Atomic relaxation processes near conducting and superconducting surfaces

The aim of this thesis is to investigate the interaction of neutral atoms with conducting and superconducting surfaces. Experimental advances in the magnetic confinement of ultracold atoms have shown that they can act as a powerful tool in a wide range of phenomena such as electric and magnetic field imaging and matter wave interferometry. Coherent manipulation of atoms and ever smaller magnetic traps are essential elements in the implementation of integrated quantum devices for fundamental research, quantum information processing and precision measurements. This thesis considers main influences on atoms placed within three different environments which are useful in achieving miniaturization and efficient control in atomic magnetic traps: carbon nanotubes, dielectric surfaces and superconducting thin films. The possibility of holding atoms near the outside of a carbon nanotubes will be addressed. In order to give a qualitative analysis of the atom-nanotube interaction, thermally induced spin-flips and the Casimir-Polder potential have been considered. The comparison between these two effects is presented in this thesis. It indicates that the Casimir-Polder force is the dominant loss mechanism and an estimation of the minimum trapping distance is given based on its effect. Secondly, a first-principles derivation of spatial atomic-sublevel decoherence near dielectric and metallic surfaces will be presented. The rate obtained for the decay of spatial coherence has dual implications, on one hand, it can be considered as a measure of the coherence length of the fluctuations of the electromagnetic field arising from a given substrate. On the other hand, it turns out to be relevant for quantum information encoding in double well potentials. Finally, the known spin-flip transition rate will be linked to the flux noise spectrum in superconducting thin films showing the feasibility of using cold atomic clouds in the investigation of vortex dynamics.Imperial Users onl

Tra vita contemplativa e vita attiva: il De Officiis di Cicerone e le sue radici aristoteliche

This paper examines the relationship between contemplative and active life in Cicero’s last philosophical work, the De officiis. This highly studied topic in the philosopher’s work and life embraces fundamental issues such as sapientia and prudentia, utilitas, and the characteristics of human nature, in its twofold and irreducible value, both descriptive and prescriptive.The second part of the paper explores how Cicero thought about these themes in connection with Aristotelian philosophy and, more specifically, with the ethical-political reflection of the Stagirite. In fact, Cicero’s text contains evident references, albeit with interesting repositioning and changes, to crucial questions about contemplative and active life already posed by Aristotle, above all the role and meaning of sapientia and prudentia, notions that Cicero explicitly connects, although in a thorny process of concordia discors, with the ones of σοφία and φρόνησι

Os \u201cmuitos\u201d se dizem de muitos modos. Reflex\uf5es plat\uf4nicas e aristot\ue9licas sobre a natureza, as escolhas e o destino dos polloi

Este artigo pretende confrontar as reflexões de Platão e Aristóteles sobre o tema da natureza dos “muitos”, ou seja, seus comportamentos, os modos de ser e as escolhas de vida da maioria dos seres humanos. Mais em geral, pretende mover-se no interior de um “paradigma interpretativo” centrado na figura teórica do pollachos legomenon, isto é, sobre o reconhecimento de que “qualquer coisa é e é dizível de muitos modos” e que, portanto, os esquemas de leitura e de descrição do real devem ser multiplicados e mantidos abertos ao máximo.The purpose of this paper is to offer a confrontation between Plato’s and Aristotle’s reflections on the nature of the “many”, i.e., the behaviour, the ways of being, and the life choices of the majority of the human beings. Furthermore, we also intend to base our analysis in accordance with an “interpretative paradygm” having as its core the pollachos legomenon, i.e., the recognition that “anything is and can be said monifold”, what brings us to the conclusion that reading procedures and the descriptions of reality must be multiplied and kept as open as possible

Design of magnetic traps for neutral atoms with vortices in type-II superconducting micro-structures

We design magnetic traps for atoms based on the average magnetic field of vortices induced in a type-II superconducting thin film. This magnetic field is the critical ingredient of the demonstrated vortex-based atom traps, which operate without transport current. We use Bean's critical-state method to model the vortex field through mesoscopic supercurrents induced in the thin strip. The resulting inhomogeneous magnetic fields are studied in detail and compared to those generated by multiple normally-conducting wires with transport currents. Various vortex patterns can be obtained by programming different loading-field and transport current sequences. These variable magnetic fields are employed to make versatile trapping potentials.Comment: 11 pages, 14 figure

