  The ultrafast detection of single photons is currently restricted by the
limited time resolution (a few picoseconds) of the available single-photon
detectors. Optical gates offer a faster time resolution, but so far they have
been mostly applied to ensembles of emitters. Here, we demonstrate through a
semi-analytical model that the ultrafast time-resolved detection of single
quantum emitters can be possible using an optical-Kerr-shutter (OKS) at GHz
rates under focused illumination. This technique provides sub-picosecond time
resolution, while keeping a gate efficiency at around 85 \%. These findings lay
the ground for future experimental investigations on the ultrafast dynamics of
single quantum emitters, with implications for quantum nanophotonics and
molecular physics
