Bibliographies thématiques / Quantum mixture

Littérature scientifique sur le sujet « Quantum mixture »

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Publié le 10 mars 2023

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Articles de revues sur le sujet "Quantum mixture"

Magann, Alicia B., Gerard McCaul, Herschel A. Rabitz et Denys I. Bondar. « Sequential optical response suppression for chemical mixture characterization ». Quantum 6 (20 janvier 2022) : 626. http://dx.doi.org/10.22331/q-2022-01-20-626.

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The characterization of mixtures of non-interacting, spectroscopically similar quantum components has important applications in chemistry, biology, and materials science. We introduce an approach based on quantum tracking control that allows for determining the relative concentrations of constituents in a quantum mixture, using a single pulse which enhances the distinguishability of components of the mixture and has a length that scales linearly with the number of mixture constituents. To illustrate the method, we consider two very distinct model systems: mixtures of diatomic molecules in the gas phase, as well as solid-state materials composed of a mixture of components. A set of numerical analyses are presented, showing strong performance in both settings.

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SAARELA, MIKKO, et TAUNO TAIPALEENMÄKI. « QUANTUM FLUID MIXTURES IN DIFFERENT PHASES ». International Journal of Modern Physics B 17, n^o 28 (10 novembre 2003) : 5227–42. http://dx.doi.org/10.1142/s0217979203020375.

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Variational theory of quantum fluid mixtures is presented with the emphasis on the stability and phase transitions. We give results on two systems where new interesting phases are predicted. Dilute mixtures of 3 He impurities in the liquid 4 He in two dimensions form loosely bound pairs, dimers. The binding energy of the dimer ranges from milli- to micro-Kelvins with increasing 4 He density. The dimerised mixture of 3 He atoms is stable up to maximum solubility of ≈3%. Electrons and holes in semiconductors form a homogeneous mixture, electron-hole liquid. We predict that at low densities this system becomes unstable against clustering of charges and a liquid phase with a mixture of bound charged clusters could be formed.

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Sundaram S, Vasanthi T, Jayaprakash T, Balasubramanian V et Vijayakumar V N. « Optical and thermal studies on binary liquid crystal mixture ». Nanoscale Reports 4, n^o 1 (30 avril 2021) : 40–51. http://dx.doi.org/10.26524/nr.4.7.

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The novel binaryliquid crystal mixture is designed and synthesized from 4-methoxycinnamic acid (MCA) and 4-ethoxycinnamic acid (ECA). Quantum chemical (DFT) calculation for MCA+ECA geometry is optimized by DFT/B3LYP with 6-311G (d, p) basis set and its results are good agreement with experimental data. Fourier-transform infrared spectroscopic(FT-IR) study confirm the presence of intermolecular hydrogen bond in the liquid crystal mixture .The paramorphic changes in nematic phase and thermo-optic properties of binary liquid crystal mixture isanalyzed using polarizing optical microscope (POM) and differential scanning calorimetry (DSC) techniques. A noteworthy observation in the present liquid crystal mixture possesses smectic A phase along with nematic phases. Intermolecular hydrogen bond interaction and it’s stabilization energy of present mixture is studied by natural bond orbital (NBO) analysis. Due to the transition,the presen tliquid crystal mixtur einduces smecticA phase. The molecular properties of presen t binary liquid crystal mixtureis analyzed by HOMO-LUMO and experimental UV-Visible studies. Thermal spanwidth, stability factor and quantum chemical properties of the liquid crystal mixture are calculated.Molecular electrostatic potential, mulliken atomic charge distribution of the optimized MCA+ECA geometry is also reported.

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ROGERS, CAROLINE, et RAJAGOPAL NAGARAJAN. « LOSSLESS QUANTUM DATA COMPRESSION AND QUANTUM KOLMOGOROV COMPLEXITY ». International Journal of Quantum Information 09, n^o 02 (mars 2011) : 637–50. http://dx.doi.org/10.1142/s0219749911007848.

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We show that the optimal rate of lossless quantum data compression is closely related to Berthiaume, van Dam and Laplante's quantum Kolmogorov complexity. We show that: • The expected quantum Kolmogorov complexity of a mixture is close to the optimal rate of lossless data compression of that mixture. • If quantum Kolmogorov complexity obeys some inequality, then so does the optimal rate of lossless quantum data compression.

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Wichert, Andreas. « Quantum-like Gaussian mixture model ». Soft Computing 25, n^o 15 (11 juin 2021) : 10067–81. http://dx.doi.org/10.1007/s00500-021-05941-9.

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Susumu, Kimihiro, H. Tetsuo Uyeda, Igor L. Medintz et Hedi Mattoussi. « Design of Biotin-Functionalized Luminescent Quantum Dots ». Journal of Biomedicine and Biotechnology 2007 (2007) : 1–7. http://dx.doi.org/10.1155/2007/90651.

