. For an appropriate choice of the parameters the Cooper pair shuttle can exhibit the phenomenon of dynamical localization. We discuss in detail the properties of the localized regime as a function of the phase difference between the superconducting electrodes and the decoherence due to gate voltage fluctuations. Finally we point out how dynamical localization is reflected in the noise properties of the shuttle
A imagem de Alessandro Baricco no Brasil
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Estudos da Tradução, Florianópolis, 2013.Com a intenção de delinear o modo pelo qual o escritor italiano Alessandro Baricco se inseriu no sistema literário brasileiro e os caminhos percorridos pelos seus livros traduzidos, esta dissertação dá voz às experiências tradutórias de seus tradutores. A inserção de Bariccono Brasil tem seu início em 1997, através de uma proposição da Profa. Dra. Roberta Barni à editora Iluminuras da tradução de Oceano Mare. A partir daí, outras sete obras foram publicadas no Brasil, sendo três delas traduzidas por Roberta Barni e as outras quatro por quatro tradutores diferentes. De um lado, considera-se o tradutor como figura principal namediação entre culturas, e, de outro, se analisa a realidade desta figuradentro do sistema literário, sua invisibilidade, seus limites e o exercíciode sua profissão. A pesquisa conta, ainda, com críticas e resenhas referentes ao autor italiano publicadas em jornais consagrados no Brasil, considerando estas como parte constituinte da imagem de Baricco refletida em território nacional. Abstract : Intending to delineate the way the Italian writer Alessandro Baricco has been inserted in the Brazilian literary system and the paths his translated books have followed, this thesis gives voice to the translating experiences of his translators. Baricco's insertion in Brazil began in 1997, through a personal project of Dr. Roberta Barni, with her translation of Oceano Mare. Since then, seven other of his works have been published in Brazil, three of which were translated by Roberta Barni and the other four by four different translators. On the one hand,the translator is considered as the main figure in mediation betweencultures and, on the other, this figure's reality is analyzed within theliterary system: its invisibility, its limits and its professional practice. Criticisms and reviews of this Italian author published in well established Brazilian newspapers are also considered, with the understanding that they are part of Baricco's image reflected here
La maturità di Alessandro Fei del Barbiere, in bilico tra Maniera e Riforma
No full textThis article studies the mature career of the Florentine painter Alessandro Fei del Barbiere (1537-1592), beginning with the rediscovery of the 'Ascension' altarpiece formerly in the Albizi Chapel in the destroyed church of San Pier Maggiore, Florence. Studying this painting and others recorded in 1584 by the biographer Raffaello Borghini, such as the two altarpieces for Santa Maria delle Grazie and the Madonna dell'Umiltà in Pistoia, the author reconstructs a body of works showing how in the 1580s Fei gradually went beyond the archaic style of his apprenticeship - he had been trained by Ridolfo del Ghirlandaio and Pierfrancesco Foschi, but was also marked by the Maniera of Vasari - evolving towards naturalism in both mimesis and pictorial handling. In Florence, his development partly parallels that of Santi di Tito and his circle, but Fei was also influenced by a probable sojourn during the early part of that decade in Rome, where he could have been inspired by Girolamo Muziano and the painters working for Pope Gregory XIII. Among other proposals, the author suggests that the artist was responsible for decorating the chancel of Fiesole Cathedral (c. 1584-1589), which consisted of an altarpiece, only rarely discussed by scholars, and a cycle of frescoes hitherto attributed to Nicodemo Ferrucci
Quantum Effects on the Synchronization Dynamics of the Kuramoto Model
No full textThe Kuramoto model serves as a paradigm for describing spontaneous
synchronization in a system of classical interacting rotors. In this study, we
extend this model to the quantum domain by coupling quantum interacting rotors
to external baths following the Caldeira-Leggett approach. Studying the
mean-field model in the overdamped limit using Feynman-Vernon theory, we show
how quantum mechanics modifies the phase diagram. Specifically, we demonstrate
that quantum fluctuations hinder the emergence of synchronization, albeit not
entirely suppressing it. We examine the phase transition into the synchronized
phase at various temperatures, revealing that classical results are recovered
at high temperatures while a quantum phase transition occurs at zero
temperature. Additionally, we derive an analytical expression for the critical
coupling, highlighting its dependence on the model parameters, and examine the
differences between classical and quantum behavior.Comment: 14 pages, 5 figure
Tra socialdemocrazie e Perestrojka. Le relazioni internazionali del Pci attraverso le carte di Alessandro Natta
No full textThis essay reconstructs the foreign policy of the Italian Communist Party during the four
years of Alessandro Natta’s secretariat (1984-1988) through largely original archival documentation,
from the Alessandro Natta Fonds of the Historical Archive of the Chamber of
Deputies. Natta’s papers are also cross-referenced with those kept in the PCI Archive at the
Gramsci Foundation. The author analyses the relationship that the PCI establishes with
Gorbachev’s Perestroika, Deng’s China, and European social democracies during the last
years of the Cold War
Implementation of quantum communication protocols in Josephson junction arrays
No full textWe discuss simple protocols to realize state transfer with high fidelity in Josephson junction arrays. We consider both the cases of constant and properly modulated couplings between the site of the chain. We investigate the influence of static disorder both in the Josephson energies and in the coupling to the background gate charges and we show that they can lead to a fractal fidelity. We also analyze the readout process, and its backaction on the state transfer. © World Scientific Publishing Company
Decoherence in a Cooper pair shuttle
No full textWe examine decoherence effects in the Josephson current of a Cooper pair shuttle. Dephasing due to gate voltage fluctuations can either suppress or enhance the critical current and also change its sign. The current noise spectrum displays a peak at the Josephson coupling energy and shows a phase dependence
Volta Alessandro
No full textThe New Dictionary of Scientific Biography (extension and updating of the Dictionary of Scientific Biography) is one of the most substantial reference works in the field of the history of science. An up-to-date overview on Alessandro Volta's science with new perspectives offered by the author. Information and critical analysis is also provided on the main secondary literature produced on this main protagonist of enlightenment science after the 1976 entry "Volta Alessandro" in the Dictionary of Scientific Biography
Solid-state quantum communication with Josephson arrays
No full textJosephson junction arrays can be used as quantum channels to transfer quantum information between distant sites. In this paper we discuss simple protocols to realize state transfer with high fidelity. The channels do not require complicated gating but use the natural dynamics of a properly designed array. We investigate the influence of static disorder both in the Josephson energies and in the coupling to the background gate charges, as well as the effect of dynamical noise. We also analyze the readout process, and its back action on the state transfer
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