  We investigate the cross-interactions in a two-component polariton quantum
fluid coherently driven by two independent pumping lasers tuned at different
energies and momenta. We show that both the hysteresis cycles and the ON/OFF
threshold of one polariton signal can be entirely controlled by a second
polariton fluid. Furthermore, we study the ultrafast switching dynamics of a
driven polariton state, demonstrating the ability to control the polariton
population with an external laser pulse, in less than a few picoseconds.
