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Laboratoire Matériaux et phénomènes quantiques (Paris)

Overview
Works: 37 works in 37 publications in 2 languages and 37 library holdings
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Most widely held works by Laboratoire Matériaux et phénomènes quantiques (Paris)
Magnetic anisotropy and spin crossover at molecule-metal interfaces by Kaushik Bairagi( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

The use of organic materials in spintronic devices has recently raised a lot of interest. Large spin diffusion time in organic materials along with the flexibility of manipulating the spin state of the molecule and their interaction with the ferromagnetic metal electrode offers new functionalities in molecular spintronics. Understanding the spin crossover (sco) phenomenon for spin active molecules attached to metallic substrate is also necessary for a primary step towards device application.The main goal of the thesis work was to study these molecule--metal interfaces. In one part, we have studied the magnetism of the organic--ferromagnetic interface with different molecules and different ferromagnetic metals. The study was mainly focused on the magnetic anisotropy at the molecule-metal interfaces. In other part, we focused on the spin crossover phenomena of sco molecules attached to metallic substrates. X--ray absorption spectroscopy and magnetic circular dichroism techniques enabled us to study globally the spin crossover phenomenon. Using scanning tunneling microscopy we were able to study the sco phenomena at the single molecular level in a 2d crystal of molecules on a metal substrate. We have then studied locally the dynamics of the spin transition phenomenon upon laser exposure on a single 2d layer molecular crystal
Emetteurs infrarouges superradiants by Sébastien Cosme( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

This thesis focuse on the realisation and the caracterisation of infrared emitters. They are based on the use of III-V, heavly doped, semiconductor layer. When the thickness of the semiconductor layer is less than the wavelenght of the plasmon inside the material, the plasmon is confined and strongly couple with the radiation. The absorption spectrums show a single resonance in the mid-infrared for our structure. The spontaneous emission rate of the plasmon is proportional to the electronic density of the semiconductor layer. The Spontaneous emission is therefore a cooperative phenomena : the confined plasmon is superradiant. In this thesis I use the equality between emissivity and absorptivity (kirchohoff law of emissivity), together with the strong coupling of the plasmon with the radiation, in order to realized thermal emitters in the mid-infrared. This emitters are narrow and directive. In the devices that I realized, the plasmon is thermally excited thanks to the injection of a current in the plane of the highly doped layer. The study and the imporvement of the emission properties of this device are the heart of this work. The main result that I obtain is the realisation of a thermal emitter that can be modulated up tu 50 MHz, which is two order of magnitude higher than the state of the art
Étude par STM de nanostructures métalliques dans le graphène : croissance, propriétés et défauts induits by Quentin Berrahal( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

Le graphène, premier cristal purement bidimensionnel à avoir été obtenu, possède des propriétés électroniques uniques grâce à sa structure de bande en « cône de Dirac ». Au-delà des modifications et du contrôle de ses propriétés intrinsèques, il est aujourd'hui crucial d'étudier ses interactions avec divers environnements afin de créer de nouvelles applications : fonctionnalisation par des molécules, utilisation en tant que substrat pour des molécules ou des atomes métalliques, création de défauts structuraux ou chimiques, élaboration de multicouches à l'aide d'autres matériaux quasi-bidimensionnels (hétérostructures de type Van der Waals)
All-dielectric nonlinear nanophotonics by Valerio flavio Gili( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

La méta-optique non linéaire tout diélectrique suscite un vif intérêt, grâce à la faisabilité de nanostructures à contraste élevé et indice de réfraction disponible avec la lithographie à semi-conducteurs. Alors que des effets nonlinéaires au troisième ordre ont été rapportés dans les nanoantennes silicium sur isolant, la plate-forme AlGaAs-sur-isolant a récemment permis la démonstration de la génération de la seconde harmonique, dû à la noncentrosymétrie de ce matériel. Cette thèse illustre notre activité récente sur les nanoantennes non linéaires AlGaAs-sur-AlOx, où AlOx est obtenu par attaque chimique sélective par voie humide d'une couche épitaxiale d'AlGaAs riche en aluminium d'une épaisseur de quelques micromètres. Un tel substrat à faible indice de réfraction permet de découpler efficacement les modes nanoantenna de la tranche de GaAs (100) sous-jacent. La thèse présente d'abord les méthodes numériques, expérimentales et technologiques utilisées. Une analyse des résultats obtenus dans la génération de signaux non linéaires dans des nanoantennes simples et dans des structures complexes est ensuite présentée. Tous nos résultats expérimentaux ouvrent la voie à la génération et à la manipulation de signaux non linéaires à l'échelle nanométrique et pointent vers des applications telles que l'holographie non linéaire, la goniométrie sans fond et la vision nocturne
Nanoscale in situ studies of Au and Au-Cu Nanoparticle synthesis by liquid cell transmission electron microscopy by Nabeel Ahmad( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

