We have two experimental setups where we study of the effects of strong dipole-dipole interactions in systems of a few atoms:
- In the Rydberg project (CHADOQ), we use arrays of optical tweezers, each containing a single Rb atom, and we induce strong interactions between the atoms by exciting them to Rydberg states. We have basically full control over the system: geometry and size of the array, exact number of atoms, strength of the interaction… With this platform, we are currently exploring the physics of spin Hamiltonians with up to 50 particles.
- In the Nanocloud project (CYCLOPIX), we trap an adjustable number of Rb atoms (up to ~ 300) in the same microscopic dipole trap. The size of the cloud is comparable to the resonance wavelength of Rb and thus the optical response of the cloud features collective effects, due to the strong interaction between light-induced dipoles.
- In the vapor cell project, we study the optical response of a hot (100°C – 200°C) vapor of alkali confined in a cell with thickness ranging from almost zero to one micrometer, i.e. comparable to the wavelength of an optical transition in Rb, Cs or K. Using this system, we study the role of the atom-surface interaction, the dipole-dipole interactions between atoms or their motion on the optical properties of the vapor. Our optical workshop has build by all optical bonding a new type of cell with superpolished windows. We run this project in collaboration with the group of Charles Adams and Ifan Hughes in Durham (UK).