It is shown that EPR correlations are the angular analogue to the Hanbury-Brown--Twiss effect. As insight provided by this model, it is seen that, analysis of the EPR experiment requires conditional probabilities which do not admit the derivation of Bell inequalities.
The Hanbury Brown-Twiss (HBT) effect marked a significant milestone in quantum optics by illustrating that intensity correlations can reveal inherently quantum features of light. Motivated by the structure of the original 8-mode HBT interferometer, we develop a simplified 4-mode toy-model that captures its essential physical ingredients while significantly reducing analytical complexity. Our toy-model provides an intuitive and well-structured framework for examining the desired correlation functions. We investigate whether our toy-model can exhibit genuinely non-classical behaviour by formulating and applying a Bell-type inequality tailored to its specific measurement configuration. Our analysis shows that the correlations generated by the toy-model violate the inequality, indicating the presence of non-local features that are incompatible with any classical hidden-variable description. The results highlight the power of simplified models in uncovering fundamental aspects of non-classicality in optical systems.