Colloquium de l'INPHYNI: Wadad Zeidan (Optique quantique)/Félix Nati GUDIN (Photonique)

Wadad Zeidan - Engineering and measuring multimode entanglement in the continuous variable regime.

We generate and engineer highly multimodal quantum states of light by controlling the frequency correlations produced in nonlinear crystals via the process of parametric down conversion. By tailoring the spectral envelope of the pump field sent to the crystal, we directly shape the resulting quantum correlation functions between frequency modes. This approach allows precise control over the structure
and dimensionality of the generated states, enabling applications across quantum information processing and communication.

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Félix Gudin - Revisiting heterodyne detection for stellar interferomtry

Heterodyne interferometry offers a promising way to combine large numbers of widely separated telescopes without requiring interferometric optical-path stabilization of faint stellar signals. Originally proposed in the thermal infrared in the late 90s, this technique can achieve extreme angular resolutions but remains limited at optical wavelengths by an inherently low signal-to-noise ratio. We present a new detection concept that overcomes these limitations by using a chirped, mode-locked femtosecond laser as the local oscillator. The resulting prototype reaches a sensitivity compatible with astronomical flux levels using short integration times (10–100 ms).