Recent years have seen a remarkable increase in research activities related to the synthesis of metallic nanocrystals. This intense interest is fueled by the unique and fascinating properties delivered at such size domains. Indeed, electrons confinement by nanocrystals is a powerful means to modulate electronic, optical and magnetic properties of a material. Most current strategies employ chemical synthesis to formulate unique nanoparticle morphologies by exploiting the versatility of liquid reaction media to control the formation mechanisms. Although the chemistry of metal nanocrystal synthesis is not complicated, understanding the nucleation and growth processes in complex liquid media and the influence of each chemical species is altogether a different challenge. It is in this regard, that we have utilized liquid cell transmission electron microscopy to visualize relevant growth phenomenon at the nanoscale. This recent in situ technique allowed us to study in real time the dynamics of growth of Au and Au-Cu nanoparticles in reaction media of controlled composition. The primary goal of this thesis was to distinguish the kinetics effects (related to the flow of matter) and the thermodynamics effects (related to the environment-dependent equilibrium of nanostructures) on final nanoparticle shapes. In addition to this, systematic studies were performed to separate the inevitable beam effects from the influence of specific synthesis parameters such as the seed crystal morphology and the organic functionalization that are of primary importance for colloidal chemists. Beam induced phenomena were also utilized to understand the solution chemistry of the exposed solvent which is in turn responsible for driving reversible redox reactions in bimetallic nano-systems
Anderson localization in interacting quantum systems by Filippo Stellin( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

In this thesis we theoretically investigate the behaviour of quantum particles (electrons, atoms, photons, etc.) moving in a random medium and undergoing Anderson localization. For noninteractingparticles, the energy spectrum can possess one or more critical points, where the nature of the single-particle wavefunctions changes from extended to localized leading to a undergoes a metal-insulator phase transition, also known as Anderson transition.A fundamental question is whether and how Anderson transitions survive in interacting quantum systems. Here we study a minimal model of two particles moving in a disordered lattice and subject to short-range mutual interactions. By combining large-scale numerics with Green's functions techniques, we show that two-particle Anderson transitions do occur in three dimensions and explore the phase diagram in the space of energy, disorder and interaction strength. The latter presents a rich structure, characterized by a doubly reentrant behavior, caused by the competition between scattering and bound states of the pair. We also show that previous claims of 2D Anderson transitions of the pair are essentially due to finite-size effects.A second problem that we address in this thesis is the occurrence of 2D metal-insulator transitions for a single particle in the presence of a spatially correlated potential and subject to spin-orbit interactions, described by Rashba-Dresselhaus couplings. We illustrate that, irrespective of the properties of the disorder, there is a regime where the critical energy depends linearly on the disorder strength. The slope and the intercept are studied in the vicinity of the spin-helix point, where the SU(2) symmetry is restored and the 2D metal-insulator transition disappears
Contextuality and nonlocality in continuous variable systems by Adrien Laversanne-Finot( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

