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Il Tempo della Scienza

Seminari tecnici 2014

Sala Conferenze (Edificio M)
Strada delle Cacce 91, Torino

Data Titolo Relatore
20 gennaio
ore 10
Partecipazione INRIM al confronto 'Supplementary Comparison EURAMET.EM-S32'
"Comparison of resistance standards at 1 TΩ and 100 TΩ":
sistemi di misura INRIM, analisi dei dati e interazioni con il Laboratorio pilota

lucidi

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Nel 2009 l'INRIM ha partecipato al confronto di misura EURAMET.EM-S32 di elevatissime resistenze a livello 1 TΩ e 100 TΩ a cui hanno partecipato 18 Istituti Metrologici Europei. Vengono descritti i sistemi ed incertezze di misura INRIM, l'analisi dei risultati per il trattamento di dati provenienti da più campioni di pari valor nominale. Viene sintetizzata l'interazione tra l'INRIM ed il METAS per la definizione dell'esito definitivo del confronto.
Flavio Galliana e Pier Paolo Capra
INRIM
22 gennaio
ore 11
Cold atoms experiments at University of São Paulo:
from quantum turbulence to compact atomic clocks
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We shall discuss the experiments and results using cold atoms to prepare BEC, to investigate quantum turbulence and to produce atomic clocks. In special, the compact clock, using an expanding cloud of cold atoms will be discussed.
Vanderlei Salvador Bagnato
Instituto de Física de São Carlos
Universidade de São Paulo
3 febbraio
ore 14
Photonic States Manipulation in Atomic Ensembles
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Quantum information processing requires efficient encoding, manipulation and storage of quantum states. Photons are excellent carriers of quantum information, since they travel fast without being affected by external disturbances. On the other hand, cold atomic ensembles are a very versatile tool to store, manipulate and retrieve quantum states of light. In the past decade, they have been extensively used to store and retrieve photonic states by using either the so called Electromagnetically Induced Transparency (EIT) protocol, or the DLCZ protocol, where the detection of a Raman photon triggers the creation of a collective atomic excitation in a lambda-medium. The shared excitation can be reconverted later into a single photon leaving the ensemble. The process has been extensively investigated in the photon counting regime showing the non-classical character of the emerging photonic state. Only very recently the photonic states leaving the atomic ensemble have been characterized by quantum homodyne tomography. The state is hence completely described in the continuous variables picture by the reconstructed Wigner function giving complete information on a welldefined spatial-temporal mode.
Atomic ensembles can be also used for manipulating photonic states by atomic interactions and they are promising candidates to reach strong-nonlinearities at the single-photon level. Photonic states can be converted into strongly interacting particles, like collective excitations involving Rydberg atoms. Interactions between Rydbergs in fact lead to a "blockade" phenomenon, where each Rydberg atom blocks the excitation of its neighbors, which can result in strong nonlinearities.
Valentina Parigi
Laboratoire Kastler Brossel
Université Pierre et Marie Curie, Ecole Normale Supérieure, CNRS, Paris
12 febbraio
ore 9:30
ed.D p.1
Including disorder in micromagnetic simulations: the road to imperfection
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In this seminar you will see how material imperfections can be included in micromagnetic simulations. Understanding domain wall motion in magnetic nanowires is of paramount importance for the development of future spintronics devices and simulations are a powerful tool to investigate this motion. However, more often than not the effects of material imperfections are not taken into account in these simulations.
A method will be shown to characterize simulated defects and its application to find 2 possible implementations that give rise to defects with properties that correspond to experimental values. The effects of this disorder on current driven vortex domain wall motion will illustrate why disorder should be taken into account. Furthermore, as there is a suspected link between the experimentally measured disorder and the grains in material samples. A computationally efficient way of simulating polycrystalline materials using voronoi cells will also be presented.
Jonathan Leliaert
University of Ghent
12 febbraio
ore 14:30
Astroparticle physics in space
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Roberto Battiston
Università di Trento
Dipartimento di Fisica
19 febbraio
ore 11
Optical Lattice Clocks and Applications
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Research on optical frequency standards based on cold atoms or ions has shown a great advance in the last few years. Among others, alkaline-earth atoms trapped in an optical lattice have demonstrated unprecedented stability. Recently a strontium lattice clock demonstrated an uncertainty of 6e-18, the best in frequency standards up to date. The stability and accuracy of optical frequency standards will benefit many applications and innovations, such as realization and dissemination of units in the Système International (SI), quantum simulations, relativistic geodesy, test of fundamental constants variation and tests of fundamental physics.
In the talk I will describe the development of an optical lattice clock based on ytterbium atoms and the perspective for the near future. Comparison with other clocks is planned, both local and remote, that will allow a proof-of-principle relativistic geodesy experiment. In addition, remote comparison with a quantum degenerate ytterbium gas experiment developed in Florence will be useful for studies of collisional physics and quantum simulations.
Marco Pizzocaro
INRIM
26 febbraio
ore 15:30
Un'infrastruttura in fibra ottica per la disseminazione di frequenza a 5e-19 su scala nazionale ed europea

