Splitting of the three-body Förster resonance in Rb Rydberg atoms as a measure of dipole-dipole interaction strength

Three-body Förster resonances controlled by a dc electric field are of interest for the implementation of three-qubit quantum gates with single atoms in optical traps using their laser excitation into strongly interacting Rydberg states. In our recent theoretical paper [Zh. Eksper. Teor. Fiz. 168(1), 14 (2025)] it was found that the proposed earlier three-body Förster resonance $3\times nP_{3/2} \to nS_{1/2} +(n+1)S_{1/2} +nP_{1/2} $ in Rb Rydberg atoms has a splitting, with one of the split components having weaker dependence of the resonant electric field (and the corresponding dynamic shift) on the distance $R$ between the atoms. Here we study this effect in more detail, since such a resonance is the most suitable for performing experiments on observing coherent oscillations of populations of collective three-body states and implementing three-qubit quantum gates based on them. For a linear spatial configuration of three interacting Rydberg atoms, the physical mechanism of this phenomenon is revealed and analytical formulas are obtained that describe the behavior of split structure of the Förster resonance depending on $R$. It is found that the splitting is a measure of the energy of the resonant dipole-dipole exchange interaction with an excitation hopping between neighboring Rydberg states $S$ and $P$.