Quantum mechanics has many intriguing properties that have no-classical analogs. These properties are at the heart of many quantum information protocols which offer the possibility to outperform their classical counterparts. This thesis is devoted to an investigation of two of the fundamental properties of quantum mechanics: non-locality and contextuality. The goal of this thesis is twofold. Firstly we will study how known results for discrete systems can be extended to continuous variables systems. Secondly, we will investigate how these properties can be tested in quantum systems characterized by continuous variables.Our work starts with an investigation of the set of local and no-signaling probability distributions. We develop a formalism for generic no-signaling black-box measurement devices with continuous outputs in terms of probability measures. We introduce the continuous-variable version of the famous Popescu-Rohrlich boxes and show that they violate the Tsirelson bound of an adequate continuous-variable Bell inequality. Finally, we perform a characterization of the geometry of the set of continuous-variable no-signaling correlations. More precisely, we show that the convex hull of those boxes is dense in the no-signaling set.We then study the contextuality of Quantum Mechanics in a state independent formulation. In particular, we study the Peres-Mermin state independent non-contextuality inequality, and show how it is possible to generalize the Peres-Mermin inequality to scenarios involving observables with an arbitrary number of outcomes. Specifically, we identify general conditions on the spectral decomposition of observables demonstrating state independent contextuality of quantum mechanics in this scenario.Lastly, we explore the non-local properties of entangled cat states, made of superpositions of coherent states stored in two spatially separated cavities. We show that even when taking into account the experimental imperfections such as the losses, a violation of local-realism is still possible, in the form of a violation of an appropriate Bell inequality
Phase transitions in light-matter systems for quantum sensing by Louis Garbe( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

When light and matter are weakly coupled, they can be described as two distinctive systems exchanging quanta of energy. By contrast, when their coupling strength becomes very large, the systems hybridize and form compounds that cannot be described in terms of light or matter only. In this Thesis, we will study some exotic properties which arise in this regime. In particular, we will be interested in the possibility to engineer quantum phase transitions in these systems. One direction we explore is the study of two-photon coupling, a mechanism in which photons are created or emitted in pairs. This mechanism creates a rich phase diagram containing both phase transitions and instabilities. Another point of interest is the possibility to use these transitions for sensing applications. Indeed, near the critical point, the system becomes extremely sensitive to external perturbations. We will present a protocol in which a single qubit coupled to a bosonic field. Despite its simplicity, this system displays a phase transition. Near the critical point, both the frequency of the qubit and the field can be measured with improved accuracy. Hence, finite-size transitions could be used to develop small-scale sensors. As last topic, we study how the ability of a system to perform certain metrological tasks could be used to characterize and quantify nonclassicality, by using the formalism of resource theories
Exploring thermoelectricity and electronic transport of molecular layers by Chloé Salhani( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

Progress in material science over the past half-century has been engaged in a constant race towards miniaturization. At the scales where quantum effects dominate the physics at play, molecular electronics has been considered a promising field of study, proposing to exploit quantum physics to achieve the desired functionality of a molecular device. In this thesis, I investigate electronic and thermoelectric properties of large-area solid-state molecular junctions, devices constructed of robust and covalently-grafted molecular layers formed by multiple molecular chains containing several molecular units in series contacted between metallic electrodes. A first part of this thesis concerns the investigation of inelastic el-ph interactions in layers of anthraquinone (AQ). The AQ molecule exhibits quantum interference (QI) effects, causing an extinction of the transmission function (and thus the conductance) near the zero-bias point and thus enhancing the visibility of inelastic effects (el-ph interactions). IETS spectroscopy is performed on these layers and allows to identify known vibrational modes of the AQ molecule. A second part of this work investigates the thermoelectric properties of similar molecular layers (using AQ, BTB and NB molecules). Engineering challenges are met with the development of a new sample geometry using an AuGe thin-film alloy as a heater-thermometer element, to enable establishing a controlled temperature gradient across the thickness of the molecular layer (~15nm). Finally, I explore the presence of a thermoelectric potential developed across the molecular layer. A third and final part of this thesis explores a new geometry for large area molecular junctions. Instead of a bottom-up approach, nanotrenches are used to fabricate in-plane molecular junctions in a geometry designed to allow gate integration at a later stage. I present the fabrication of these nanotrenches using a shadow-edge mask method, and their characterization before and after molecular grafting. AQ-grafted nanotrenches reveal typical transport signatures of molecular junctions that are compared to the behavior of the more standard planar fabrication
Etude structurale d'interfaces organiques/métalliques avec propriétés magnétiques by Cynthia Fourmental( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

