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DTSTART;TZID=Europe/Paris:20241203T140000
DTEND;TZID=Europe/Paris:20241203T153000
DTSTAMP:20260413T182631
CREATED:20241202T083342Z
LAST-MODIFIED:20241202T091845Z
UID:11113-1733234400-1733239800@fermi.univ-tlse3.fr
SUMMARY:Caractérisation des paramagnétiques quantiques 3D à l’aide des contraintes de Lieb-Schultz-Mattis. - (Chunxiao Liu / LPT / Seminar). - 3/12/2024\, 14H
DESCRIPTION:Séminaire LPT \nChunxiao Liu (UC Berkeley) \nSeminar LPT\, 3/12/2024\, 14H\, 3R4\, salle de conférence \nSummary\nQuantum paramagnets represent intriguing quantum phases that evade ordering even at absolute zero temperature. While detecting their presence is relatively straightforward\, unraveling their fundamental nature can be a challenging task. In this talk\, I will present our recent work [1] on Lieb-Schultz-Mattis (LSM) constraints which prohibit certain quantum paramagnets from being a « trivial » one. I will illustrate the use of these results through two examples : (1) the prediction of a Dirac spin liquid in the triangular lattice compound NaYbO2\, and (2) the characterization of U(1) quantum spin liquids in a pyrochlore S=1/2 antiferromagnet. I will highlight the topological response theory underlying the LSM constraints that we developed\, containing information about symmetry\, excitations\, and lattice defects\, applicable to all 3D quantum paramagnets. \n[1] Liu & Ye\, arXiv:2410.03607
URL:https://fermi.univ-tlse3.fr/event/tba-chunxiao-liu-lpt-seminar-3-12-2024-14h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241210T140000
DTEND;TZID=Europe/Paris:20241210T153000
DTSTAMP:20260413T182631
CREATED:20241209T073022Z
LAST-MODIFIED:20241209T083741Z
UID:11186-1733839200-1733844600@fermi.univ-tlse3.fr
SUMMARY:Rôle des corrélations de l’espace de Fock dans la localisation à plusieurs corps / Simulation quantique sur ordinateurs quantiques bruyants (NISQ). – (Thibault Scoquart  / LPT / Seminar). – 10/12/2024\, 14H
DESCRIPTION:Séminaire LPT \nThibault Scoquart (Institut de technologie de Karlsruhe) \nSeminar LPT\, 10/12/2024\, 14H\, 3R4\, salle de conférence \nSummary : \nIn this seminar\, I will discuss two (more or less) unrelated projects that I worked on during my postdoc at KIT.\nIn a first part\, I will present our conclusions regarding the role of correlations of Fock-space matrix elements in ergodicity-to-Many-Body Localization (MBL) transitions [1]. To study this\, we introduce five different disordered spin models and describe analytically and numerically the scaling of their finite-size critical disorder Wc(n) with the system size n. The MBL transition in these models can be seen as the Anderson localization problem for a fictitious particle hopping over their hypercube Fock space structure. The models are built such that they have the same distributions of diagonal (energy) and off-diagonal (hopping) Fock-space matrix elements but very different correlations. One of these models is a typical disordered 1D spin chain\, paradigmatic for the study of MBL\, and another is the quantum random energy model (QREM) with no Fock-space correlations at all\, making it analytically more tractable. The three other models bridge the gap between these two extremes. A cross-comparison of Wc(n) for all five models demonstrates to which extent the scaling of the MBL transition is governed by a combined effect of Fock-space correlations of diagonal and off-diagonal matrix elements.