Abstract
External driving of spins by magnetic or optical fields in different systems underpins numerous applications ranging from magnetic resonance imaging to coherent state control in quantum computing. Here, we reveal the effect of an all-optically driven spin precession in microcavity polariton condensates. It is achieved through a radio frequency modulation of a spatially rotating, asymmetric exciton reservoir that both confines and actively replenishes the polariton condensate. The non-resonant stirring profile is realized by the beating note of two structured and frequency-detuned laser beams. We realize the GHz driven spin precession with striking phase stability, which occurs only in the resonance with the internal condensate self-induced Larmor precession frequency. From the shape of the revealed resonance, we estimate the spin coherence time (T2) for the polariton condensate. Our observations are supported by numerical simulations and evidence a quantum fluidic analogue of the nuclear magnetic resonance effect.