المؤلفون: Lecoutre, Baptiste, Guo, Yukun, Yu, Xudong, Niranjan, M., Mukhtar, Musawwadah, Volchkov, Valentin V., Aspect, Alain, Josse, Vincent

مصطلحات موضوعية: Condensed Matter - Quantum Gases

الوصف: The ability to load ultracold atoms at a well-defined energy in a disordered potential is a crucial tool to study quantum transport, and in particular Anderson localization. In this paper, we present a new method for achieving that goal by rf transfer of atoms of an atomic Bose-Einstein condensate from a disorder insensitive state to a disorder sensitive state. It is based on a bichromatic laser speckle pattern, produced by two lasers whose frequencies are chosen so that their light-shifts cancel each other in the first state and add-up in the second state. Moreover, the spontaneous scattering rate in the disorder-sensitive state is low enough to allow for long observation times of quantum transport in that state. We theoretically and experimentally study the characteristics of the resulting potential.
Comment: 14 pages, 7 figures

الوصول الحر: http://arxiv.org/abs/2208.12166Test

المؤلفون: Pelletier, Pierre, Delande, Dominique, Josse, Vincent, Aspect, Alain, Mayboroda, Svitlana, Arnold, Douglas, Filoche, Marcel

مصطلحات موضوعية: Quantum Physics

الوصف: Spectral function is a key tool for understanding the behavior of Bose-Einstein condensates of cold atoms in random potentials generated by a laser speckle. In this paper we introduce a new method for computing the spectral functions in disordered potentials. Using a combination of the Wigner-Weyl approach with the landscape theory, we build an approximation for the Wigner distributions of the eigenstates in the phase space and show its accuracy in all regimes, from the deep quantum regime to the intermediate and semiclassical. Based on this approximation, we devise a method to compute the spectral functions using only the landscape-based effective potential. The paper demonstrates the efficiency of the proposed approach for disordered potentials with various statistical properties without requiring any adjustable parameters.
Comment: 10 pages, 10 figures

الوصول الحر: http://arxiv.org/abs/2111.13155Test

المؤلفون: Signoles, Adrien, Lecoutre, Baptiste, Richard, Jérémie, Lim, Lih-King, Denechaud, Vincent, Volchkov, Valentin V., Angelopoulou, Vasiliki, Jendrzejewski, Fred, Aspect, Alain, Sanchez-Palencia, Laurent, Josse, Vincent

المصدر: New J. Phys. 21 105002 2019

مصطلحات موضوعية: Condensed Matter - Quantum Gases, Condensed Matter - Disordered Systems and Neural Networks

الوصف: We study the elastic scattering time $\tau_\mathrm{s}$ of ultracold atoms propagating in optical disordered potentials in the strong scattering regime, going beyond the recent work of J. Richard \emph{et al.} \textit{Phys. Rev. Lett.} \textbf{122} 100403 (2019). There, we identified the crossover between the weak and the strong scattering regimes by comparing direct measurements and numerical simulations to the first order Born approximation. Here we focus specifically on the strong scattering regime, where the first order Born approximation is not valid anymore and the scattering time is strongly influenced by the nature of the disorder. To interpret our observations, we connect the scattering time $\tau_\mathrm{s}$ to the profiles of the spectral functions that we estimate using higher order Born perturbation theory or self-consistent Born approximation. The comparison reveals that self-consistent methods are well suited to describe $\tau_\mathrm{s}$ for Gaussian-distributed disorder, but fails for laser speckle disorder. For the latter, we show that the peculiar profiles of the spectral functions, as measured independently in V. Volchkov \emph{et al.} \textit{Phys. Rev. Lett.} \textbf{120}, 060404 (2018), must be taken into account. Altogether our study characterizes the validity range of usual theoretical methods to predict the elastic scattering time of matter waves, which is essential for future close comparison between theory and experiments, for instance regarding the ongoing studies on Anderson localization.
Comment: 21 pages, 6 figures

الوصول الحر: http://arxiv.org/abs/1910.04148Test

المؤلفون: Richard, Jérémie, Lim, Lih-King, Denechaud, Vincent, Volchkov, Valentin V., Lecoutre, Baptiste, Mukhtar, Musawwadah, Jendrzejewski, Fred, Aspect, Alain, Signoles, Adrien, Sanchez-Palencia, Laurent, Josse, Vincent

المصدر: Phys. Rev. Lett. 122, 100403 (2019)

مصطلحات موضوعية: Condensed Matter - Quantum Gases, Condensed Matter - Disordered Systems and Neural Networks

