Rydberg atoms

The strong interaction between individual Rydberg atoms provides a powerful tool exploited in an ever-growing range of applications in quantum information science, quantum simulation and ultracold chemistry. The starting point of this project was that more and more experiments are probing this interaction at short atomic distances or with such high precision that perturbative calculations as well as restrictions to the leading dipole–dipole interaction term are no longer sufficient. We wrote a tutorial, reviewing all relevant aspects of the full calculation of Rydberg interaction potentials such as the derivation of the interaction Hamiltonian from the electrostatic multipole expansion, numerical and analytical methods for calculating the required electric multipole moments, and the inclusion of electromagnetic fields with arbitrary direction. Our software for calculating Rydberg potentials including all features discussed in this tutorial is available as open source.