The aim of this thesis is to study at micrometric scale and nanoscale the structure of materials of interest for organic spintronics, focusing in particular on two crucial aspects to obtain good devices quality: molecular/metal interfaces and organic layers. In order to compare our results with theoretical predictions, we have used metallic single crystals and molecular deposition under ultra-high vacuum, allowing the obtention of high quality samples. We focused our study on two systems, one based on C60 and Cobalt and the other based on spin crossover molecules and Gold.To elucidate the structure of our samples, we used scanning tunneling microscopy and X-ray scattering, two techniques that are complementary, one probing the local organization and the other the global otganization of the system. The results obtained were compared to ab initio calculations carried out on the same systems. Regarding the deposition of C60 molecules on a Co (0001) substrate, we have been able to demonstrate that the annealing of the sample leads to a structural transition of the interface, with the creation of Cobalt vacancies under each molecules, forming a periodic network. Before annealing, the molecular layer also exhibits high crystallinity. The Cobalt deposition on this molecular crystal causes a contraction of the lattice, due to Cobalt diffusion into interstitial sites. Finally, concerning the [FeII (HB (3,5- (CH3) 2Pz) 3) 2] spin-crossover complex deposited on Au (111), we have demonstrated an unexpected epitaxial relationship between the molecular lattice and the substrate
Thermodynamique de surface et réactivité du nanoalliage CU-AU par microscopie électronique en transmission environnementale en condition gazeuse by Adrian Chmielewski( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

Le nanoalliage cuivre-or (CuAu) pour la catalyse hétérogène fait l'objet d'un intérêt grandissant de la communauté scientifique. En effet, l'alliage de l'or, réputé être un élément stabilisateur, avec le cuivre, réputé très actif notamment vis-à-vis de l'oxygène, offre de très grandes possibilités, tant dans les réactions d'oxydation tel que l'oxydation du monoxyde de carbone, mais aussi dans les réactions d'hydrogénation, telle que l'hydrogénation sélective du butadiène. L'un des processus déterminant dans les réactions d'oxydation et d'hydrogénation est le processus d'adsorption et de dissociation des molécules d'O2 et de H2 par le catalyseur. Afin d'avoir une meilleure compréhension des processus mis en jeu, il est nécessaire d'identifier les sites actifs où a lieu l'adsorption et la dissociation éventuelle des molécules, mais aussi des mécanismes mis en jeu lors de ces processus. Mais aujourd'hui, il n'existe pas de consensus général, dans la communauté scientifique, concernant la localisation des sites actifs. C'est dans ce contexte que s'inscrit ce travail de thèse, mené au laboratoire Matériaux et Phénomènes Quantiques (MPQ) au sein de l'équipe Microscope électronique Avancée et NanoStructures (Me-ANS) dirigé par le professeur Christian Ricolleau. Les deux problématiques majeures auxquelles nous nous sommes intéressées sont (i) la stabilité structurale et morphologique des nanoparticules de Cu, Au et de Cu-Au dans le vide et en température et ce sur différents supports tels que le nitrure de silicium amorphe et le rutile-TiO2, (ii) la stabilité structurale et morphologique des nanoparticules de Cu, Au et de Cu-Au supportées sur rutile-TiO2, sous atmosphère de gaz oxydant (O2) et réducteur (H2). Les objectifs étant d'identifier les sites d'adsorption éventuels des molécules d'O2 et de H2 par les catalyseurs, et de mieux comprendre les mécanismes qui conduisent à l'évolution morphologique de ceux-ci en milieu réactif
Characterization and applications of quantum measurement invasiveness by Saulo Vicente Moreira( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