الوصف: We report on an extensive study of the elastic scattering time $\tauS$ of matter-waves in optical disordered potentials. Using direct experimental measurements, numerical simulations and comparison with first-order Born approximation based on the knowledge of the disorder properties, we explore the behavior of $\tauS$ over more than three orders of magnitude, spanning from the weak to the strong scattering regime. We study in detail the location of the crossover and, as a main result, we reveal the strong influence of the disorder statistics, especially on the relevance of the widely used Ioffe-Regel-like criterion $k\lS\sim 1$. While it is found to be relevant for Gaussian-distributed disordered potentials, we observe significant deviations for laser speckle disorders that are commonly used with ultracold atoms. Our results are crucial for connecting experimental investigation of complex transport phenomena, such as Anderson localization, to microscopic theories.
Comment: 6+4 pages, 3+4 figures

الوصول الحر: http://arxiv.org/abs/1810.07574Test

المؤلفون: Volchkov, Valentin V., Pasek, Michael, Denechaud, Vincent, Mukhtar, Musawwadah, Aspect, Alain, Delande, Dominique, Josse, Vincent

المصدر: Phys. Rev. Lett. 120, 060404 (2018)

مصطلحات موضوعية: Condensed Matter - Quantum Gases, Condensed Matter - Disordered Systems and Neural Networks

الوصف: We report on the measurement of the spectral functions of noninteracting ultracold atoms in a three-dimensional disordered potential resulting from an optical speckle field. Varying the disorder strength by 2 orders of magnitude, we observe the crossover from the "quantum" perturbative regime of low disorder to the "classical" regime at higher disorder strength, and find an excellent agreement with numerical simulations. The method relies on the use of state-dependent disorder and the controlled transfer of atoms to create well-defined energy states. This opens new avenues for experimental investigations of three-dimensional Anderson localization.

الوصول الحر: http://arxiv.org/abs/1707.07577Test

المؤلفون: Müller, Kilian, Richard, Jérémie, Volchkov, Valentin V., Denechaud, Vincent, Bouyer, Philippe, Aspect, Alain, Josse, Vincent

المصدر: Phys. Rev. Lett. 114, 205301 (2015)

مصطلحات موضوعية: Condensed Matter - Quantum Gases, Condensed Matter - Disordered Systems and Neural Networks

الوصف: We report on the observation of suppression and revival of coherent backscattering of ultra-cold atoms launched in an optical disorder and submitted to a short dephasing pulse, as proposed in a recent paper of T. Micklitz \textit{et al.} [arXiv:1406.6915]. This observation, in a quasi-2D geometry, demonstrates a novel and general method to study weak localization by manipulating time reversal symmetry in disordered systems. In future experiments, this scheme could be extended to investigate higher order localization processes at the heart of Anderson (strong) localization.
Comment: 5 pages, 5 figures

الوصول الحر: http://arxiv.org/abs/1411.1671Test

المؤلفون: Josse, Vincent

مصطلحات موضوعية: [PHYS:PHYS:PHYS_ATOM-PH] Physics/Physics/Atomic Physics, Fluctuations quantiques, bascule de polarisation, réduction du bruit de polarisation, corrélations quantiques, atomes froids

الوصف: Nous avons étudié les fluctuations quantiques du champ électromagnétique ayant interagi avec un nuage d'atomes froids placé à l'intérieur d'une cavité optique. Proche de résonance, le milieu atomique se comporte comme un milieu non-linéaire en raison de la saturation de la transition optique. Lorsque le faisceau incident est polarisé linéairement, cette saturation se traduit par un effet de type Kerr sur le champ moyen et de type Kerr-croisé sur le mode vide orthogonal. Ces effets non-linéaires modifient les fluctuations de ces modes du champs. Nous avons alors pu observer la réduction du bruit sous la limite quantique standard sur ces deux modes. Nous avons interprété la réduction de bruit sur le mode vide orthogonal en terme de réduction du bruit de polarisation du faisceau. Les fluctuations de polarisation ont été caractérisées par la mesure des fluctuations des paramètres de Stokes. Par ailleurs, nous avons étudié les corrélations quantiques produites par le système. Ces corrélations ont été estimées à l'aide d'un critère de nonséparabilité, valable pour les variables continues. Nous avons alors montré que les modes polarisés à °45° (par rapport au champ moyen) sont intriqués en quadrature. Cette intrication a ensuite été utilisée pour produire deux faisceaux intriqués en polarisation.

الإتاحة: http://tel.archives-ouvertes.fr/tel-00004876Test
http://tel.archives-ouvertes.fr/docs/00/04/62/06/PDF/tel-00004876.pdfTest

المؤلفون: Vest, B., Bernard, Fabienne, de Rossi, Sébastien, Josse, Vincent, Boffety, Matthieu, Villemejane, Julien, Moyon, Marine, Riopel, Martin, Potvin, Patrice

المساهمون: Laboratoire Charles Fabry / Nanophotonique, Laboratoire Charles Fabry (LCF), Institut d'Optique Graduate School (IOGS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut d'Optique Graduate School (IOGS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut d'Optique Graduate School (IOGS), Laboratoire Charles Fabry / Optique XUV, Laboratoire Charles Fabry / Gaz Quantiques, Laboratoire Charles Fabry / Imagerie et Information, Institut Villebon – Georges Charpak, Université Paris-Saclay, Université du Québec à Montréal = University of Québec in Montréal (UQAM), Université Paris-Saclay, Research Action Chair on Educational Innovation, Chaire de recherche-action sur l'innovation pédagogique de l'Université Paris-Saclay

