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Can students apply the concept of "which-path" information learned in the context of Mach Zehnder Interferometer to the double-slit experiment?

The ability to use concepts learned in one context to solve problems in a different context (i.e., transfer of learning) is a hallmark of expertise in physics. The majority of the studies on transfer of learning in physics have focused on introductory students. However, compared to advanced students, introductory students have significantly less prior relevant knowledge and skills which may be crucial for promoting effective transfer. Here, we examine upper-level undergraduate and graduate students' ability to transfer their learning about the concept of "which-path" information and its relation to whether or not interference is observed from the context of the Mach Zehnder Interferometer (MZI) to a new context of the double-slit experiment (DSE). Students worked through a tutorial on the MZI in which they learned to use the concept of "which-path" information to reason about interference of single photons when polarizers with various orientations are placed in one or both paths of the MZI. After working on the MZI tutorial, students were asked similar questions in the isomorphic context of the DSE before any instruction about the DSE and we examined the extent to which transfer of learning about "which-path" information occurred from the MZI to the DSE context. We find evidence suggesting that positive transfer of learning from the MZI to the DSE occurred despite the lack of an instructional intervention designed to help students recognize the similarity between the two contexts. The effectiveness of the MZI tutorial in promoting positive transfer of learning from one context to another in quantum mechanics sheds light on the expertise of the advanced physics students. Instructors of advanced physics courses can take advantage of the findings presented here which shows the difference between introductory and advanced students' ability to transfer from one context to another.