L'invalidité de la mesure quantique est une propriété des phénomènes quantiques.Elle est reliée au fait que la mesure de systèmes quantiques peut les affecter d'une façon que ne peut pas être décrite au sein de la physique classique.Cette thèse étudie la question de l'invasivité des mesures quantiques à travers l'inégalité de Leggett-Garg et d'une autre inégalité basée sur la condition de non perturbation (\ non-disturbance condition "). La violation de ces inégalités témoigne de l'invasivité des mesures quantiques. Dans un premier temps, nous _étudierons un modèle pour la violation de l'inégalité de Leggett-Garg, qui permettra une caractérisation opérationnelle de l'invasivité de la mesure quantique à travers un paramètre appelé la mesurabilité du système physique. Ce paramètre contrôle la violation de l'inégalité de Leggett-Garg et peut être reliée à des tests expérimentaux de cette inégalité. De cette façon, ce paramètre permet la compréhension et l'interprétation de ces violations. Nous avons également étudie, via ce modèle, la relation entre l'invasivité et une définition particulière de la « macroscopicité", associée la »taille " de systèmes de spin. Nous avons ensuite étudie une application de l'invasivité de la mesure quantique dans le cadre des protocoles pour l'estimation de paramètres en métrologie quantique. Une relation générale entre l'information de Fisher et les corrélations quantiques temporelles a été établie, et permet la caractérisation de la robustesse au bruit de scenarios de métrologie. Cette relation sert de ligne directrice pour la connexion entre l'invasivité de la mesure quantique et des scenarios (quasi-)optimaux en métrologie. Nous avons également établi une relation entre l'invasivité de la mesure quantique et une définition de la cohérence macroscopique. Pour finir, nous avons proposé un protocole pour tester la non-invasivité de mesures, basé sur la condition de non perturbation, pour des systèmes de spin de taille arbitraire. Cette inégalité permet de s'assurer contre la possibilité que sa violation soit due à des perturbations classiques de la mesure. Nous avons montré que la valeur maximale pour la violation de l'inégalité correspond au nombre de particules qui constitue le système
Supraconductivité et ordres exotiques : à la recherche du Boson de Higgs by Romain Grasset( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

En 1980, une excitation électronique inédite des électrons supraconducteurs a été mise en évidence par spectroscopie Raman dans le composé 2H-NbSe2. Cette excitation semble pouvoir être associée à un mode collectif d'amplitude du paramètre d'ordre supraconducteur.Ce mode, analogue au boson de Higgs dans le modèle standard, est normalement non couplé à la lumière mais serait observable dans le cas de 2H-NbSe2 via un couplage de la supraconductivité avec une autre phase exotique appelée onde de densité de charge.Cette thèse a consisté à utiliser la spectroscopie Raman sous haute pression pour mettre cette théorie à l'épreuve de deux façons. D'une part, en détruisant l'onde de densité de charge dans 2H-NbSe2 sous haute pression et voir si celle-ci est réellement nécessaire à l'observation du mode Higgs. D'autre part, en cherchant de nouveaux exemples d'observation du mode de Higgs dans d'autres composés (2H-TaS2, 2H-TaSe2,...) où la supraconductivité coexiste avec une onde de densité de charge
Quantum interference and thermoelectric effects in molecular junctions by Charlotte Bessis( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

This thesis reports the transport measurement performed on large scale solid state molecular junctions, highlighting quantum interference effect. First chapter set the theoretical basis of such a phenomenon and introduces the out of equilibrium green's functions formalism which is adapted to the description of coupling molecules/metallic interfaces. Second chapter presents the corresponding experimental state of the art and summarizes the experiments that have contributed to highlight interference effect at the molecular scale. Third chapter describes the fabrication steps optimized to build the devices measured during the thesis work. Experimental results obtained on conductance measurements are described and compared to several theoretical models that confirm the presence of quantum interference. Last chapter deals with thermoelectric effect that can occur in presence of interference
Spectroscopie Raman du supraconducteur FeSe by Pierre Massat( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