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We report the design and synthesis of a tetraethylene glycol- (TEG-) based bidentate ligand functionalized with dihydrolipoic acid (DHLA) and biotin (DHLA—TEG—biotin) to promote biocompatibility of luminescent quantum dots (QD's). This new ligand readily binds to CdSe—ZnS core-shell QDs via surface ligand exchange. QDs capped with a mixture of DHLA and DHLA—TEG—biotin or polyethylene glycol- (PEG-) (molecular weight average∼600) modified DHLA (DHLA—PEG600) and DHLA—TEG—biotin are easily dispersed in aqueous buffer solutions. In particular, homogeneous buffer solutions of QDs capped with a mixture of DHLA—PEG600 and DHLA—TEG—biotin that are stable over broad pH range have been prepared. QDs coated with mixtures of DHLA/DHLA—TEG—biotin and with DHLA—PEG600/DHLA—TEG—biotin were tested in surface binding assays and the results indicate that biotin groups on the QD surface interact specifically with NeutrAvidin-functionalized microtiter well plates.

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Mancini, S., et P. Tombesi. « Entanglement and nonlocality for a mixture of a pair-coherent state ». Quantum Information and Computation 3, n^o 2 (mars 2003) : 106–15. http://dx.doi.org/10.26421/qic3.2-2.

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We consider a bipartite continuous variables quantum mixture coming from phase randomization of a pair-coherent state. We study the nonclassical properties of such a mixture. In particular, we quantify its degree of entanglement, then we show possible violations of Bell's inequalities. We also consider the use of this mixture in quantum teleportation. Finally, we compare this mixture with that obtained from a pair-coherent state by single photon loss.

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Parks, A. D., S. E. Spence et J. E. Gray. « Exact pointer theories for von Neumann projector measurements of pre- and postselected and preselected-only quantum systems : statistical mixtures and weak value persistence ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 470, n^o 2162 (8 février 2014) : 20130651. http://dx.doi.org/10.1098/rspa.2013.0651.

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Exact expressions for the mean pointer position, the mean pointer momentum and their variances are obtained for projection operator measurements performed upon ensembles of pre- and postselected (PPS) and preselected-only (PSO) quantum systems. These expressions are valid for any interaction strength which couples a measurement pointer to a quantum system, and consequently should be of general interest to both experimentalists and theoreticians. To account for the ‘collapse’ of PPS states to PSO states that occurs as interaction strength increases and to introduce the concept of ‘weak value persistence’, the exact PPS and PSO pointer theories are combined to provide a pointer theory for statistical mixtures. For the purpose of illustrating ‘weak value persistence’, mixture weights defined in terms of the Bhattacharyya coefficient are used and the statistical mixture theory is applied to mean pointer position data associated with weak value projector measurements obtained from a recent dynamical quantum non-locality detection experiment.

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Gutierrez, Emmanuel Mercado, Gustavo Alves de Oliveira, Kilvia Mayre Farias, Vanderlei Salvador Bagnato et Patricia Christina Marques Castilho. « Miscibility Regimes in a 23Na–39K Quantum Mixture ». Applied Sciences 11, n^o 19 (29 septembre 2021) : 9099. http://dx.doi.org/10.3390/app11199099.

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The effects of miscibility in interacting two-component classical fluids are relevant in a broad range of daily applications. When considering quantum systems, two-component Bose–Einstein condensates provide a well-controlled platform where the miscible–immiscible phase transition can be completely characterized. In homogeneous systems, this phase transition is governed only by the competition between intra- and inter-species interactions. However, in more conventional experiments dealing with trapped gases, the pressure of the confinement increases the role of the kinetic energy and makes the system more miscible. In the most general case, the miscibility phase diagram of unbalanced mixtures of different atomic species is strongly modified by the atom number ratio and the different gravitational sags. Here, we numerically investigate the ground-state of a 23Na–39K quantum mixture for different interaction strengths and atom number ratios considering realistic experimental parameters. Defining the spatial overlap between the resulting atomic clouds, we construct the phase diagram of the miscibility transition which could be directly measured in real experiments.

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Polyukhin, A. S. « Modelling of the Thermodynamic Properties of the Plasma Mixture ». Nelineinaya Dinamika 17, n^o 1 (2021) : 49–57. http://dx.doi.org/10.20537/nd210105.

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Numerical modelling of the thermodynamic properties of plasma mixture is performed using the Thomas – Fermi model with two different approaches. For this purpose, a numerical algorithm, as well as program realization, is developed to solve the Thomas – Fermi equations with quantum-exchange corrections. For the first time a comparison between different methods for taking account of the heterogeneous composition of plasma is made and an algorithm for estimating the corrections for mixtures is developed.

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Thèses sur le sujet "Quantum mixture"

McCarron, Daniel John. « A quantum degenerate mixture of ⁸⁷Rb and ¹³³Cs ». Thesis, Durham University, 2011. http://etheses.dur.ac.uk/3242/.

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This thesis reports the formation of a dual-species Bose-Einstein condensate of ⁸⁷Rb and ¹³³Cs in the same trapping potential. Quantum degenerate mixtures exhibit rich physics inaccessible to single species experiments and provide an ideal starting point for the creation of ultracold dipolar molecules. These molecules offer a wealth of new research avenues including precision metrology, quantum simulation and computation. The experimental method exploits the efficient sympathetic cooling of ¹³³Cs via elastic collisions with ⁸⁷Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. Evaporative cooling in the dipole trap must compete against a high interspecies three-body inelastic collision rate ~ 10⁻²⁵ - 10⁻²⁶ cm⁶/s. The two condensates each contain up to 2 x 10⁴ atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the ⁸⁷Rb during the cooling leads to the creation of single-species ¹³³Cs condensates of up to 6 x 10⁴ atoms. In addition this thesis reports the observation of an interspecies Feshbach resonance at 181.7(5)G and the creation of a pure sample of Cs₂ molecules via magneto-association on the 4(g)4 resonance at 19.8 G. These results represent important steps towards the creation of ultracold polar RbCs molecules.

