Fig. 1: Excitation and down-conversion scheme.

Two-photon excitation from the ground state \(|G\rangle\) to the biexciton state \(|B\rangle\) and stimulated down-conversion (SDC) to a virtual state by a control laser-field. The energy of the spontaneous SDC emission is defined by the energies of the state \(|B\rangle\) and the control-laser energy and detuned from the cascaded decay via the exciton state \(|X\rangle\).