La découverte en 2008 des supraconducteurs à base de fer a ouvert un nouveau champ d'investigation de la supraconductivité à haute température critique. En particulier, la phase nématique de ces matériaux pourrait jouer un rôle prépondérant dans le mécanisme de la supraconductivité. Nous avons étudié le composé FeSe par spectroscopie Raman, à pression ambiante et sous pression hydrostatique. Celui-ci ne possède pas d'ordre magnétique statique à pression ambiante, ce qui en fait un composé de choix pour l'étude de l'ordre nématique. Nous avons observé les fluctuations nématiques de charge. Leur évolution dans la phase tétragonale prouve l'existence d'une instabilité nématique d'origine électronique, qui gouverne la transition structurale. Dans la phase orthorhombique, le comportement des phonons souligne le rôle du couplage spin-phonon dans la transition nématique. Par ailleurs, la forme de la réponse Raman supraconductrice est compatible avec l'existence de deux gaps de symétrie s, dont un est anisotrope. Sous pression hydrostatique, les fluctuations nématiques s'atténuent rapidement. Le point critique quantique électronique associé se situe à très basse pression, peu avant l'apparition de l'ordre magnétique. Les fluctuations nématiques disparaissent complètement vers 2 GPa, quand la transition structurale passe de second ordre à premier ordre. C'est également proche de cette pression que se produit une anomalie dans le comportement des phonons, qui indique une modification de la structure électronique du système. Nos mesures révèlent en outre l'existence d'un pseudogap. Sa température d'apparition chute simultanément à la disparition de la phase magnétique, quand la température critique de supraconductivité atteint son maximum. Enfin, la réponse Raman de l'état supraconducteur à 7.8 GPa montre une signature claire d'un gap plein
Surface-enhanced optomechanical disk resonators and force sensing by Biswarup Guha( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

Optomechanics studies the interaction between light and mechanical motion. This PhD thesis reports on optomechanical experiments carried with miniature disk resonators fabricated out of distinct III-V semiconductors: Gallium Arsenide (GaAs), Aluminium Gallium Arsenide (AlGaAs) and Indium Gallium Phosphide (InGaP). These materials are compliant with optoelectronics functionalities and provide giant optomechanical coupling. In order to boost performances of GaAs resonators, we implemented surface control techniques and obtained a ten-fold reduction of optical dissipation, attaining a Q of six million. On top of GaAs, we performed a comparative investigation of optomechanical interactions in InGaP and AlGaAs disk resonators, and demonstrated their operation as optomechanical oscillators. Finally, we carried out optomechanical force sensing experiments with GaAs resonators, analyzing a new sensing principle in light of the phase space trajectory and phase noise of the corresponding oscillators
Quantum Measurement and Feedback Control of highly nonclassical Photonic States by Jared Lolli( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

In recent years, the field of quantum optics has thrived thanks to the possibility of controlling light-matter interaction at the quantum level.This is relevant for the study of fundamental quantum phenomena, the generation of artificial quantum systems, and for quantum information applications.In particular, it has been possible to considerably increase the intensity of light-matter interaction and to shape the coupling of quantum systems to the environment, so to realise unconventional and highly nonclassical states.However, in order to exploit these quantum states for technological applications, the question of how to measure and control these systems is crucial.Our work is focused on proposing and exploring new protocols for the measurement and the control of quantum systems, in which strong interactions and peculiar symmetries lead to the generation of highly nonclassical states.The first situation that we consider is the ultrastrong coupling regime in cavity (circuit) quantum electrodynamics.In this regime, it becomes energetically favourable to have photons and atomic excitations in the ground state, that is no more represented by the standard vacuum.In particular, in case of parity symmetry, the ground state is given by a light-matter Schrödinger cat state.However, according to energy conservation, the photons contained in these exotic vacua are bound to the cavity, and cannot be emitted into the environment.This means that we can not explore and control them by simple photodetection.In our work we propose a protocol that is especially designed to overcome this issue.We show that we can infer the photonic properties of the ground state from the Lamb shift of an ancillary two-level system.Another class of systems in which the fundamental parity symmetry leads to very unconventional quantum states is given by two-photon driven-dissipative resonators.Thanks to the reservoir engineering, it is today possible to shape the interaction with the environment to stabilize the system in particularly interesting quantum states.When a resonator (an optical cavity) exchanges with the environment by pairs of photons, it has been possible to observe the presence of optical Schrödinger cat states in the transient dynamics of the system.However, the quantum correlations of these states quickly decays due to the unavoidable presence of one-photon dissipation.Protecting the system against this perturbation is the goal of the parity triggered feedback protocol that we present in this thesis
Vers l'optomécanique quantique en arséniure de gallium : dissipation nanomécanique et opération pulsée by Mehdi Hamoumi( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

Synthèse et étude des propriétés structurales thermodynamiques et catalytiques de nanoparticules bimétalliques Au-Cu par microscopie électronique en transmission corrigée d'abérrations by Hélène Prunier( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

