A hands-on introduction to quantum mechanics

At Dickinson College, we have implemented a series of experiments that are designed to expose students to the strange and fascinating world of quantum mechanics. These experiments are employed in our sophomore-level course titled \textit{Introduction to Relativistic and Quantum Physics}, our version of the traditional \textit{Modern Physics} course. The experiments make use of a correlated light source produced via the process of Spontaneous Parametric Down Conversion (SPDC). Using such a light source, students can experimentally verify that when a single photon is incident on a beam splitter, the photon is either transmitted or reflected---it \textit{never} goes both ways. If instead the photons are directed into a Mach-Zehnder interferometer, students then observe an interference pattern, suggesting that each photon must somehow take \textit{both} paths in the interferometer (in apparent contradiction of the first experiment). Finally, the interference pattern is observed to disappear if the photons are ``tagged'' to distinguish which path they take, only to mysteriously reappear if that path information is ``erased'' after emerging from the interferometer. In this talk, I will provide an overview of these experiments and the accompanying theory that students learn in this course.