A fiber optical link for frequency dissemination at 5e-19 on a European scale
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Currently, time and frequency dissemination is performed with satellite microwave links. These techniques strongly limit the comparison of remote primary frequency standards, and are completely inadequate for the comparison of optical clocks. In recent years, an alternative method based on optical fiber has been developed, which improves the resolution by 5 orders of magnitude. This is not only beneficial in time and frequency metrology, but paves the way for new opportunities in fundamental physics, geodesy and radioastronomy as well.
INRIM has developed a 642 km optical link with the European Laboratory for Non Linear Spectroscopy (LENS) in Firenze. This backbone has enabled absolute spectroscopic measurements between the two laboratories and will be upgraded to connect other research centres in Italy ( Medicina (Bologna) Radio-telescopes, National Institute of Optics in Firenze, National Council of Research in Milano) and in Europe. I will describe the optical link, the fiber-based remote comparison of atomic clocks, and the future applications.
Cecilia Clivati
INRIM
27 marzo
ore 9
ed.A p.2
Comparison of non-classicality and Decoherence between photon added and photon subtracted squeezed coherent state
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Non-classicality in a state of light is a valuable resource for quantum information processing. Non-classicality is manifested by certain criteria such as sub-Poissonian distribution of photon numbers, oscillation in the photon number distribution and negativity of the Wigner function. Employing the technique of Integration within an Ordered Product (IWOP), I have calculated and compared the non-classicality of photon added and photon subtracted squeezed coherent states. I have found that photon addition generates more non-classicality in a squeezed coherent state than photon subtraction. Decoherence of such states in amplitude and phase damping channel has also been analysed in this work. How the photon number distribution will change under the influence of Decoherence will also be discussed.
Nigam Samantaray
INRIM
11 aprile
ore 11
ed.D p.1
Dai vulcani siciliani ai villaggi neolitici piemontesi. Il viaggio dell'ossidiana attraverso lo studio delle sue proprietà magnetiche
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In questo lavoro, si à posta attenzione ad alcuni parametri sperimentali per distinguere le diverse distribuzioni e dimensioni dei granuli magnetici (ossidi di ferro: magnetite, titano-magnetite) nei principali giacimenti di ossidiana del Mediterraneo. La potenzialità del metodo per tracciare la provenienza di manufatti in ossidiana di interesse archeologico è stata valutata confrontando campioni geologici di cinque isole (Lipari, Monte Arci – Sardegna, Palmarola, Pantelleria, Melos) con i campioni costitutivi di una collezione di lamelle provenienti dal sito neolitico di Castello d'Annone, in provincia di Asti (22 campioni). Sono state misurate: la suscettività magnetica iniziale x, la suscettività anisteretica xa e la magnetizzazione rimanente (IRM) a T = 293 K (IRM293) e 77 K (IRM77). Sono state inoltre analizzate le forme dei cicli di isteresi, sia a T = 293 K sia a T = 77 K. Lo studio dei parametri magnetici ricavabili da queste misure permette una stima della distribuzione dei granuli ferrosi presenti nell'ossidiana, distinguendone il contenuto in superparamagnetici (SP), singolo dominio (SD), pseudo singolo dominio (PSD) e multidominio (MD). L'indicazione di provenienza ricavata dalle misure conferma le ipotesi già avanzate dagli studi archeologici nell'Italia nord-occidentale sull'esistenza nel Neolitico di una via di commercio con Lipari e la Sicilia, oltre a quella con la Sardegna, consolidata e favorita dalla vicinanza.
Elena Pavesio
Università di Torino
14 aprile
ore 12
Control of Quantum Sensors
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The success of quantum-enhanced sensors relies on precise control of the experimental systems to protect them from undesired sources of noise. Unfortunately, simple application of known strategies to reduce decoherence does not necessarily translate into an improvement of phase measurements: techniques such as dynamical decoupling that eliminate decoherence also eliminate the very signal that one wishes to measure.
In this talk I will show how to extend control techniques to quantum metrology tasks, achieving a better and more flexible compromise between sensitivity and noise protection. In addition, tailoring the sensor dynamic can help reveal temporal and spatial information about the target. We can for example use coherent control of quantum sensors to simultaneously reconstruct the arbitrary profile of time­varying fields and correct for unwanted noise sources; or we can achieve high frequency resolution, thus allowing precise spectroscopy.
I will illustrate applications of these strategies in experimental implementations based on the Nitrogen­Vacancy center in diamond.
Paola Cappellaro
Nuclear Science and Engineering Department
Massachusetts Institute of Technology
15 aprile
ore 11
Atomic Frequency Standards in Brazil - Research and ongoing applications
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In the recent years, using atomic transitions have become more and more frequent in the definition of reference standards. The measurement capability reached by microwave and optical frequency standards plays a fundamental role on these definitions. Our research group has been establishing experiments in some of the several kinds of atomic standards, and the goal of this presentation is to present the state of the art in our laboratories. The results concern the 133Cs atomic fountain, the 133Cs compact clock, the experiment with 88Sr, the structure under development for time and frequency scientific metrology and applications in course for the use of such accurate and stable references.
