STAGE ULTRA COLD ATOMS IN A QUANTUM GRAVIMETER

Date de mise à jour de l’offre

Systèmes de Référence Temps-Espace (SYRTE :

Situé à l’Observatoire de Paris, le SYRTE - Systèmes de Référence Temps-Espace - est une unité mixte de recherche (UMR 8630) du CNRS, de l’Observatoire de Paris - Université PSL et de Sorbonne Université. Alliant recherche de très haut niveau et services scientifiques, le SYRTE se place aujourd’hui au premier rang international dans des champs disciplinaires variés : métrologie du temps et des fréquences, systèmes de référence célestes, rotation de la Terre, histoire de l’astronomie. La pluridisciplinarité du SYRTE se retrouve aussi dans ses compétences transverses - théorie, instrumentation, traitement et analyse de données - et dans la diversité de ses objectifs qui vont de la physique fondamentale jusqu’au transfert industriel.

Description de la mission

We have developed at SYRTE a state of the art cold atom gravimeter (CAG), whose principle of operation is based on atom interferometry techniques. It uses free-falling 87Rb atoms, which experience a sequence of Raman pulses
driven by counter-propagating vertical lasers. This creates an atom interferometer, whose phase shift is proportional
to g, the Earth gravity acceleration. Our instrument measures g with a sensitivity better than conventional state of the art absolute gravimeters, with a record sensitivity of 5.7 10-9g at 1s, limited by residual vibrations. After averaging, we sometimes reach statistical uncertainties in the low 10-10g range.
We have recently implemented on the setup a crossed dipole trap with a high power fiber laser at 1.5 µm, in which we prepare ultracold atoms by evaporative cooling. We routinely produce samples of ultracold atoms, with
temperatures in the 50 nK-10 µK range, and with much higher densities. Using this new source, we have recently improved the accuracy of the measurement of gravity by tackling the dominant systematic effects: Coriolis acceleration and wavefront distortions of the Raman lasers. Both effects being related to the motion of the atoms in the interferometer laser beams profile, the reduced expansion of the ultracold atoms allowed us to reduce the uncertainty in the evaluation of these effects by a factor of 3, down to 1.3 10-9g, in a first series of interferometer measurements. This makes the CAG the more accurate gravimeter. Limits have been identified and several improvements will be made to reach the CAG in the 10-10g domain both in term of accuracy and sensitivity.

Profil recherché

The ultimate aim is to improve the evaluation of Coriolis acceleration and wavefront distortions effects even further, by performing measurements at very low temperature, and with more atoms. This will require to optimize the
evaporation sequence, by increasing the capture volume of the trap using modulation techniques. Yet, a drawback when using dense samples of ultracold atoms, eventually Bose-Einstein condensed, instead of a more dilute laser
cooled source, arises from the effect of interatomic interactions, which are expected in our configuration to impart small biases to the measurement. The intern will take advantage of the well-controlled environment of our
gravimeter to carry a detailed investigation of this new systematic effect.
Coupled with the dipole trap and the reflexion system, the CAG measurement will reach the unprecedented performances which will make our instrument the best standard in absolute gravimetry worldwide. It will be compared to other technology and be used

Niveau de qualification requis

Bac + 4/5 et +
  • Employeur
    Systèmes de Référence Temps-Espace (SYRTE
  • Secteur d’activité de la structure
    Enseignement - Formation - Recherche
  • Effectif de la structure
    De 51 à 250 salariés
  • Site internet de la structure
    https://syrte.obspm.fr
  • Type de stage ou contrat
    Stage pour lycéens et étudiants en formation initiale
  • Date prévisionnelle de démarrage
  • Durée du stage ou contrat
    Plus de 4 mois et jusqu'à 6 mois
  • Le stage est-il rémunéré ?
    Oui
  • Niveau de qualification requis

    Bac + 4/5 et +
  • Lieu du stage
    61, avenue de l’Observatoire,
    75014 PARIS 14E ARRONDISSEMENT
  • Accès et transports
    https://www.obspm.fr/acces-au-site-de-paris.html