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Voigt, Arne-Christian. « Heteronuclear Molecules from a Quantum Degenerate Fermi-Fermi Mixture ». Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-106171.

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Taglieber, Matthias. « Quantum degeneracy in an atomic fermi-fermi-bose mixture ». Diss., kostenfrei, 2008. http://edoc.ub.uni-muenchen.de/8452/.

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Cabrera, Córdova César Raymundo. « Quantum liquid droplets in a mixture of Bose-Einstein condensates ». Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/663331.

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In this thesis, we report on the design and construction of a quantum simulator experiment using quantum gases in Spain. This experiment exploits mixtures of the three isotopes of potassium, which give access in an original approach to the study of Bose-Bose or Bose-Fermi mixtures using the same experimental setup. We validate our experimental setup with the observation of a Bose-Einstein condensate (BEC) of 41K and 39K. Moreover we observe the dual Bose-Einstein condensation of 39K–41K. These results represents the first observation of BECs in Spain and give access to a novel quantum degenerate mixture in the field. Since the control of interactions in our experiment are crucial, we characterize the scattering properties of the 39K–41K mixture, and spin mixtures of 39K and 41K. In addition, using a spin mixture of 39K BEC, we report on the observation of a novel state of matter: a composite quantum liquid droplet. This dilute quantum droplet is a liquid-like cluster of ultra-cold atoms self-trapped by attractive mean-field forces and stabilized against collapse by repulsive beyond mean-field many-body effects. This system follows the original proposal where D. Petrov predicted the formation of self-bound liquid droplets in mixtures of Bose-Einstein condensates. In the first series of experiments, we have observed the formation of quantum droplets in a regime where the Bose-Bose mixture should collapse from the mean-field perspective.We directly measure the droplet size and ultra-low density via high-resolution in situ imaging, and experimentally confirm their self-bound nature.We demonstrate that the existence of these droplets is a striking manifestation of quantum fluctuations. These droplets do not exist in single-component condensates with described with contact interactions. Finally, we observe that for small atom numbers, quantum pressure dissociates the droplets and drives a liquid-to-gas transition, which we map out as a function of interaction strength. These measurements open an intriguing point of investigation: the difference existing between droplets and bright solitons. In the second series of experiments, we address it by placing the mixture in an optical waveguide, realizing a system that contains both composite bright solitons and quantum liquid droplets. In analogy to non-linear optics, the former can be seen as one-dimensional matter-wave solitons stabilized by dispersion, whereas the latter corresponds to highdimensional solitons stabilized by a higher order non-linearity. We find that depending on atom number, interaction strength and confinement, solitons and droplets can be smoothly connected or remain distinct states coexisting only in a bi-stable region. We measure their spin composition, extract their density for a broad range of parameters, and map out the boundary of the region separating solitons from droplets. Our experiments demonstrate a novel type of ultra-dilute quantum liquid, stabilized only by contact interactions. They provide an ideal platform for benchmarking complex quantum many-body theories beyond the mean-field approximation in a quantum simulation approach. Furthermore, they constitute a novel playground to explore experimentally self-bound states stabilized by unconventional higher order nonlinearities, relevant in non-linear optics.
En este trabajo de tesis se reporta el diseño y la construcción de uno de los experimentos pioneros en España que permite realizar simulaciones cuánticas usando átomos ultra fríos. En este experimento se enfrían hasta alcanzar la degeneración cuántica los tres diferentes isotopos de potasio los cuales permiten, de manera particular y original, el estudio de mezclas cuánticas degeneradas de tipo Bose-Bose o Bose-Fermi. El funcionamiento del experimento es validado por medio de la producción de condensados de Bose-Einstein de 41K y 39K. Además, se reporta la condensación de la mezcla degenerada 41K - 39K, la cual no había sido previamente reportada en la literatura. Estos resultados son los primeros de su tipo en España y por lo tanto abren un amplio panorama en el estudio de fenómenos cuánticos en el país. La mezcla cuántica reportada en esta tesis permite acceder a sistemas cuánticos novedosos en el campo de átomos fríos. El control de las interacciones atómicas es una herramienta ampliamente usada en el campo, por lo cual se han caracterizado las propiedades de dispersión en esta nueva mezcla, así como en diferentes mezclas de espín entre los isotopos 41K y 39K. El resultado más importante de esta tesis reside en la creación de un nuevo estado de la materia: una gota liquida cuántica ultra-diluida. Esta gota cuántica se compone de una mezcla de dos estados diferentes de espín de 39K. Este líquido se encuentra ligado por sí mismo debido a la compensación de las fuerzas atractivas de campo con el carácter repulsivo de efectos cuánticos que van más allá de la aproximación de campo medio. Este sistema sigue la idea original de D. Petrov, esta propone la formación de líquidos cuánticos usando mezclas de condensados de Bose-Einstein. En la primera serie de experimentos, hemos observado la formación de gotas cuánticas en un régimen donde una mezcla de Bose debería de colapsar de acuerdo con teorías de campo medio. Se ha medido su tamaño y ultra-baja densidad por medio de imágenes in situ. De esta manera confirma cómo este líquido permanece ligado por si mismo en la ausencia de confinamiento externo. Hemos demostrado que la existencia de estas gotas cuánticas se debe a una manifestación sorprendente de las fluctuaciones cuánticas. Finalmente hemos observado cómo debido a la presencia de la presión cuántica, debajo de un numero critico de átomos el sistema se disocia en gas dando lugar a una transición cuántica liquido-gas. Esta transición se ha medido experimentalmente como función de las interacciones atómicas entre los átomos. Estas mediciones traen consigo una pregunta intrigante: ¿Cuál es la diferencia entre nuestras gotas cuánticas y los ya conocidos solitones de materia? En una segunda serie de experimentos, hemos dado respuesta a esta interrogante al estudiar las propiedades de una mezcla de Bose confinada en una guía óptica. En este tipo de geometría ambos estados pueden existir. En analogía a sistemas ópticos no-lineales, solitones son sistemas estabilizados por efectos de dispersión, mientras las gotas cuánticas corresponden a solitones de más alta dimensión estabilizadas por efectos no lineales de alto orden. Hemos encontrado que, dependiendo del número de átomos, fuerza de interacción y confinamiento, solitones y gotas cuánticas son dos estados cuánticos que pueden estar conectados, permanecer como dos estados distintos, o coexistir en una región de bi-estabilidad. Se ha medido su composición de espín, densidad del sistema y encontrado experimentalmente la frontera que separa ambos sistemas. En conclusión, los experimentos mostrados en esta tesis demuestran la existencia de un nuevo liquido cuántico ultra-diluido estabilizado únicamente por interacciones de contacto. Su existencia es puramente debida a las fluctuaciones cuánticas presentes en el sistema. Este sistema provee una plataforma ideal para el estudio y la comprensión de teorías cuánticas más complejas las cuales van más allá de la aproximación de campo medio.

