12,702 research outputs found
Computational and experimental analysis of surface acoustic wave propagation on piezoelectric GaAs layer
No full textMABS validation through repeated execution and data mining analysis
No full textAgent Based Modelling is the most interesting and advanced approach for simulating a complex system: in a social context, the single parts and the whole are often very hard to describe in detail. Besides, there are agent based formalisms which allow to study the emergency of social behaviour with the creation and study of models, known as artificial societies. Thanks to the ever increasing computational power, it's been possible to use such models to create software, based on intelligent agents, which aggregate behaviour is complex and difficult to predict, and can be used in open and distributed systems. Data mining is born in the last decades in order to help users in finding useful knowledge from the otherwise overwhelming amount of data available nowadays from the web and the data collected every day by companies. Data Mining techniques can therefore be the keystone to reveal non-trivial knowledge expressed by the initial assumption used to build the micro-level of the model and the structure of the society of agents that emerged from the simulation
Excitation and time resolved spectroscopy of SAW harmonics up to GHz regime in photolithographed GaAs devices
No full textIn this work, we demonstrate the excitation of surface acoustic waves (SAW) harmonics up to GHz regime in photolitographed devices fabricated on gallium arsenide (GaAs) by acting on the IDT metallization ratio among the finger width and pitch. Specifically, we observed up to the 13th harmonic, which corresponds to a frequency of about 1.7 GHz. Moreover, we employed time-resolved spectroscopy for isolating the shape of the SAW bandpass-filter response (for each harmonic) eliminating the interference between acoustic and electromagnetic waves. Notably, the extracted SAW spectra are characterized by a bandwidth which remains constant for the different harmonic modes, unlike the case of traditional SAW filters (having a 0.5 metallization ratio) where the pass band Delta f = f(0)/n(p) np increases with the working frequency. These results are relevant for applications where high frequencies and multiple harmonics excitation are desirable, or where quantitative measurements of the direct SAW signal are required
Facades of the Libreria di San Marco in Venice, The: An Interpretation of the Design Process
No full text"A new work in which I propose an interpretation of the design process Sansovino used to create the magnificent facades of the Libreria di San Marco in Venice, a masterpiece of Renaissance architecture." Sent to Marquand librarian by author Dec. 202
Art without an Author: Vasari’s Lives and Michelangelo’s Death
No full textMonografia sulla rappresentazione di Michelangelo nelle due edizioni delle Vite, sulla storia del libro e la questione della sua paternitàBook dedicated to the representation of Michelangelo in Vasari's Lives of the Artists, to the history of the book, and to the problem of its authorshi
Frequency and time domain analysis of surface acoustic wave propagation on a piezoelectric gallium arsenide substrate: A computational insight
No full textA computational study of the electromechanical response of micro-structure engineered two port surface acoustic wave delay lines on gallium arsenide is presented. The influence on the results of geometrical, material, and mesh parameters is also discussed. Furthermore, experimental results are provided to validate the numerical study. The device consists of two interdigital transducers composed of 40, 80, and 120 pairs of electrodes, respectively, with a pitch pidt=8μm and distant didt=1502μm. In particular, a microwave burst of surface acoustic waves propagating on gallium arsenide is fully characterized including multiple transit effects. These results are of major interest for understanding the dynamical behavior of complex systems such as surface acoustic wave–based sensors or energy harvesting devices at the nano and microscale
Effects of the environment on quantum systems: decoherence, bound states and high impedance in superconducting circuits
Get PDFSuperconducting circuits in the quantum regime represent a viable platform for microwave quantum optics, quantum simulations and quantum computing. In the last two decades, a large effort brought this architecture from an academic curiosity to concrete technology.\ua0 In this thesis, we study the effects of the environment on superconducting circuits. We consider mainly two typologies of the environment. On one hand, we study the classical baths inevitably coupled to the circuits, in particular the substrate where they are fabricated and the highly attenuated coaxial lines used for controlling them, which are the main sources for decoherence. On the other hand, we study structured electromagnetic environments that shape the density of states for the circuits, modifying their energy structure and their excitation properties.