This means that so many electrons were pumped up into an excited state by the laser that more were in that excited state than in their normal, unexcited state.
When the polariton flow was excited with two laser beams, the quantum fluid began to oscillate backwards and forwards in ways predicted by quantum mechanics.
Once that is done, another laser pulse will jostle the virus from its ground state into an excited state, just as a single atom is excited by moving one of its electrons from a lower to a higher orbital.