Laboratoire Charles Fabry, Institut d’Optique Graduate School

Continuous-wave superradiant laser

Avr 29, 2023


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 [1]

The group has recently developed a two-particle interferometer in momentum space [2], 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.

[1] R. Lopes et al., Nature 520, 66 (2015) and M. Perrier et al., SciPost 7, 002 (2019)
[2] P. Dussarrat et al., Phys. Rev. Lett. 119, 173202 (2017)


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:

Work place : Laboratoire Charles Fabry de l’Institut d’Optique, 2 avenue Augustin Fresnel, Palaiseau, France


C. Westbrook
+33(0)1 64 53 33 52
E-mail: christoph.westbrook(at)