Assembling a Spontaneous Parametric Down Conversion Source

Students: Eric Pritchard, Martin Mattes

Mentor: Michael Braunstein


Spontaneous parametric down-conversion (SPDC) is a process in which a nonlinear crystal is used to convert an incident photon into a pair of photons. This pair of SPDC photons conserve the energy and momentum of the incident photon and is a quantum entangled state. We assembled an optical apparatus that was designed to produce SPDC photons from a beta barium borate crystal. We used a computational program to model the propagation directions of the SPDC photons. Collimators coupled to photon detetctors were positioned according to the model and then we made small adjustments to the positions until high count rates were measured. We established futher evidence that SPDC photons were being detected by a coincidence measurement between the photon detectors. These findings suggest that this apparatus can be used in the future to perform additional experiments on non-degenerate down-converted photons, quantum entangled state, anti-bunching experiments, and experiments involving Bell’s Inequality.


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