  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.
