QUROPE Quantum Information Processing and Communication in Europe

Large arrays of individually controlled atoms trapped in optical tweezers are a very promising platform for quantum engineering applications. However, to date, only disordered arrays have been demonstrated, due to the non-deterministic loading of the traps. Here, we demonstrate the preparation of fully loaded, two-dimensional arrays of up to 50 microtraps each containing a single atom, and arranged in arbitrary geometries.

Many proof-of-principle platforms for quantum simulation of spin models such as the Ising model have been implemented. It has proved difficult to produce a design with sufficient flexibility to realize arbitrary geometries and variable distance, however. Here, the authors have developed a platform that achieves this flexibility with large atom numbers. The setup is based on arrays of optical microtraps. Creating spin chains with periodic boundary conditions, the authors study the dynamics of an Ising-like spin system with 30 spins.

We present an overview of our recent investigations of long-range interactions in an ultracold Cs Rydberg gas.

Cold atomic gases resonantly excited to Rydberg states can exhibit strong optical nonlinearity at the single photon level. We observe that in such samples radiation trapping leads to an additional mechanism for Rydberg excitation.

By mapping the strong interaction between Rydberg excitations in ultra-cold atomic ensembles onto single photons via electromagnetically induced transparency, it is now possible to realize a medium which exhibits a strong optical nonlinearity at the level of individual photons. We review the theoretical concepts and the experimental state-of-the-art of this exciting new field, and discuss first applications in the field of all-optical quantum information processing.