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D'Alberto, Jacopo. « Study of a 2D Bose-Fermi mixture with quantum Monte Carlo methods ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24393/.

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Ultracold gases are an exceptionally versatile platform to test novel physical concepts. Thanks to the development of new experimental techniques, they have greatly advanced our understanding of the physics of many-body systems and allowed precision measurements of fundamental constants. Bose-Fermi mixtures can then be introduced in this context. This novel quantum many-body system is essentially an ultracold gas made up by both bosons and fermions, where tunable attractive or repulsive interactions between the components can be introduced. At T = 0 and for weak interactions the bosons condense while the fermions behave as a Fermi liquid. In particular, a recent system of interest is given by two-dimensional Bose-Fermi mixtures with both Bose-Fermi and Bose-Bose repulsive interactions. In the present work, a Quantum Monte Carlo study is conducted, for a fixed value of boson concentration, at zero-temperature from the weak to the strong Bose-Fermi coupling limit. Variational Monte Carlo and Fixed-Node Diffusion Monte Carlo are applied using an optimized Jastrow-Slater wavefunction, extending previous methodology developed for the three-dimensional case. The results are then compared with perturbative predictions, showing very good agreement in the weak coupling region. Variational Monte Carlo agrees with the analytic predictions only for extremely weak coupling, while Diffusion Monte Carlo proves necessary to recover good agreement over the whole perturbative regime. For stronger couplings, our simulations indicate the tendency of the mixture to form bosonic clusters. This finding would definitively deserve further investigation, which is postponed to future works.

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Duchon, Eric Nicholas. « Quantum Phase Transitions in the Bose Hubbard Model and in a Bose-Fermi Mixture ». The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386002245.

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Konishi, Hideki. « Collisional stability of localized metastable ytterbium atoms immersed in a Fermi sea of lithium ». 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225386.

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Wendland, David. « The equation of state of the Hydrogen-Helium mixture with application to the Sun ». Thesis, Lyon, École normale supérieure, 2015. http://www.theses.fr/2015ENSL1029/document.

