Undergraduate physics experiments that concurrently elucidate single-photon counting, second-order and fourth-order interference.

Undergraduate students enrolled in courses in Modern Physics and Optics are introduced to formulations of optical interference that cement classical interpretations based upon one-photon  (second order) interference. Therefore, to grasp quantum mechanical interpretations that govern two-photon (fourth order) interference, these students need to expand their understanding and un-learn foundational ideas. Furthermore, because of the requisite statistical analysis, students rarely envision interference with a countable number of photons. Quantum optics, a field that until recently was esoteric, has become quite mainstream. Accordingly, it is critically important that students gain exposure to these dual interpretations early in their careers.

 

In order to investigate and present these concepts concurrently, we have implemented hardware for: (1) single photon counting using coherent and chaotic sources (with software to model the Poisson/exponential distributions); (2) electrooptic phase modulated laser-feedback interferometry; (3) Mach-Zehnder interferometry and (4) Hanbury Brown and Twiss (HBT) interference. These approaches enable users to directly compare results and apply concepts that govern the observed fringe visibility, coherence time and Hong-Ou-Mandel interference effects.