Observation of period doubling in a strongly driven single spin system in diamond

Unraveling the quantum dynamics in non-equilibrium settings remains a significant challenge in modern physical sciences. Systems driven out of equilibrium can exhibit a diverse range of phenomena, including self-organized synchronization and dynamical phase transitions. In this work, we report the observation of period doubling in driven spin systems utilizing a single nitrogen-vacancy (NV) center in diamond. The dynamics of a two-level system, modeled by a standard Hamiltonian driven by a linearly polarized sinusoidal field, demonstrate period doubling under specific driving conditions. In the Rabi regime, the spin population is approximately described by sinusoidal oscillations at the Rabi frequency; however, stronger drive amplitudes lead to deviations from this behavior, revealing phenomena such as period n-tupling. We specifically observe period doubling in the dynamics of a single NV center driven at resonance with the lowest period doubling amplitude. This study provides valuable insights into manipulating quantum states in driven spin systems and presents a potential pathway for controlling quantum systems with periodic drive fields.