Gnatiessoro SORO : "Quantum imaging in diffusing media"

Abstract : Since 2010, the two-photon interference phenomenon in presence of scattering medium has been widely studied. In this thesis, we address the spatial aspects of the spatial quantum correlation function between two entangled photons of high dimensionality generated through the SPDC process and detected with two EMCCD cameras. We present the principle of the entangled photons pairs generation and how the spatial quantum correlation between the SPDC beams can be measured. Then, we introduce a numerical method based on the simulation of the
biphoton wave-function in order to calculate the spatial quantum correlation function between the entangled photons transmitted through a thin or thick scattering medium and we present the experimental results. In the case of a thin scattering medium, we show that the far-field spatial quantum correlation function exhibits a speckle pattern inasmuch as the pump beam is sufficiently large in the plane of the biphoton source. For the near-field quantum correlation measurment, we show that the contrast of the speckle pattern is reduced. In the case of a thick scattering medium, we demonstrate that the spatial quantum correlation function in both spaces exhibits a structure with a very low contrast. Finally, using a SLM we demonstrate on the one hand that by using a iterative process it is possible to focus a coherent beam through a scatterer and to obtain a SNR with the same magnitude as that obtained using the transmission matrix method. On the other hand, without a thin scattering medium, we experimentally show that is possible to manipulate the spatial correlations of the entangled photons.
In presence of a scattering medium, we numerically show that it is possible to focus the spatial quantum correlations through the scatterer

Jury Composition  :

M. Fabrice DEVAUX Professeur des universités Université Bourgogne Franche-Comté PhD Director
M. Mikhail KOLOBOV Professeur des universités Université de Lille Reporter
M. Eric LANTZ Professeur des universités Université Bourgogne Franche-Comté PhD Co-director
M. Sylvain GIGAN Professeur des universités Université Pierre et Marie Curie Reporter
M. Maxime JACQUOT Professeur des universités Université Bourgogne Franche-Comté Reviewer
M. Sébastien POPOFF Chargé de recherche Institut Langevin, ESPCI Paris Reviewer

Localization : Amphithéâtre J-J Gagnepain - Institut FEMTO-ST 15B, Avenue des Montboucons 25000 Besançon