These experiments investigate the properties of pairs of entangled photons.  We generate entangled pairs of 915.8-nm photons through type-II parametric downconversion by sending a beam of 457.9-nm light through a BBO crystal.  These photons are detected using two avalanche photodiodes.  Polarization-entangled photons are created in a way such that the two entangled photons, when  detected, are shown to always have either identical or orthogonal polarizations.  However, before a measurement is performed on either of these photons, neither occupies a distinct polarization state.  Instead each photon of the pair exists in a superposition of two possible polarization states.  As soon as one photon of the pair hits a polarizer, both photons are snapped into definite states.