Programmable trap geometries with superconducting atom chips

We employ the hysteretic behavior of a superconducting thin film in the remanent state to generate different traps and flexible magnetic potentials for ultra-cold atoms. The trap geometry can be programmed by externally applied fields. This new approach for atom-optics is demonstrated by three different trap types realized on a single micro-structure: a Z-type trap, a double trap and a bias field free trap. Our studies show that superconductors in the remanent state provide a new versatile platform for atom-optics and applications in ultra-cold quantum gases

Volunteer engagement as a form of political participation: A study on Italian emerging adults

Despite that the political and civic engagement are fundamental, recent trends suggest that in several democratic countries around the world youths' disengaged from politics are increasing, but it seems that they are more involved in volunteer activities beneficial for the community in which they are involved. This study examined differences between youths who consider their volunteer engagement as a form of political participation and who do not interpret their involvement in this way. The sample consisted of 247 Italian emerging adults, aged between 18 and 30 years, who were actively involved in volunteer groups: environmental associations; cultural associations; social associations; inclusive/solidarity economy associations. In our results, the youth who considered their volunteer activity as a form of political participation were slightly older, more left-wing oriented, and were more involved in some contexts of volunteerism than their counterparts who do not view their volunteer involvement as a form of political participation

On the feasibility of studying vortex noise in 2D superconductors with cold atoms

We investigate the feasibility of using ultracold neutral atoms trapped near a thin superconductor to study vortex noise close to the Kosterlitz-Thouless-Berezinskii transition temperature. Alkali atoms such as rubidium probe the magnetic field produced by the vortices. We show that the relaxation time $T_1$ of the Zeeman sublevel populations can be conveniently adjusted to provide long observation times. We also show that the transverse relaxation times $T_2$ for Zeeman coherences are ideal for studying the vortex noise. We briefly consider the motion of atom clouds held close to the surface as a method for monitoring the vortex motion.Comment: 4 pages, 1 figur

Attaccamento ai genitori e disagio emotivo in adolescenti appartenenti a famiglie italiane, miste e migranti: Un approccio multi-metodo

Una ricerca compiuta in italia con metodologia quantitativa e qualitativa per approfondire l'attaccamento ai genitori e il disagio emotivo in adolescenti appartenenti a famiglie italiane, miste e migranti.I partecipanti erano 509 adolescenti (55% maschi) che frequentavano varie scuole medie e superiori del centro-est Italia. La loro et\ue0 variava tra gli 11 e i 19 anni (M = 13.6, DS = 2.2). Il campione era composto da tre gruppi: 261 adolescenti provenivano da famiglie italiane; 100 da famiglie miste (in cui un solo genitore aveva la nazionalit\ue0 italiana); e 148 da famiglie migranti. I risultati hanno mostrato che gli adolescenti provenienti da famiglie migranti si differenziano dai loro coetanei provenienti da famiglie italiane o miste in quanto manifestano con minore frequenza un forte attaccamento a entrambi i genitori e con maggiore frequenza un debole attaccamento a entrambi. Inoltre, gli studenti di famiglie migranti riportano pi\uf9 sintomi ansiosi e depressivi dei coloro coetanei appartenenti alle famiglie italiane e miste. In generale, gli adolescenti con un forte attaccamento a entrambi i genitori manifestano i livelli pi\uf9 bassi di sintomi depressivi e ansiosi mentre un legame ambivalente o evitante sono associati a maggiori disagi emotivi. I risultati sono interpretabili in linea con la letteratura che vuole i compiti di sviluppo relazionali pi\uf9 complessi in adolescenti di famiglie migranti mentre nelle famiglie miste la coppia sarebbe gi\ue0 abituata a negoziare tra culture differenti rendendo meno complessa la costruzione dell\u2019identit\ue0 nei figli