2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/124234We developed a quantum theory for degenerate $χ^{(3)}$ two-photon state generated from optical fiber, and compared the theory predictions with an experimental result which exhibits a Hong-Ou-Mandel dip visibility of around 94%. Excellent agreement between theory and experiment has been achieved, and we attribute the missing 6% visibility mainly to spatial mode mismatch between signal and idler photons at the beamsplitter.8 pages, 3 figuresQuantum Physicstext