Daniel Varela Magalhaes
São Carlos School of Engineering
University of São Paulo, Brazil
11 giugno
ore 10:30
Superconducting nanowires for single-photon detection
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Superconducting nanowire single photon detectors (SNSPDs) is an emergent technology which is rapidly achieving unprecedented performances: single photon sensitivity in the 0.5–3.0 micron range with detection efficiency above 90%, dark count rate below 1 kHz, dead time of a few nanoseconds, and timing jitter as low as 20 ps. Photon number resolving is also possible and very recently counting capability up to 12 photons has been demonstrated. These characteristics are attractive for quantum technologies and high sensitivity long-distance communications, as well as for atmospheric remote sensing and biological/medical sensing of ultra weak photon sources. As is often the case in applied nanotechnology, it is a challenge to make devices that match with the macroscopic dimensions of the available light sources (laser spots, etc). Both the fast temporal response and the device sensitivity is generally degraded when the SNSPD active area is increased.
Here, a general overview of SNSPD will be given and our recent results will be presented on novel SNSPD configurations for scaling up to macroscopic dimensions without losing the performance of the active elements, thus enabling practical use of this nanotechnology. Presently NbN is the material of choice for SNSPD. Results on alternative materials (WSi, YBCO) will be also presented.
Roberto Cristiano
Istituto Superconduttori, Materiali innovativi e dispositivi (SPIN) del CNR, Pozzuoli (Napoli)
11 giugno
ore 15
Acustica subacquea: stato delle conoscenze e prospettive applicative
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L'esplorazione dell'ambiente marino, in primo luogo di quello profondo, rappresenta una delle ultime grandi sfide. L'ostilità di questo ambiente all'uomo e l'impossibilità di ricorrere alle onde elettromagnetiche impongono l'uso della propagazione acustica. Nei suoi cento anni di storia l'acustica subacquea si è sviluppata a partire dall'esigenza di essere di ausilio alla navigazione oceanica, ricevendo un enorme impulso nel periodo bellico e post-bellico con la lotta antisommergibili, fino ad interessare al giorno d'oggi quasi ogni ambito applicativo delle scienze e tecnologie marine.
Il seminario presenta alcuni casi di studio tra i più significativi con una descrizione dello stato dell'arte e delle attuali prospettive di sviluppo, con particolare attenzione al tema della metrologia.
Silvano Buogo
Istituto di Acustica e Sensoristica "O. M. Corbino" del CNR
15 luglio
ore 15:30
ed.D p.1
Opto-Electronic Properties of Bismuth Oxide Thin Films and Applications
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Bismuth oxide Bi2O3 has interesting technological applications, which have not been largely explored due to the particular polymorphism of the material. Among the interesting properties, it is worth mentioning a large energy gap (from 2 to 3.96 eV depending on the phase), high refractive index, dielectric permittivity, noticeable photoconductivity and photoluminescence. Moreover, one of its phases presents the highest ionic conductivity. Bismuth Oxide has five polymorphic forms: α, β, γ, δ and ω-Bi2O3. Among them, the low-temperature α and the high-temperature γ phases are stable and the others are metastable. The face-centered cubic δ-Bi2O3 is stable over a narrow range 729–825oC (melting point) and it is the high ionic conductivity phase. Remarkably, it has been proved that the deposition of nanocrystalline thin films allows the stabilization of the high temperature phase (δ) at room temperature. In order to study deeply the properties and therefore possible applications of Bismuth oxide thin films for the energy and environmental areas, Bismuth oxide thin films were deposited by reactive magnetron sputtering from a Bi2O3 target (99.95 at%) using radio frequency and an Ar/O2 atmosphere (80/20). The films were deposited on silicon and glass substrates as a function of the power (PW: 100-200 W) and the substrate temperature (Ts: 125-250oC). The films were characterized in terms of the structural identification by X-ray diffraction (XRD) and Raman spectroscopy, the elemental composition by X-ray photoelectron spectroscopy, the optical properties were determined by spectroscopy ellipsometry and the electrical resistivity by analyzing the current-voltage curves measured using two-concentrically circular Pt electrodes deposited on the surface.
The results indicated that stoichiometric Bi2O3 films were obtained but according to the Ts and PW, the crystalline structure changed from the delta-phase, at the lowest energetic conditions, to beta and alpha as the substrate temperature or power increased. Micro Raman showed that under energetic conditions, the films were not spatially uniform; presenting phase differences (α and β). The electrical measurements of the as-deposited films (on glass) showed the response of a highly electrical resistance material.
In this presentation, the evaluations of the Bismuth oxide thin films for two possible energetic and environmental applications are presented. Firstly, we explore the photocatalytic response of the films studying the degradation of color dyes (methyl orange) under different conditions of illumination, agitation and pH. The preliminary results indicated a response comparable to the well-known TiO2 photocatalytic material. Secondly, the δ-phase films were stabilized up to 500oC by the addition of Ta ions opening the possibility of using them as the electrolyte layer for micro solid oxide fuel cells.