المصدر: ESERA 2021 : Fostering scientific citizenship in an uncertain world, Proceedings of ESERA 2021 ; https://hal-iogs.archives-ouvertes.fr/hal-04006418Test ; ESERA 2021 : Fostering scientific citizenship in an uncertain world, Proceedings of ESERA 2021, Part 17 (Chap 5), pp.1296-1304, 2021, 978-972-8952-82-2

مصطلحات موضوعية: Evidence-Based Approaches Higher Education STEM Education, Evidence-Based Approaches, Higher Education, STEM Education, [SHS.EDU]Humanities and Social Sciences/Education

الوصف: International audience ; Evidence-based approaches in teaching and learning provide strategies to empower student learning and long-term retention of knowledge. Such strategies can be implemented at the course level by a single teacher, which then happens at a smaller scale. However, a more powerful approach consists in a coherent integration of neuroeducational principles in the entire structure of a term, involving several courses over several months. This represents an educational change at a higher scale, however facing several risks in its in-practice implementation, such as faculty reluctance and resource insufficiency. We report here on the design of a whole academic term for optical engineering students in dual education at the Bachelor level. It was devised in order to maximize retention effects through a coherent and coordinated use of constructive alignment in course design, active learning activities, metacognition course, and spaced learning. The design process is encompassed within a SoTL (Scholarship of Teaching and Learning) methodology cycle. It involved a total of 12 faculty members, led by a core group of six, trained by educational advisors in neurodidactics, and tasked with the global design, planning and management of the project. At the pre-roll out stage, this work delivered collectively elaborated timetables, syllabus, balanced student workloads, and plans for team teaching and shared educational tasks.

العلاقة: hal-04006418; https://hal-iogs.archives-ouvertes.fr/hal-04006418Test; https://hal-iogs.archives-ouvertes.fr/hal-04006418/documentTest; https://hal-iogs.archives-ouvertes.fr/hal-04006418/file/From_scratch_hatch.pdfTest

الإتاحة: https://hal-iogs.archives-ouvertes.fr/hal-04006418Test
https://hal-iogs.archives-ouvertes.fr/hal-04006418/documentTest
https://hal-iogs.archives-ouvertes.fr/hal-04006418/file/From_scratch_hatch.pdfTest

المؤلفون: Jendrzejewski, Fred, Müller, Kilian, Richard, Jérémie, Date, Aditya, Plisson, Thomas, Bouyer, Philippe, Aspect, Alain, Josse, Vincent

المصدر: Physical Review Letters 109 (2012) 195302

مصطلحات موضوعية: Physics - Atomic Physics, Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Quantum Gases

الوصف: We report on the direct observation of coherent backscattering (CBS) of ultracold atoms, in a quasi-two-dimensional configuration. Launching atoms with a well-defined momentum in a laser speckle disordered potential, we follow the progressive build up of the momentum scattering pattern, consisting of a ring associated with multiple elastic scattering, and the CBS peak in the backward direction. Monitoring the depletion of the initial momentum component and the formation of the angular ring profile allows us to determine microscopic transport quantities. The time resolved evolution of the CBS peak is studied and is found a fair agreement with predictions, at long times as well as at short times. The observation of CBS can be considered a direct signature of coherence in quantum transport of particles in disordered media. It is responsible for the so called weak localization phenomenon, which is the precursor of Anderson localization.
Comment: 5 pages, 4 figures

الوصول الحر: http://arxiv.org/abs/1207.4775Test

المؤلفون: Jendrzejewski, Fred, Bernard, Alain, Mueller, Killian, Cheinet, Patrick, Josse, Vincent, Piraud, Marie, Pezzé, Luca, Sanchez-Palencia, Laurent, Aspect, Alain, Bouyer, Philippe

المصدر: Nature Physics 8 (2012) 398-403

مصطلحات موضوعية: Condensed Matter - Quantum Gases, Condensed Matter - Other Condensed Matter

الوصف: We report a study of three-dimensional (3D) localization of ultracold atoms suspended against gravity, and released in a 3D optical disordered potential with short correlation lengths in all directions. We observe density profiles composed of a steady localized part and a diffusive part. Our observations are compatible with the self-consistent theory of Anderson localization, taking into account the specific features of the experiment, and in particular the broad energy distribution of the atoms placed in the disordered potential. The localization we observe cannot be interpreted as trapping of particles with energy below the classical percolation threshold.
Comment: published in Nature Physics; The present version is the initial manuscript (unchanged compared to version 1); The published version is available online at http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys2256.htmlTest

الوصول الحر: http://arxiv.org/abs/1108.0137Test