The emergence of new materials, structured at the nanoscale, with controlled properties, has opened new prospects regarding materials around us. In particular for metals and alloys, it seems crucial to connect their structural properties to their chemical and physical properties in order to optimise their use.Within this context, this thesis is focused on the synthesis and the characterisation of Au-Cu bimetallic alloy nanoparticles by transmission electron microscopy. On the basis of the bulk phase diagram, we especially studied particles with nominal compositions Au3Cu, AuCu et AuCu3.The first part of this work is dedicated to the synthesis of nanoparticles in two different ways. The chemical way is based on the polyol process and leads to nanoparticles exhibiting a cubic shape, and a systematically rich Au content. On the other hand, nanoparticles obtained by Pulsed Laser Deposition (PLD), a physical method of synthesis, display a well-controlled and tuneable composition. From a structural point of view, the annealing of the particles leads to chemical order and the stabilisation of L10 and L12 structures. However, we reveal that this phase transition is blocked in nanostructures with crystal defects. Moreover, we establish the evolution of the lattice parameter of the particles as a function of the composition and we demonstrate that, as in the bulk case, it is in agreement with Vegard's law.In the second part, the nanoparticles synthesised via the physical method are studied using environmental transmission electron microscopy, i.e. in conditions close to those usually applied in catalytic reactors. Experiments performed at high temperature highlight that the dissolution of Au and Au-Cu nanoparticles occurs in a two-step process: fusion occurs first and is followed by evaporation for nanoparticles with a mean diameter of 10 nm.Coupling heating with gas flow (H2 or O2) in higher pressure condition than those usually reached allows us to study the thermodynamic behaviour of the nanoparticles in oxidative or reductive conditions. Most Notably, we show that oxidation-reduction cycles performed on nanoparticles with a diameter larger than 20 nm leads to a Kirkendall effect and the reversible formation of hollow particles (doughnuts).This cross-disciplinary thesis is a pioneering work towards understanding the bimetallic Au-Cu alloy system at atomic scale
Generation and manipulation of high-dimensional photonics states with AlGaAs chips by Giorgio Maltese( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

This thesis is devoted to the development of novel integrated semiconductor devices and methods for the generation and manipulation of high-dimensional states of light. We report on the study of an AlGaAs waveguide implementing type-II spontaneous parametric down conversion process in a monochromatic pump regime, with a focus on the joint spectral amplitude of the emitted biphoton state. The source works at room temperature, emits photon pairs in the telecom range and is compliant with electrical injection. The generation of broadband biphoton states is experimentally demonstrated via the reconstruction of the joint spectral intensity and via a Hong-Ou-Mandel experiment indicating that signal and idler photons are emitted over a large bandwidth (170nm) and with a high degree of indistinguishability (V=0.86). Moreover, we show that the cavity effect due to waveguide facets reflectivity leads to the production of biphoton frequency-comb states. This platform is used to demonstrate an original method to generate and control the symmetry of biphoton frequency combs exploiting cavity effects and a delay between the two photons of each pair. More specifically, we show that a fine tuning of the pump frequency enables the generation of resonant and anti-resonant comb states allowing to manipulate the wavefunction symmetry. The method can be adapted and applied to a large variety of systems, either bulk or integrated, thus increasing their flexibility and the richness of the generated states in view of implementation of new quantum information protocols.In addition, we demonstrate the realization of an AlGaAs ridge waveguide for the generation of light beams with tailored phase and polarization distributions, carrying spin angular momentum, and present the design of a device for the generation of a twisted light beam, carrying first order orbital angular momentum
 
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Alternative Names
Centre national de la recherche scientifique (France). Laboratoire Matériaux et Phénomènes Quantiques

Centre national de la recherche scientifique (France). Unité mixte de recherche (7162)

Laboratory Materials and Quantum Phenomena facility in Paris, France

MPQ

UMR 7162

UMR7162

Université Paris Diderot - Paris 7. Laboratoire Matériaux et Phénomènes Quantiques

Université Paris Diderot - Paris 7. Unité mixte de recherche (7162)

Languages
English (12)

French (8)