\nIn a second part of the talk\, I will give an overview of our work on digital quantum simulations performed on IBM superconducting quantum computers\, one of the main current im- plementations of Noisy Intermediate-Scale Quantum computers (NISQ). The focus will be on our work about noise characterization\, noise tailoring and error mitigation via quantum circuit sampling on such devices\, using short-scale simulations of BCS dynamics as a benchmark [2\, 3]. I will also discuss some perspectives on the quantum simulation of quenched thermalizing dynamics on NISQ [4]. \n[1] T. Scoquart\, I. Gornyi and A. Mirlin\, Role of Fock-space correlations in many-body localization\, Physical Review B 109\, 214203\, (2024) \n[2] H. Perrin\, T. Scoquart\, A. Shnirman\, J. Schmalian\, and K. Snizhko\, Mitigating crosstalk errors by randomized compiling : Simulation of the BCS model on a superconducting quantum computer\, Phys. Rev. Research 6\, 013142 (2024) \n[3] T. Scoquart\, H. Perrin and K. Snizkho\, Noise-tailoring for error mitigation on a digital quantum computer (Soon to appear on arXiv) \n[4] H. Perrin\, T. Scoquart\, A. I. Pavlov\, N. V. Gnezdilov\, Dynamic thermalization on noisy quantum hardware\, arXiv:2407.04770
URL:https://fermi.univ-tlse3.fr/event/tba-thibault-scoquart-lpt-seminar-10-12-2024-14h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241212T100000
DTEND;TZID=Europe/Paris:20241212T113000
DTSTAMP:20260413T182631
CREATED:20241212T064806Z
LAST-MODIFIED:20241212T100959Z
UID:11232-1733997600-1734003000@fermi.univ-tlse3.fr
SUMMARY:Physique quantique à plusieurs corps avec des fermions dans une boîte optique. - (Nir Navon/ LPT / Seminar). - 12/12/2024\, 10H
DESCRIPTION:Séminaire LPT \nNir Navon (Université Yale) \nSeminar LPT\, 12/12/2024\, 10H\, 3R4\, salle de conférence \nSummary\nFor the past two decades harmonically trapped ultracold atomic gases have been used with great success to study fundamental many-body physics in flexible experimental settings. However\, the resulting gas density inhomogeneity in those traps makes it challenging to study paradigmatic uniform-system physics (such as critical behavior near phase transitions) or complex quantum dynamics. \nThe realization of homogeneous quantum gases trapped in optical boxes has marked a milestone in the quantum simulation program with ultracold atoms [1]. These textbook systems have proved to be a powerful playground by simplifying the interpretation of experimental measurements\, by making more direct connections to theories of the many-body problem that generally rely on the translational symmetry of the system\, and by altogether enabling previously inaccessible experiments. \nIn this talk\, I will present some of our recent studies of many-body physics with ultracold fermions trapped in a box of light [2-6]. This platform is particularly suitable to study problems of Fermi-system stability\, of which I will discuss two cases : the spin-1/2 Fermi gas with repulsive contact interactions [2]\, and the three-component Fermi gas with spin-population imbalance [3]. Both studies lead to surprising results\, highlighting how spatial homogeneity not only simplifies the connection between experiments and theory\, but can also unveil unexpected outcomes. I will also present other recent works\, including the first observation of the fermionic Joule-Thomson effect [4]\, the strongly driven Fermi polaron [5]\, and the emergence of sound in a Fermi gas with tunable interactions [6]. \nReferences :\n[1] N. Navon\, R.P. Smith\, Z. Hadzibabic\, Nature Phys. 17\, 1334 (2021) \n[2] Y. Ji et al.\, Phys. Lev. Lett 129\, 203402 (2022) \n[3] G.L. Schumacher et al.\, arXiv:2301.02237 \n[4] Y. Ji et al.\, Phys. Lev. Lett 132\, 153402 (2024) \n[5] F.J. Vivanco \, arXiv:2308.05746 \n[6] S. Huang\, arXiv:2407.13769
URL:https://fermi.univ-tlse3.fr/event/physique-quantique-a-plusieurs-corps-avec-des-fermions-dans-une-boite-optique-nir-navon-lpt-seminar-12-12-2024-10h-2/
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241212T150000
DTEND;TZID=Europe/Paris:20241212T180000
DTSTAMP:20260413T182631
CREATED:20241212T051335Z
LAST-MODIFIED:20241212T101016Z
UID:11220-1734015600-1734026400@fermi.univ-tlse3.fr
