Noise-enhanced Ballistic Expansion of Polariton Wave-packets in a Multimode Cavity

Advances in optical measurements enable precise tracking of cavity polariton wave-packets across broad spatial and temporal ranges, but how dephasing reshapes their real-space dynamics over multiple time scales remains unclear. Here we show, using a stochastic multimode Tavis-Cummings model, that dephasing noise leads to a robust hierarchy of dynamical regimes comprising Rabi oscillation damping, center-of-mass slowdown, population relaxation, and ballistic-to-diffusive crossover, in the order of increasing time scales. We further predict that dephasing can enhance ballistic spreading and sustain it far beyond the microscopic dephasing time by two orders of magnitude. These predictions agree with recent microscopy measurements and provide experimentally testable guidance for engineering energy transport in polaritonic platforms.