Exploiting separation-dependent coherence to boost optical resolution

The problem of resolving pointlike light sources not only serves as a benchmark for optical resolution but also holds various practical applications ranging from microscopy to astronomy. In this study, we aim to resolve two thermal sources sharing arbitrary mutual coherence using the spatial mode demultiplexing technique. Our analytical moment-based approach covers scenarios where the coherence and the emission rate of the sources depend on the separation between them, and is not limited to the Poissonian approximation. Studying the examples of the interactive dipoles imaging and imaging of the reflective particles under external illumination, we demonstrate that separation-dependent coherence, which arises in this scenario, can significantly enhance optical resolution. We show that this effect is robust in the presence of the emitters dephasing and detection noise.