Generating and detecting entangled atomic states using light

Light is a powerful tool to manipulate atoms, but it also allows to create correlations between them.

This can be achieved in optical cavities where the interaction through specific light modes is favored, or in free space where dipole-dipole interactions emerge from the continuum of electromagnetic modes available to the emitters. This coupling does not only allow for photon exchange between the atoms, but it also manifests in a cooperative spontaneous emission phenomenon. Introduced by Dicke in the 50', superradiance has since then been reported in many fields well beyond atomic physics.

I here focus on the dark side of superradiance, that is, subradiance. These very slow decaying modes correspond to non-symmetric atomic modes which couple weakly to the surrounding electromagnetic vacuum modes, and allow one to preserve the excitations stored over long times in the atomic ensembles. I will discuss how these modes can be generated efficiently in large atomic ensembles, but also how cooperative spontaneous emission here leads to atomic entangled states. Furthermore, an entanglement witness is introduced, based on macroscopic measurements of the electric field, which is able to detect the entangled nature of these states, as well as other Dicke states.

[1] Subradiance with saturated atoms: population enhancement of the long-lived states, A. Cipris, N.A. Moreira, T.S. do Espirito Santo, P. Weiss, C.J. Villas-Boas, R. Kaiser, W. Guerin, R. Bachelard, Phys. Rev. Lett. 126 (10), 103604 (2021)

[2] Generating long-lived entangled states with free-space collective spontaneous emission, A. C. dos Santos, A. Cidrim, C. J. Villas-Boas, R. Kaiser, R. Bachelard, Phys. Rev. A 105, 053715 (2022)

[3] Detecting entanglement from macroscopic measurements of the electric field and its fluctuations, P. Rosario, A. C. Santos, N. Piovella, R. Kaiser, A. Cidrim, R. Bachelard, Physical Review Letters 133, 050203 (2024)