SUMMARY:Onde de densité dans un gaz de fermions : phonons et plasmons\, du régime hydrodynamique au régime non-collisionnel. - (Thomas Repplinger / LPT / Thèse). - 12/12/2024\, 15H
DESCRIPTION:Soutenance de thèse \nThomas Repplinger\, LPT\, Salle de conférence\, Bat. 3R4 \nRésumé: \nLa théorie de Landau des liquides de Fermi est un cadre de travail qui simplifie la description de la dynamique de certains systèmes de fermions en s’appuyant sur la résolution d’une équation de Boltzmann. Cette théorie décrit le comportement à basse température de la plupart des métaux\, ainsi que de l’hélium 3. L’un de ses plus grands succès a été la prédiction du son zéro\, un son non-collisionnel\, qui a ensuite été mesuré expérimentalement dans l’hélium 3. Malgré de nombreux efforts\, un désaccord quantitatif persiste entre la théorie et les expériences. En cause\, l’interaction entre quasiparticules et la probabilité de collisions\, lesquelles ne peuvent pas être calculées à partir d’une théorie microscopique. \nAvec l’avènement des gaz ultrafroids d’atomes fermioniques\, nous avons désormais la possibilité de tester quantitativement la théorie de Landau\, notamment en ce qui concerne les propriétés de transport. C’est dans ce cadre que s’inscrit ma thèse. Je commencerai par introduire les principes fondamentaux de cette théorie. Nous examinerons ensuite son application aux gaz de fermions homogènes\, en particulier dans le contexte de l’expérience menée par Nir Navon (Yale). Cela nous permettra de calculer exactement leurs propriétés de transport (viscosité de cisaillement et conductivité thermique) à toutes les températures\, résultats connue mais oublié dans le contexte des atomes froids\, ainsi que la dispersion du son hydrodynamique à basse température. Pour terminer\, nous comparerons la réponse linéaire calculée dans le cadre des liquides de Fermi avec les mesures effectuées à Yale. \n\n \n \n 
URL:https://fermi.univ-tlse3.fr/event/onde-de-densite-dans-un-gaz-de-fermions-phonons-et-plasmons-du-regime-hydrodynamique-au-regime-non-collisionnel-thomas-repplinger-lpt-these-12-12-2024-15h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,HDR / Thesis,LPT
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241217T140000
DTEND;TZID=Europe/Paris:20241217T153000
DTSTAMP:20260413T182631
CREATED:20241209T083523Z
LAST-MODIFIED:20241212T101054Z
UID:11188-1734444000-1734449400@fermi.univ-tlse3.fr
SUMMARY:Aucun boson n’est une île. - (Louis Garbe / LPT / Seminar). - 17/12/2024\, 14H
DESCRIPTION:Séminaire LPT \nLouis Garbe (Université technique de Munich) \nSeminar LPT\, 17/12/2024\, 14H\, 3R4\, salle de conférence \nSummary\nQuantum effects in transport are often associated with spatial coherence properties\, ie\, the ability of a particle to delocalize across several lattice sites. In this talk\, I will argue that non-trivial effects can also be observed in the absence of spatial coherence\, in particular signatures of the particle statistics. When bosons (fermions) hop incoherently on a lattice\, jumps to an occupied sites are amplified (supressed)\, even when the particles do not directly interact. \nI will present a few consequences of this effect for the transport of bosons\, through a model called Asymmetric Simple Inclusion Process (ASIP). In particular\, I will show how this Bose-enhancement of jumps to occupied sites leads to a complex non-linear dynamics\, that can be connected to topics as varied as lasing theory\, Kardar-Parisi-Zhang physics\, non-hermitian hamiltonians\, and self-pulsing in excitable systems. I will also discuss how these effects may be observed in superconducting circuit architecture.
URL:https://fermi.univ-tlse3.fr/event/aucun-boson-nest-une-ile-louis-garbe-lpt-seminar-17-12-2024-14h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,LPT,Seminars
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