We report on a multi-year, multi-institution study to investigate students' reasoning about energy in the context of quantum tunnelling. We use ungraded surveys, graded examination questions, individual clinical interviews and multiple-choice exams to build a picture of the types of responses that students typically give. We find that two descriptions of tunnelling through a square barrier are particularly common. Students often state that tunnelling particles lose energy while tunnelling.

During individual clinical interviews, the interaction between researcher and interviewee leads to a specific set of data that can later be interpreted from several viewpoints. In this paper, we describe three analyses of a student's reasoning. First, we describe her "physics reasoning" in terms of the physical situation she describes and the "difficulties" she has in reasoning about the interview question. Second, we describe some "reasoning resources" that she uses. Finally, we describe "epistemological resources" that may influence her reasoning about quantum physics.

Members of the University of Maine Physics Education Research Laboratory are studying student understanding of the phenomenon of quantum tunneling through a potential barrier, a standard topic in most introductory quantum physics courses. When a series of interviews revealed that many students believe energy is lost in the tunneling process, a survey was designed to investigate the prevalence of the energy-loss idea. This survey was administered to populations of physics majors at the sophomore and senior levels.