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L’étude des propriétés d’équilibre d’un système Coulombien quantique à plusieurs composantes présente un intérêt théorique fondamental, au-delà de ses nombreuses applications. Le mélange hydrogène-hélium est omniprésent dans la nébuleuse interstellaire ou les planètes géantes, et c’est aussi le constituant majoritaire du Soleil, où les interactions entre électrons et noyaux sont purement électrostatiques en première approximation.Ce travail est dévolu à l’équation d’état de ce mélange vu comme un plasma quantique constitué de protons, de noyaux d’Hélium et d’électrons. Dans ce cadre, nous développons des méthodes numériques pour estimer des intégrales de chemin représentant des ingrédients essentiels. En outre, nous construisons une nouvelle version de la diagrammatique à la Mayer resommée bien adaptée à nos objectifs.Tout d’abord, nous améliorons le double développement basse température et basse densité, dit SLT, pour l’hydrogène pur, grâce à de meilleures estimations des termes à trois corps, les résultats étant par ailleurs comparés à la fameuse équation d’état OPAL. Les densités plus élevées sont atteintes de manière non-perturbative, en utilisant des fonctions de partition d’entités recombinées suffisamment précises. Ainsi l’ionisation par pression est décrite sur une base théorique robuste. Nous étudions également d’autres quantités d’équilibre, comme l’énergie interne et la vitesse du son. Dans la dernière partie, nous calculons l’équation d’état du mélange hydrogène-hélium en incluant les effets d’écran associés aux ions He+, ainsi que des corrections à la Debye déterminées de manière auto-cohérente. Nos résultats nous permettent de comprendre le contenu physique d’approches ad-hoc et de déterminer leurs régimes de validité. Nous obtenons aussi une description plus fiable du mélange, qui devrait être précise le long de l'adiabate du Soleil
The study of the thermodynamic properties of a multi-component quantum Coulomb system is of fundamental theoretical interest and has, beyond that, a wide range of applications. The Hydrogen-Helium mixture can be found in the interstellar nebulae and giant planets, however the most prominent example is the Sun. Here the interaction between the electrons and the nuclei is almost purely electrostatic.In this work we study the equation of state of the Hydrogen-Helium mixture starting from first principles, meaning the fundamental Coulomb interaction of its constituting particles. In this context we develop numerical methods to study the few-particle clusters appearing in the theory by using the path integral language. To capture the effects of the long-range Coulomb interaction between the fundamental particles, we construct a new version of Mayer-diagrammatic, which is appropriate for our purposes. In a first step, we ameliorate the scaled-low-temperature (SLT) equation of state, valid in the limit of low density and low temperature, by taking three-body terms into account and we compare the predictions to the well-established OPAL equation of state. Higher densities are accessed by direct inversion of the density equations and by the use of cluster functions that include screening effects. These cluster functions put the influence of screening on the ionization, unto now treated ad-hoc, on a theoretically well-grounded basis. We also inspect other equilibrium quantities such as the speed of sound and the inner energy. In the last part we calculate the equation of state of the Hydrogen-Helium mixture including the charged He+ ions in the screening process. Our work gives insights in the physical content of previous phenomenological descriptions and helps to better determine their range of validity. The equation of state derived in this thesis is expected to be very precise as well as reliable for conditions found in the Sun

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Laurent, Sébastien. « Dynamics and stability of a Bose-Fermi mixture : counterflow of superfluids and inelastic decay in a strongly interacting gas ». Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEE023/document.

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La compréhension des effets des interactions dans un ensemble de particules quantiques représente un enjeu majeur de la physique moderne. Les atomes ultra-froids sont rapidement devenus un outil incomparable pour étudier ces systèmes quantiques fortement corrélés. Dans cette thèse, nous présentons plusieurs travaux portant sur les propriétés d’un mélange de superfluides de Bose et de Fermi créé à l’aide de vapeurs ultra-froides de ⁷Li et de ⁶Li. Nous étudions tout d'abord les propriétés hydrodynamiques du mélange en créant un contre-courant entre les superfluides. L'écoulement est dissipatif uniquement au dessus d'une vitesse critique que nous mesurons dans le crossover BEC-BCS. Une simulation numérique d’un contre-courant de deux condensats permet de mieux comprendre les mécanismes sous-jacents mis en jeu dans la dynamique. En particulier, l'étude numérique fournit des preuves supplémentaires que l'origine de la dissipation dans nos expériences est liée à l'émission d'excitation élémentaires dans chaque superfluide. Finalement, nous nous intéressons aux pertes inélastiques par recombinaison à trois corps qui peuvent limiter la stabilité de nos nuages. Ces pertes sont intimement liées aux corrélations à courte distance présentes dans le système et sont ainsi connectées aux propriétés universelles du gaz quantique. Cela se manifeste notamment par l’apparition de dépendances en densité ou en température inusuelles du taux de perte lorsque le système devient fortement corrélé. Nous démontrons cet effet dans deux exemples où les interactions sont résonantes, le cas du gaz de Bose unitaire et celui de notre mélange de superfluides Bose-Fermi. Plus généralement, nos travaux montrent que ces pertes inélastiques peuvent être utilisées pour sonder les corrélations quantiques dans un système en fortes interactions
Understanding the effect of interactions in quantum many-body systems presents some of the most compelling challenges in modern physics. Ultracold atoms have emerged as a versatile platform to engineer and investigate these strongly correlated systems. In this thesis, we study the properties of a mixture of Bose and Fermi superfluids with tunable interactions produced using ultracold vapors of ⁷Li and ⁶Li. We first study the hydrodynamic properties of the mixture by creating a counterflow between the superfluids. The relative motion only exhibit dissipation above a critical velocity that we measure in the BEC-BCS crossover. A numerical simulation of counterflowing condensates allows for a better understanding of the underlying mechanisms at play in the dynamics. In particular, this numerical study provides additional evidence that the onset of friction in our experiment is due to the simultaneous generation of elementary excitations in both superfluids. Finally, we consider the inelastic losses that occur via three-body recombination in our cold gases. This few-body process is intimately related to short-distance correlations and is thereby connected to the universal properties of the many-body system. This manifests as the apparition of an unusual dependence on density or temperature in the loss rate when increasing the interactions. We demonstrate this effect in two examples where interactions are resonant: the case of a dilute unitary Bose gas and the one of impurities weakly coupled to a unitary Fermi gas. More generally, our work shows that inelastic losses can be used to probe quantum correlations in a many-body system

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PANTALEI, CLAUDIA. « Single-particle dynamics of helium mixtures and 4He in nanometric confinement ». Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/473.

