Beyond the HOM dip: a multi-metric module for teaching two-mode quantum optical interference

The Hong-Ou-Mandel (HOM) effect is often introduced through a single benchmark: coincidence suppression for |1⟩ ⊗ |1⟩ at a balanced beam splitter. We present a classroom-oriented instructional module that broadens this treatment by comparing three output metrics-on/off coincidence probability P c , cross-correlation g (2) 12 , and noise-reduction factor NRF-across four input families: Fock, superposition, coherent, and squeezed light. The module targets three instructional challenges in upper-division quantum optics: treating interference quality as a single observable, weakly connecting quantum-classical distinctions to output statistics, and limiting transfer from two-mode HOM reasoning to broader photonic benchmarking questions. A common beam-splitter sweep shows that different metrics probe different statistical properties of the same output state and can therefore support different source choices depending on the physical objective. The module combines a Jupyter/QuTiP simulator, guided activities, specification-style summary tables, and a grading rubric for use in a single upper-division or early graduate class meeting.