Rydberg blockade, F\"orster resonances, and quantum state measurements with different atomic species

We calculate interspecies Rydberg-Rydberg interaction strengths for the heavy alkalis Rb and Cs. The presence of strong F"orster resonances makes interspecies coupling a promising approach for long range entanglement generation. We also provide an overview of the strongest F"orster resonances for Rb-Rb and Cs-Cs using different principal quantum numbers for the two atoms. We show how interspecies coupling can be used for high fidelity quantum non demolition state measurements with low crosstalk in qubit arrays.