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Présentation du LCAR
Le LCAR (UMR 5589, Laboratoire Collisions-Agrégats-Réactivité) est un laboratoire de physique fondamentale localisé sur le campus de l'Université Toulouse III Paul Sabatier. Le LCAR est membre de la Fédération FeRMI (Fédération de recherche Matière et Interactions). Deux axes principaux sont développés:
- L’axe « interaction laser-matière » se focalise sur la manipulation par laser d’ondes de matières et l’étude d’effets fondamentaux.
- L’axe « Structures et dynamiques moléculaires » développe l’étude et la mesure de propriétés de systèmes complexes tels que des agrégats, des nanoparticules ou des molécules d’intérêt biologique et astrophysique dans leur environnement.
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Photoionization as a half-scattering process is not instantaneous. Usually, time delays in photoionization are on the order of tens of attoseconds. In going from a single atom to a nano-object, one can expect the delay to increase, since the photoelectron scatters over a larger distance. Here we show that this intuition is not correct when comparing three-dimensional and planar molecules. Using attosecond interferometry, we find that the time delays in two-dimensional (2D) carbon-based molecules can be significantly shorter than those of three-dimensional counterparts. The measured time delay carries the signature of the spatial distribution of the 2D hole created in the residual molecular cation, allowing us to obtain its dimensions with angstrom accuracy. Our results demonstrate that the photoionization delay depends on the symmetry and shape of the created hole, as we show by identifying a quadrupole contribution in the measured delay of 2D molecules.
Optimal control is a valuable tool for quantum simulation, allowing for the optimized preparation, manipulation, and measurement of quantum states. Through the optimization of a time-dependent control parameter, target states can be prepared to initialize or engineer specific quantum dynamics. In this work, we focus on the tailoring of a unitary evolution leading to the stroboscopic stabilization of quantum states of a Bose-Einstein condensate in an optical lattice. We show how, for states with space and time symmetries, such an evolution can be derived from the initial state-preparation controls; while for a general target state we make use of quantum optimal control to directly generate a stabilizing Floquet operator. Numerical optimizations highlight the existence of a quantum speed limit for this stabilization process, and our experimental results demonstrate the efficient stabilization of a broad range of quantum states in the lattice.
Protonated mixed pyrene-water clusters, (Py) m (H 2 O) n H + , where m=[1-3] and n=[1-10], are generated using a cryogenic molecular cluster source. Subsequently, the mass-selected mixed clusters undergo controlled collisions with rare gases, and the...
This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more km-scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions.
We report here on the realization of light-pulse atom interferometers with large-momentum-transfer atom optics based on a sequence of Bragg transitions. We demonstrate momentum splitting up to 200 photon recoils in an ultracold atom interferometer. We highlight a new mechanism of destructive interference of the losses leading to a sizable efficiency enhancement of the beam splitters. We perform a comprehensive study of parasitic interferometers due to the inherent multiport feature of the quasi-Bragg pulses. Finally, we experimentally verify the phase shift enhancement and characterize the interferometer visibility loss