Quantifying the Impact of State Mixing on the Rydberg Excitation Blockade

The Rydberg excitation blockade has enabled impressive achievements in quantum information and simulation.  However, unwanted processes may compromise the single-excitation behavior of the blockade and reduce its efficiency.  We study one such process, state-mixing interactions.  When ultracold atoms are excited to Rydberg states near Förster resonance, up to ∼ 50% of the detected atoms can be found in dipole coupled product states within tens of ns of excitation. There has been disagreement in the literature regarding the mechanism by which this mixing occurs.   We use state-selective field ionization spectroscopy with single-event resolution to probe state mixing near the 43D_5/2 Förster resonance in Rb.  Our method allows us to quantify both the number of additional excitations added by each mixing event, as well as the extent to which state mixing “breaks” the blockade.