Reducing system dimensionality with long-range collective dipole-dipole interactions

Dimensionality plays a crucial role in long-range dipole-dipole interactions (DDIs). We demonstrate that a resonant nanophotonic structure modifies the apparent dimensionality in an interacting ensemble of emitters, as revealed by population decay dynamics. Our measurements on a dense ensemble of interacting quantum emitters in a resonant nanophotonic structure with long-range DDIs reveal an effective dimensionality reduction to $\bar{d} = 2.20 (12)$, despite the emitters being distributed in 3D. This contrasts the homogeneous environment, where the apparent dimension is $\bar{d} = 3.00$. Our work presents a promising avenue to manipulate dimensionality in an ensemble of interacting emitters.