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Scopo di questa tesi e' lo studio, tramite Deep Inelastic Neutron Scattering, della dinamica microscopica di due differenti sistemi di elio, a bassa temperatura (circa 2 K): una miscela isotopica (nella fase fluida e vicino al punto di melting) e 4He in in confinamento nanometrico. L'interesse per l'elio, gia' dai primi decenni del `900, nasce dalla sua unica proprieta': e' l'unico elemento in natura a non avere una fase solida allo zero assoluto. A basse temperature, quindi, presenta effetti quantistici, normalmente trascurabili in altri sistemi fisici, che nelle stesse condizioni solidificano. l'elio e' quindi l'unico banco di prova per i modelli teorici quantistici, in particolare per lo studio di bosoni e fermioni interagenti. In questo contesto, molti esperimenti sono stati effettuati sull'elio, sia nella fase liquida che solida. Misure su 3He e 4He hanno mostrato che l'energia cinetica dei liquidi puri dipende dalla densita' del sistema, crescendo con una diminuzione del volume molare. D'altra parte, la dinamica microscopica delle miscele mostra un differente comportamento rispetto al 3He e 4He puri: l'energia cinetica media dell'isotopo piu' leggero, a volumi molari maggiori di 25cm3/mole, sembra essere indipendente dal volume molare e dalla concentrazione. Questo andamento potrebbe essere spiegato da effetti quantistici, come gli effetti di scambio. Nella prima parte del presente lavoro si e' investigata la dinamica delle miscele per volumi molari tra 22cm3/mole e 25cm3/mole, e gli esperimenti compiuti hanno mostrato che in questo range di volumi molari l'energia cinetica media degli atomi di 3He risulta dipendente dal volume molare, aumentando fino ad avere un valore corrispondente a quello del 3He puro. Recentemente sono state compiute anche misure per studiare l'influenza di un confinamento sull'elio. Esperimenti su 4He, adsorbito in superfici piane o substrati porosi, hanno rivelato un elevato aumento nel valore dell'energia cinetica. Questo comportamento e' stato attribuito alla localizzazione degli atomi di He dovuta al potenziale di interazione He-substrato, che influenza fortemente i primi due o tre layers. Questi tipi di effetti possono essere studiati confinando 4He in pori cilindrici con differenti diametri dei pori. Scopo della seconda parte di questa tesi e' stata appunto quella di determinare l'energia cinetica media degli atomi di 4He adsorbiti in sistemi nanoporosi a geometria cilindrica (Xerogel) con due diametri medi dei pori, di 24ºA 160ºA, per valutare la dipendenza della dinamica a singola particella con la dimensione dei pori e con il tipo di geometria. Le misure sono state effettuate a T=2.5K, a pressione di vapor saturo e con un riempimento dei pori del 95%. L'esperimento ha mostrato che l'energia cinetica del 4He nei pori e' maggiore rispetto a quella del 4He liquido nelle stesse condizioni. I risultati sono stati interpretati tramite un modello teorico, secondo il quale gli atomi si posizionano in anelli concentrici, stratificando layer per layer, e con un'energia cinetica dipendente dal rapporto tra il diametro del poro e quello dell'atomo di elio.
The aim of this thesis work is the study, by means of Deep Inelastic Neutron Scatter- ing, of the microscopic dynamics of two different helium systems at low temperature (T=2K): an isotopic helium mixture (in the fluid phase and near the melting point) and a system of 4He in nanometric confinement. The interest in the helium, from the first decades of 1900, is due to its unique features: it is the only element in nature that doesn't have a solid phase at absolute zero. Thus, at low temperatures it presents quantum effects, usually negligible in other physical systems that in this condition crystallise. The helium is thus the unique test-bed for theoretical quantum models, in particular for studying the interacting boson (4He) and fermion (3He) systems. Moreover, if in 4He are added some atoms of 3He it is possible to derive important information about the interplay of these two statistics. In this context, several experiments on liquid and solid helium have been performed. Measurements on pure 3He and 4He have shown that the mean kinetic energy of pure liquids depends on the density of the system and increases decreasing the molar volume. On the other hand, the microscopic dynamics of helium mixtures reveals quite a different picture with respect to pure 3He and 4He: the mean kinetic energy of the light isotope, above a molar volume of 25cm3/mole, shows a remarkable independence from molar volume and concentration. This behaviour could be explained by quantum effects, such as exchange effects. The first part of the present work deals with the experiments performed to investigate the dynamics of the mixtures from 22cm3/mole to 25cm3/mole and shows how, at these low molar volumes, the mean kinetic energy of 3He starts again to be strongly dependent on the molar volume, increasing until reaching, at 22.7cm3/mole, the corresponding value of pure helium. Recent measurements have been also performed to investigate the influence of confinement on helium. Experiments on 4He, adsorbed in flat surface or slit geometry porous substrates, have shown a large increase in helium mean kinetic energy. This has been attributed to the strong localisation effects induced by the helium-substrate interaction potential, which mainly influence the firsts two or three adsorbed layers. Such effects can be also investigated by confining 4He atoms in cylindrical pore geometries and by studying their dynamics as function of pore size. Aim of the second part of the thesis has been the determination of the single particle mean kinetic energy of 4He adsorbed in cylindrical silica nanopores (Xerogel) having two different pore diameters, namely, 24 ºAand 160 ºA, and to evaluate the dependence of single- particle dynamics on pore sizes, layer coverage, and confining system geometry. The measurements have been performed at a temperature of T=2.5K, saturated vapour pressure, and 95% volume filling. Significant changes in the values of the single particle mean kinetic energy are found: they are remarkably higher than the value of normal liquid 4He at the same conditions. The results are interpreted in terms of a model in which 4He atoms are arranged in concentric annuli along the cylindrical pore axis, growing layer-by-layer and with the mean kinetic energy mainly dependent on the ratio between the atomic diameter and the pore diameter.

