Switchable dynamic Rydberg-dressed excitation via a cascaded double electromagnetically induced transparency

Dynamic control of atomic dressing to the highly excited Rydberg state in multilevel systems has special appeals owing to the development of flexible and precise measurement. In this study we develop an experimentally accessible proposal to robustly control the dressing probability via a three-step cascaded excitation with double electromagnetically induced transparency (EIT) technique. The system can function as an optical switch where the third addressing laser serving as the control knob can switchably engineer the dressing probability with time. Differing from a conventional two-photon EIT, this scheme facilitates a maximal dressing probability determined by a relative strength between two strong coupling fields, entirely relaxing their absolute values. The collective feature caused by the interactions of a few atoms is also studied leading to an enhanced dressing probability as well as reduced response times. Our work offers the opportunity to a coherent dynamic control of Rydberg excitation and to realize sizable Rydberg-Rydberg interactions in weakly driven multilevel quantum systems.