\ua0\ua0 Defects on the substrate mechanically and electrically coupled to superconducting circuits, behave as a bath of two-level systems. We investigate the effects of the bath on a qubit fabricated on silicon. From a time trace with more than 2000 measurements of T1 and T2 (every 3 min for 60 h), we statistically infer a Lorentzian resonance signature of the bath. Moreover, measuring the residual population of the first excited state of the qubit, and tuning the photonic population in the line, we assess the thermal state of the bath, measuring a temperature of 56 mK. Furthermore, we investigate the mechanical coupling of the bath, saturating its state, strongly pumping neighbouring modes in a high finesse mechanical resonator. On a piezoelectric substrate, the travelling phonons, carry an electric component together with a lattice deformation. Therefore, superconducting circuits can be coupled to a phononic waveguide through which they release part of their energy. We design, fabricate and measure superconducting resonators on gallium arsenide, demonstrating the electromechanical coupling as the main source of decoherence.\ua0Concentrating on the effects of the photonic bath in the coaxial line, we design a qubit with a very large coupling to this bath compared to the bath of two-level fluctuators. In this limit, the scattering of a coherent photon by the qubit linearly depends on the photonic bath population. In this regime, the qubit can be used as a primary thermometer; we measured injected calibrated noise and the photon occupation of our input lines at different temperatures.\ua0 Finally, we implemented a slow-waveguide made of a linear chain of high impedance resonators. The excitation of two transmon qubits coupled to the waveguide is dressed with a photonic component, generating the hybrid excitation of atom-photon bound state. We spectroscopically investigated the first and second excitation subspaces of the system, and we demonstrated full frequency and time domain control, of these bound states. These results may help to improve the performance of superconducting circuits and their setup. Moreover, we hope that our experiment can provide tools for quantum thermodynamics and quantum simulation
How to prevent crimes using earthquakes
Get PDFIn this chapter the author describes how techniques coming from earthquakes prediction has been used to produce successful mathematical models useful in preventing crimes
Effects of the environment on quantum systems: decoherence, bound states and high impedance in superconducting circuits [Elektronisk resurs]
No full textSuperconducting circuits in the quantum regime represent a viable platform for microwave quantum optics, quantum simulations and quantum computing. In the last two decades, a large effort brought this architecture from an academic curiosity to concrete technology. In this thesis, we study the effects of the environment on superconducting circuits. We consider mainly two typologies of the environment. On one hand, we study the classical baths inevitably coupled to the circuits, in particular the substrate where they are fabricated and the highly attenuated coaxial lines used for controlling them, which are the main sources for decoherence. On the other hand, we study structured electromagnetic environments that shape the density of states for the circuits, modifying their energy structure and their excitation properties. Defects on the substrate mechanically and electrically coupled to superconducting circuits, behave as a bath of two-level systems. We investigate the effects of the bath on a qubit fabricated on silicon. From a time trace with more than 2000 measurements of T1 and T2 (every 3 min for 60 h), we statistically infer a Lorentzian resonance signature of the bath. Moreover, measuring the residual population of the first excited state of the qubit, and tuning the photonic population in the line, we assess the thermal state of the bath, measuring a temperature of 56 mK. Furthermore, we investigate the mechanical coupling of the bath, saturating its state, strongly pumping neighbouring modes in a high finesse mechanical resonator. On a piezoelectric substrate, the travelling phonons, carry an electric component together with a lattice deformation. Therefore, superconducting circuits can be coupled to a phononic waveguide through which they release part of their energy. We design, fabricate and measure superconducting resonators on gallium arsenide, demonstrating the electromechanical coupling as the main source of decoherence. Concentrating on the effects of the photonic bath in the coaxial line, we design a qubit with a very large coupling to this bath compared to the bath of two-level fluctuators. In this limit, the scattering of a coherent photon by the qubit linearly depends on the photonic bath population. In this regime, the qubit can be used as a primary thermometer; we measured injected calibrated noise and the photon occupation of our input lines at different temperatures. Finally, we implemented a slow-waveguide made of a linear chain of high impedance resonators. The excitation of two transmon qubits coupled to the waveguide is dressed with a photonic component, generating the hybrid excitation of atom-photon bound state. We spectroscopically investigated the first and second excitation subspaces of the system, and we demonstrated full frequency and time domain control, of these bound states. These results may help to improve the performance of superconducting circuits and their setup. Moreover, we hope that our experiment can provide tools for quantum thermodynamics and quantum simulation
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