Evolution of linear and nonlinear optical responses in single- and double-dressing quadphoton correlations

Research on entangled multipartite systems with controllable wave functions has attracted significant interest in the field of quantum optics. For quantum communications and quantum information processing, linear and nonlinear optical susceptibilities govern high-order correlations and entangled multiple-photon resources. In single- and double-dressing quadphoton correlations, we have observed the evolution of linear and nonlinear optical responses in the group delay and Rabi oscillation regimes. In the group delay regime, when linear susceptibility is evident, the quadphoton coincidence counting rate exhibits a rectangular profile. In the Rabi oscillation regime, the enhanced nonlinear susceptibility induced by strong laser dressing effects control quadphoton wave packets based on damped Rabi oscillation. Additionally, at different delay times, some photons exist in the group delay regimes, while others exist in the Rabi oscillation regimes, suggesting a coexistence mechanism. Additionally, there is a transition regime in which a portion of the photons are in both the group delay and Rabi oscillation regimes. By varying the power of the dressing field and optical depth, we realized the evolution between these two regimes for entangled quadphotons. Additionally, we demonstrate the shortening of coherence times under double-dressing conditions compared to single-dressing conditions. These results can help improving the length of coherence time and information capacity, which have great significance for the future development of long-distance and long coherent time quantum communication and quantum storage.