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Livres sur le sujet "Quantum mixture"

Yudaev, Vasiliy. Hydraulics. ru : INFRA-M Academic Publishing LLC., 2021. http://dx.doi.org/10.12737/996354.

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The textbook corresponds to the general education programs of the general courses "Hydraulics" and "Fluid Mechanics". The basic physical properties of liquids, gases, and their mixtures, including the quantum nature of viscosity in a liquid, are described; the laws of hydrostatics, their observation in natural phenomena, and their application in engineering are described. The fundamentals of the kinematics and dynamics of an incompressible fluid are given; original examples of the application of the Bernoulli equation are given. The modes of fluid motion are supplemented by the features of the transient flow mode at high local resistances. The basics of flow similarity are shown. Laminar and turbulent modes of motion in pipes are described, and the classification of flows from a creeping current to four types of hypersonic flow around the body is given. The coefficients of nonuniformity of momentum and kinetic energy for several flows of Newtonian and non-Newtonian fluids are calculated. Examples of solving problems of transient flows by hydraulic methods are given. Local hydraulic resistances, their use in measuring equipment and industry, hydraulic shock, polytropic flow of gas in the pipe and its outflow from the tank are considered. The characteristics of different types of pumps, their advantages and disadvantages, and ways of adjustment are described. A brief biography of the scientists mentioned in the textbook is given, and their contribution to the development of the theory of hydroaeromechanics is shown. The four appendices can be used as a reference to the main text, as well as a subject index. Meets the requirements of the federal state educational standards of higher education of the latest generation. For students of higher educational institutions who study full-time, part-time, evening, distance learning forms of technological and mechanical specialties belonging to the group "Food Technology".

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Schroeder, Daniel V. An Introduction to Thermal Physics. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192895547.001.0001.

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Thermal physics deals with collections of large numbers of particles—typically 10²³ or so. Examples include the air in a balloon, the water in a lake, the electrons in a chunk of metal, and the photons given off by the sun. We can't possibly follow every detail of the motions of so many particles. So in thermal physics we assume that these motions are random, and we use the laws of probability to predict how the material as a whole ought to behave. Alternatively, we can measure the bulk properties of a material, and from these infer something about the particles it is made of. This book will give you a working understanding of thermal physics, assuming that you have already studied introductory physics and calculus. You will learn to apply the general laws of energy and entropy to engines, refrigerators, chemical reactions, phase transformations, and mixtures. You will also learn to use basic quantum physics and powerful statistical methods to predict in detail how temperature affects molecular speeds, vibrations of solids, electrical and magnetic behaviors, emission of light, and exotic low-temperature phenomena. The problems and worked examples explore applications not just within physics but also to engineering, chemistry, biology, geology, atmospheric science, astrophysics, cosmology, and everyday life.

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Chapitres de livres sur le sujet "Quantum mixture"

Pu, H., W. Zhang et P. Meystre. « Phonon excitations and stability of a Bose-Fermi mixture quantum gas ». Dans Coherence and Quantum Optics VIII, 589–90. Boston, MA : Springer US, 2003. http://dx.doi.org/10.1007/978-1-4419-8907-9_182.

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Hallock, Robert B. « NMR Measurements of 3 He in 3 He- 4 He Mixture Films ». Dans Excitations in Two-Dimensional and Three-Dimensional Quantum Fluids, 269–79. Boston, MA : Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-5937-1_26.

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Meystre, Pierre, et Murray Sargent. « Mixtures and the Density Operator ». Dans Elements of Quantum Optics, 101–28. Berlin, Heidelberg : Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-662-11654-8_4.

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Meystre, Pierre, et Murray Sargent. « Mixtures and the Density Operator ». Dans Elements of Quantum Optics, 101–28. Berlin, Heidelberg : Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-662-07007-9_4.

