Quantum optics with interacting polaritons

Arturo Camacho-Guardian, M. A. Bastarrachea-Magnani, Thomas Pohl +1 more

The hybridization of light and matter excitations in the form of polaritons has enabled major advances in understanding and controlling optical nonlinearities. Entering the quantum regime of strong interactions between individual photons has, however, remained challenging since the strength of achievable polariton interactions is typically limited by the available interactions in the material. Here, we investigate collisions between dark-state polaritons in three-level systems and discover a resonant process that yields effective interactions, which are much larger than the underlying interaction between their matter constituents. We systematically investigate the underlying mechanism and demonstrate a substantial enhancement of polariton interactions by several orders of magnitude. This suggests a promising approach to quantum nonlinear optics in a range of physical settings, from atomic gases to excitons in semiconductors and two-dimensional bilayer materials.

Harry J. Kimble, O. Carnal, N. Ph. Georgiades +7 more

C. S. Hofmann, G. Günter, H. Schempp +5 more

We observe individual dark-state polaritons as they propagate through an ultracold atomic gas involving Rydberg states coupled via an electromagnetically induced transparency resonance. Strong long-range interactions between Rydberg excitations give rise to a blockade between polaritons, resulting in large optical nonlinearities and modified polariton number statistics. By combining optical imaging and high-fidelity detection of the Rydberg polaritons we investigate both aspects of this coupled atom-light system. We map out the full nonlinear optical response as a function of atomic density and follow the temporal evolution of polaritons through the atomic cloud. In the blockade regime, the statistical fluctuations of the polariton number drop well below the quantum noise limit. The low level of fluctuations indicates that photon correlations modified by the strong interactions have a significant backaction on the Rydberg atom statistics.

A. P. Alodjants, Sergei M Arakelyan

Ramarao Inguva

Vincenzo Savona, Dmitry N. Chigrin

I will give an overview of our recent studies on polariton quantum optics. I will show how polaritons can be produced in quantum entangled states, thanks to parametric scattering. By combining a time‐dependent density‐matrix model of the coherent polaritons, with a Boltzmann kinetics of the surrounding incoherent polariton gas in interaction with a thermal bath of phonons, the degree of entanglement can be quantified. It turns out that large entanglement is expected under realistic experimental conditions. I will further show how the polariton nonlinearity can be exploited to design quantum devices. As an example, I will model a system of coupled polariton modes, that operates as an efficient source of single photons by exploiting quantum interference between different pathways in the time evolution of the quantum field.