Developing a quantum way of thinking is a core and challenging
task for physics students. The concept of quantum state, whose physical meaning is connected to the formal structure of the theory, plays an important role in the construction of a quantum perspective and in student difficulties elicited by research. A questionnaire and interview protocol were devised to explore student understanding of the state concept in connection to the properties of its formal representations and to quantum behavior. Results of a calibration of research instruments performed on
6 physics students from different universities are here presented.