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Meystre, Pierre, et Murray Sargent. « Mixtures and the Density Operator ». Dans Elements of Quantum Optics, 93–116. Berlin, Heidelberg : Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-74211-1_4.

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Meystre, Pierre, et Murray Sargent. « Mixtures and the Density Operator ». Dans Elements of Quantum Optics, 81–102. Berlin, Heidelberg : Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-662-03877-2_4.

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Bowley, R. M. « Bulk Properties of 3He-4He Mixtures ». Dans Excitations in Two-Dimensional and Three-Dimensional Quantum Fluids, 183–94. Boston, MA : Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-5937-1_18.

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Will, Sebastian. « Interacting Mixtures of Bosons and Fermions in Optical Lattice Potentials ». Dans From Atom Optics to Quantum Simulation, 193–207. Berlin, Heidelberg : Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-33633-1_8.

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van Beelen, H. « Thermal Counterflow in Superfluid 3He-4He Mixtures ». Dans Excitations in Two-Dimensional and Three-Dimensional Quantum Fluids, 221–29. Boston, MA : Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-5937-1_21.

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Balibar, S., et H. Meyer. « Discussion on Bulk 3He and 3He/4He Mixtures ». Dans Excitations in Two-Dimensional and Three-Dimensional Quantum Fluids, 251–55. Boston, MA : Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-5937-1_24.

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Actes de conférences sur le sujet "Quantum mixture"

Modugno, G., G. Roati, F. Ferlaino et M. Inguscio. « Experiments with a quantum degenerate Fermi-Bose mixture ». Dans 2003 European Quantum Electronics Conference. EQEC 2003 (IEEE Cat No.03TH8665). IEEE, 2003. http://dx.doi.org/10.1109/eqec.2003.1314146.

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Webb, Kevin J., et Alon Ludwig. « Lossless Negative Dielectric Constant Optical Material from a Semiconductor Quantum Dot Mixture ». Dans International Quantum Electronics Conference. Washington, D.C. : OSA, 2009. http://dx.doi.org/10.1364/iqec.2009.itul7.

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John, Shincy, Nicolas Spethmann, Claudia Weber, Tatjana Weikum, Artur Widera et Dieter Meschede. « Interspecies interaction in a strongly imbalanced Bose-Bose mixture ». Dans 11th European Quantum Electronics Conference (CLEO/EQEC). IEEE, 2009. http://dx.doi.org/10.1109/cleoe-eqec.2009.5192914.

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Korkinof, Dimitrios, et Yiannis Demiris. « Online quantum mixture regression for trajectory learning by demonstration ». Dans 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2013). IEEE, 2013. http://dx.doi.org/10.1109/iros.2013.6696814.

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Higley, R. H., D. T. Sprague et R. B. Hallock. « Structure in the magnetization of thin 3He-4He mixture films ». Dans Symposium on quantum fluids and solids−1989. AIP, 1989. http://dx.doi.org/10.1063/1.38780.

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Carmi, Yoash, Stephen Lipson et Emil Polturak. « Roughening and wetting transitions in dilute 3He-4He mixture crystals ». Dans Symposium on quantum fluids and solids−1989. AIP, 1989. http://dx.doi.org/10.1063/1.38797.

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Spiegelhalder, F., A. Trenkwalder, D. Naik, E. Wille, G. Hendl, F. Schreck et R. Grimm. « All-optical production of a doubly degenerate Fermi-Fermi mixture ». Dans 11th European Quantum Electronics Conference (CLEO/EQEC). IEEE, 2009. http://dx.doi.org/10.1109/cleoe-eqec.2009.5192440.

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Shadbolt, Peter, Maria Rodas Verde, Alberto Peruzzo, Alberto Politi, Anthony Laing, Mirko Lobino, Jonathan Matthews, Mark G. Thompson et Jeremy L. O'Brien. « A Reconfigurable Photonic Chip for Generating, Manipulating and Measuring Entanglement and Mixture ». Dans Quantum Electronics and Laser Science Conference. Washington, D.C. : OSA, 2012. http://dx.doi.org/10.1364/qels.2012.qf2f.1.

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Lim, Sun Hee, Felix Bestwater, Philippe Buchy, Sek Mardy et Alexey Dan Chin Yu. « Quantum-dot-based quantitative identification of pathogens in complex mixture ». Dans BiOS, sous la direction de Marek Osinski, Wolfgang J. Parak, Thomas M. Jovin et Kenji Yamamoto. SPIE, 2010. http://dx.doi.org/10.1117/12.851050.

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Zhao, Liancheng, Ruiyi Zhu, Xuelong Liu, Zhenxu Wang, Qi L. Wang et Zuguang Ma. « Two-step excitation of He/K mixture for producing coherent XUV radiation ». Dans 1992 Shanghai International Symposium on Quantum Optics, sous la direction de Yuzhu Wang, Yiqiu Wang et Zugeng Wang. SPIE, 1992. http://dx.doi.org/10.1117/12.130479.

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Rapports d'organisations sur le sujet "Quantum mixture"

Jin, Deborah. Exploring Quantum Degenerate Bose-Fermi Mixtures Toward Cooper Pairing of Fermionic Atoms. Office of Scientific and Technical Information (OSTI), avril 2011. http://dx.doi.org/10.2172/1011496.

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