  Quantum many-body systems near phase transitions respond collectively to
externally applied perturbations. We explore this phenomenon in a laser-driven
dissipative Rydberg gas that is tuned to a bistable regime. Here two metastable
phases coexist, which feature a low and high density of Rydberg atoms,
respectively. The ensuing collective dynamics, which we monitor in situ, is
characterized by stochastic collective jumps between these two macroscopically
distinct many-body phases. We show that the statistics of these jumps can be
controlled using a dual-tone microwave field. In particular, we find that the
distribution of jump times develops peaks corresponding to subharmonics of the
relative microwave detuning. Our study demonstrates the control of collective
statistical properties of dissipative quantum many-body systems without the
necessity of fine-tuning or of ultra cold temperatures. Such robust phenomena
may find technological applications in quantum sensing and metrology.
