Pre-service physics teachers’ use of photon concept in the context of single-photon double-slit experiment

Research in physics education has revealed that students often have incomplete and incoherent ways to use the concept of photon. Most researchers in science education recommend photons to be taken in a realistic sense as existing entities of quantum objects. Furthermore, in science education literature it is often claimed that realistic stance to photons also is preferred by physicists. Taken that photons in quantum theory of light invariably refer to quantized degrees of the freedom of an electromagnetic field it is questionable how one should introduce photons as entities without inadvertently supporting naïve particle-realism about photons, a well-known situation in introductory teaching of quantum theory of light. Fewer researchers suggest that photons should be understood as photon states, quantized degrees of freedom of electromagnetic field, as in contemporary quantum optics and quantum theory of light. Here, by using a questionnaire (a Likert-scale survey), we explore pre-service physics teachers’ preferences to use expressions that can be associated with either quanton or photon state views about photons in context of single-photon double-slit experiment. The questionnaire is administered in two stages (in the beginning and after a teaching sequence) during a pre-service physics teachers’ course addressing quantum optics and technology. Based on the analysis of the responses, we find that at the beginning of the course, the responses are scattered but in the final survey, clusters corresponding to use of photon state-based expressions become more consistent.