Demonstrating quantum entanglement and Hong-Ou-Mandel effect, using type-II spontaneous parametric down conversion with C programming for data collection

Spontaneous parametric down conversion (SPDC) is used to generate quantum entangled photons through a non-linear crystal. The entanglement of photons is demonstrated by observing the effects of indistinguishability on photons, first through time and energy, then by polarization. The Hong-Ou-Mandel (HOM) effect was also demonstrated. A theoretical derivation of the effect of a non 50/50 beam splitter (BS) is also investigated. The energy of the photons was changed by varying the temperature of the crystal whilst the time difference was changed by varying the relative position of two mirrors. Results showed a clear effect from indistinguishability on both energy and time