A demonstration of quantum key distribution with single photons for the undergraduate laboratory

The goal of this work was to create a laboratory experiment feasible in an undergraduate setting that demonstrates quantum key distribution and security attacks on quantum key distribution using single photons. The basic principle behind this experiment is that when a measurement is made on a quantum state, it modifies the information it conveys. This principle has been extended to quantum secure communications and is a teaching moment for physicists, computer scientists and engineers alike. We mimicked Eve or the eavesdropper by using an intercept and resend method, which include using an interferometer and a quartz plate. We used polarization entangled photons produced by parametric down-conversion.