Acknowledgements: This research received funding from the European Community Seven Framework Programme (FP7-NMP-2010-EU-MEXICO) and CONACYT under grant agreements n. 263878 and 125141, respectively.
Sandra E. Rodil
Universidad Nacional Autónoma de México
21 luglio
ore 17
Nanoscienza e nanotecnologia al NEST
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Nanotechnology is moving fast towards becoming a trillion dollar market, as predicted by the National Science Foundation back in 2000 for year 2015. This large figure is the result of the pervasive impact of nanotechnology in many different fields notably nanomaterials, but above all in the pharmaceutical and biomedical sectors.
In this talk I shall present some of the recent activities at NEST, the National Enterprise for nanoScience and nanoTechnology both in the context of nanostructured materials and devices for ICT and in the biomedical sectors. I shall also discuss the role of standardization and certification of nanoprocesses to ensure the exploitation to the full potential of these novel methodologies.
Fabio Beltram
Scuola Normale Superiore, Laboratorio NEST
22 luglio
ore 11
A classic never gets old
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The Einstein relation between stimulated emission, many aspects of which can be understood classically, and spontaneous emission, which it is generally agreed cannot be understood classically, can be seen as the origin of quantum optics. In this talk we show that similar relations can be found in nonlinear optics, starting with the generation of photon pairs by parametric fluorescence. This offers a new perspective on the physics unifying classical and quantum integrated optics.
Marco Liscidini
Università degli Studi di Pavia
28 luglio
ore 11
Cross-Spectrum Measurement of PM Noise in the Presence of AM Noise
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We measure the PM noise of an oscillator by comparing it with two independent references (synthesisers), and by using two separate phase meters (mixers). The cross spectrum method enables the rejection of the background noise, and provides enhanced sensitivity. However, AM noise can result in serious under-estimation of the DUT noise, which is of course embarrassing.
Let us denote with c(t) the physical quantity to be measured (oscillator PM noise), with a(t) and b(t) the background of the two instruments, and with x(t) = c(t)+a(t) and y(t) = c(t)+b(t) the signals available at the instrument outputs. Assuming that the process are stationary and ergodic (the physical experiment is repeatable and reproducible) and that the two instruments are independent, the average correlation of x and y gives the statistical properties of c(t). The single-channel noise is rejected proportionally to the square root of the number m of averages, and ultimately to the square root of the measurement time.
A major problem has been discovered recently, that the oscillator AM noise results in cor- related noise at the two outputs x(t) and y(t), and ultimately in a systematic error in the measurement of the oscillator PM noise. The eect of AM noise can be either correlated or anti-correlated. In the latter case, the DUT noise is under-estimated.
We will review the cross spectrum method, and discuss the eect of AM noise.
Enrico Rubiola
FEMTO-ST Institute, Dept. Time and Frequency
CNRS / École Nationale Supérieure de Mécanique et des Microtechniques (ENSMM) / Université de Franche-Comté (UFC), Besançon, France



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