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DTSTART;TZID=Europe/Paris:20250902T140000
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DTSTAMP:20260612T151433
CREATED:20250902T060030Z
LAST-MODIFIED:20250902T091512Z
UID:11624-1756821600-1756827000@fermi.univ-tlse3.fr
SUMMARY:NOFT: Une méthode efficace pour les fortes corrélations. - (Ion Mitxelena / LPT / Seminar). - 2/09/2025\, 14H
DESCRIPTION:Séminaire LPT \nIon Mitxelena (Université du Pays basque) \nSeminar LPT\, 2/09/2025\, 14H\, 3R4\, salle de conférence \nSummary :\nSince the non-relativistic Hamiltonian operator contains only one- and two-electron operators\, the energy of an electron system in the non-relativistic Born-Oppenheimer approximation can be determined exactly from the knowledge of the one- and two-particle reduced density matrices (1- and 2-RDMs)\, much simpler objects than the wavefunction. Accordingly\, one can employ the exact functional with an approximate 2-RDM that is built from the 1-RDM using a reconstruction functional. The major advantage of a 1-RDM formulation is that the kinetic energy is explicitly constructed and does not require a functional\, in contrast to DFT. \nThe 1-RDM functional is called Natural Orbital Functional (NOF) [1\,2] when it is based upon the spectral expansion of the 1-RDM. In this presentation\, the theory behind the NOFT based approximations\, PNOF5\, PNOF7\, and GNOF\, is outlined\, and some challenging examples are\npresented. Special emphasis is put on strong correlation problems [3]\, where the latter offer an interesting alternative to CASSCF and CASPT2 approaches since the selection of an active space is not required. Recent calculations are presented to illustrate the performance of the aforementioned methods. \nLastly\, we present DoNOF [4]\, the first publicly available open-source software to run NOF calculations\, as well as its current capabilities and limits from both computational and accuracy perspectives. \n[1] M. Piris\, Adv. Quantum Chem. 90\, 1-52 (2024) (Review on NOFT) \n[2] K. Pernal & K. J. H. Giesbertz\, Top. Curr. Chem. (2015) (Review on RDMFT) \n[3] I. Mitxelena’s thesis on NOFT for strong correlation \n[4] M. Piris and I. Mitxelena\, Comp. Phys. Comm. 259\, 107651 (2021) \n[5] I. Mitxelena\, J. F. H. Lew-Yee and M. Piris\, to be published
URL:https://fermi.univ-tlse3.fr/event/noft-une-methode-efficace-pour-les-fortes-correlations-ion-mitxelena-lpt-seminar-2-09-2025-14h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250905T110000
DTEND;TZID=Europe/Paris:20250905T120000
DTSTAMP:20260612T151433
CREATED:20250902T082823Z
LAST-MODIFIED:20250903T121403Z
UID:11643-1757070000-1757073600@fermi.univ-tlse3.fr
SUMMARY:Simulation de systèmes de matière condensée avec des ordinateurs quantiques. - (Lex Kemper / LPT / Seminar). - 5/09/2025\, 11H
DESCRIPTION:Séminaire LPT \nLex Kemper (Université d’État de Caroline du Nord) \nSeminar LPT\, 5/09/2025\, 11H\, 3R4\, salle de conférence \nSummary \nIn this talk\, I’ll present our recent advances in using quantum computers to simulate condensed matter systems\, focusing on spectroscopic experiments in and out of equilibrium. \nFirst\, I’ll introduce a linear response framework that directly connects experimental observables to quantum many-body states by computing bosonic and fermionic correlation functions on a quantum computer. Unlike prior methods\, our approach supports multiple operators in a single circuit\, enabling efficient and simultaneous extraction of various correlation functions without extra ancilla qubits. We demonstrate this on a charge-density-wave material using IBM’s ibm_auckland device\, showing robust results even on noisy hardware. This method streamlines spectroscopic simulations and opens new directions for improving classical approaches. \nSecond\, I’ll discuss simulating open quantum systems on noisy quantum hardware. We find that such systems are surprisingly robust to hardware errors—even with deep circuits—making them promising candidates for near-term simulations. \nTogether\, this work demonstrates the feasibility and promise of quantum simulation for both equilibrium and non-equilibrium phenomena in complex materials.
URL:https://fermi.univ-tlse3.fr/event/simulation-de-systemes-de-matiere-condensee-avec-des-ordinateurs-quantiques-lex-kemper-lpt-seminar-5-09-2025-11h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250916T140000
DTEND;TZID=Europe/Paris:20250916T160000
DTSTAMP:20260612T151433
CREATED:20250915T073939Z
LAST-MODIFIED:20250915T100413Z
UID:11640-1758031200-1758038400@fermi.univ-tlse3.fr
SUMMARY:Extracting Subleading Asymptotics from Finite-Size Scaling in One-Dimensional Quantum Liquids. - (Oleksandr Gamayun / LPT / Seminar). - 16/09/2025\, 14H
DESCRIPTION:Séminaire LPT \nOleksandr Gamayun (London Institute for Mathematical Sciences) \nSeminar LPT\, 16/09/2025\, 14H\, 3R4\, salle de conférence \nSummary\nThe hydrodynamic framework of Luttinger liquid theory conventionally describes one-dimensional quantum liquids of bosons\, fermions\, and spins. This approach predicts power-law asymptotic behavior of the correlation functions with the exponents governed by the dimensionless Luttinger parameter and determined by the thermodynamic properties of the system. While the universal exponents are well understood\, the non-universal prefactors can be computed through finite-size scaling of form factors (matrix elements). In this talk\, I present a method that goes further\, enabling the extraction of subleading asymptotic behavior directly from the full finite-size dependence of form factors. My primary example will be the tau function in the context of one-dimensional impenetrable bosons.
URL:https://fermi.univ-tlse3.fr/event/tba-oleksandr-gamayun-lpt-seminar-16-09-2025-14h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250930T140000
DTEND;TZID=Europe/Paris:20250930T150000
DTSTAMP:20260612T151433
CREATED:20250905T121804Z
LAST-MODIFIED:20250910T072637Z
UID:11632-1759240800-1759244400@fermi.univ-tlse3.fr
SUMMARY:Transitions de phase induites par la mesure dans les systèmes fermioniques. - ( Alexander Mirlin / LPT / Seminar). - 30/09/2025\, 14H
DESCRIPTION:Séminaire LPT \nAlexander Mirlin (KIT) \nSeminar LPT\, 30/09/2025\, 14H\, 3R4\, salle de conférence
URL:https://fermi.univ-tlse3.fr/event/transitions-de-phase-induites-par-la-mesure-dans-les-systemes-fermioniques-alexander-mirlin-lpt-seminar-30-09-2025-14h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,LPT,Seminars
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