Laboratoire Charles Fabry, Institut d’Optique Graduate School
Continuous-wave superradiant laser
We have perfected methods to detect cold atom clouds released from a trap in three dimensions and with single atom sensitivity. We have been using this method to perform fundamental experiments on correlations and entanglement produced by non-linear processes in Bose-Einstein condensates. An example is our observation of the Hong-Ou-Mandel effect 
The group has recently developed a two-particle interferometer in momentum space , see figure. Starting from a two-particle entangled state, |p,-p〉 + |p’,-p’〉, this configuration can test a Bell inequality. This would be the first time that such inequalities have been tested for the motional degrees of freedom of freely falling, massive particles.
To perform a Bell test in this configuration, it is necessary to have interferometric phase control of the paths in the interferometer. A first part of the internship will be to implement the phase control and check it on a standard one-particle interferometer. Preliminary experiments are underway to optimize the stability and speed to produce the expected entangled state; the intern will participate in it. He/she will then participate in the Bell experiment i.e. acquisition of the data and its analysis.
We use a non-linear process in a Bose-Einstein condensate to produce entangled atom pairs reminiscent of four-wave mixing in optics. The condensate is loaded in a moving optical lattice. The band structure of the lattice modifies the dispersion relations of the atoms so that correlated atom pairs are produced spontaneously. This process is slightly multi-mode and therefore the resulting state is multi-particle entangled. An extension of the proposed scheme to look at entanglement on a larger set of modes is also envisioned.
 R. Lopes et al., Nature 520, 66 (2015) and M. Perrier et al., SciPost 7, 002 (2019)
 P. Dussarrat et al., Phys. Rev. Lett. 119, 173202 (2017)
METHODS AND TECHNIQUES
The internship will involve several methods pertaining to the domains of Bose-Einstein condensation and atom interferometry. Many experimental techniques will be used including, optics, electronics, automoted data acquisition and numerical simulation.
Group webpage and recent publications: https://www.lcf.institutoptique.fr/groupes/gaz-quantiques
Work place : Laboratoire Charles Fabry de l’Institut d’Optique, 2 avenue Augustin Fresnel, Palaiseau, France
Tel: +33(0)1 64 53 33 52