  We report on the resonant emission in coherently-driven single semiconductor
quantum dots. We demonstrate that an ultra-weak non-resonant laser acts as an
optical gate for the quantum dot resonant response. We show that the gate laser
suppresses Coulomb blockade at the origin of a resonant emission quenching, and
that the optically-gated quantum dots systematically behave as ideal two-level
systems in both regimes of coherent and incoherent resonant emission.
