Examining Student Understanding of the Mach-Zehnder Interferometer in Quantum Mechanics Classroom

In quantum mechanics instruction, it is essential to establish connections between the abstract quantum concepts learned in lecture and actual, physical experiments. This study investigates how advanced undergraduate physics students in a quantum mechanics classroom reason about quantum optical experiments, such as the Mach-Zehnder interferometer which demonstrates the role of superposition and interference in measurement outcomes. Analysis of their responses highlights both the strategies students employed and the conceptual challenges they encountered in relating formal quantum mechanical calculations to the physical behavior of the apparatus. Students examined this quantum optical setup through two mathematical tools, one through an operator mechanics-based approach using second quantization and a second through a simplified Feynman path integral approach. This talk presents our results from analyzing student interviews, where students were asked to determine the probability of detection at one of the interferometer's output detectors under two conditions: when the optical paths have equal lengths and when a path difference is introduced.