Isolating Pure Quadratic Zeeman Splitting

Nonlinear magnetic interactions provide access to complex quantum spin dynamics and thus enable the study of intriguing physical phenomena. However, these interactions are often dominated by the linear Zeeman effect, which can complicate system dynamics and make their analysis more challenging. In this article, we theoretically and experimentally introduce a method to induce the quadratic Zeeman effect while effectively compensating for its linear counterpart. By isolating the quadratic Zeeman contributions, we demonstrate and analyze controlled superposition generation between specific magnetic sublevels in room-temperature rubidium-87 atoms. This study opens avenues for controlling any spin system, regardless of its total angular momentum, which we plan to explore further in the context of quantum-state tomography and engineering (e.g., spin squeezing).