Unraveling the time cross correlations of an emitter switching between two states with the same fluorescence intensity

The autocorrelation function of the fluorescence intensity of a nanoemitter is measured with the standard Hanbury-Brown and Twiss setup. Time-tagging of the photodetection events during all the experiment has opened new possibilities in terms of post-selection techniques that enable to go beyond the blinking and antibunching characterization. Here, we first present a new method developed to investigate in detail the antibunching of a fluorophore switching between two emitting states. Even if they exhibit the same fluorescence intensity, their respective amount of antibunching can be measured using the gap between their respective decay rates. The method is then applied to a nanoemitter consisting in a colloidal quantum dot coupled to a plasmonic resonator. The relative quantum efficiency of the charged and neutral biexcitons are determined.