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We present detailed instructions for constructing and operating an apparatus to produce and detect polarization-entangled photons. The source operates by type I spontaneous parametric downconversion in a two-crystal geometry. Photons are detected in coincidence by single-photon counting modules and show strong angular and polarization correlations. We observe more than 100 entangled photon pairs per second. A test of a Bell inequality can be performed in an afternoon. [DOI: 10.1119/1.1498859]

We use polarization-entangled photon pairs to demonstrate quantum nonlocality in an experiment suitable for advanced undergraduates. The photons are produced by spontaneous parametric downconversion using a violet diode laser and two nonlinear crystals. The polarization state of the photons is tunable. Using an entangled state analogous to that described in the Einstein-Podolsky-Rosen paradox, we demonstrate strong polarization correlations of the entangled photons. Bell's idea of a hidden variable theory is presented by way of an example and compared to the quantum prediction. A test of the Clauser, Horne, Shimony, and Holt version of the Bell inequality finds S = 2.307 [+ or -] 0.035, in clear contradiction of hidden variable theories. The experiments described can be performed in an afternoon. [DOI: 10.1119/1.1498860]