Quantum mechanics is included in many curricula across countries because of its cultural value and technological application. In the last decades, two-state approaches to quantum mechanics became popular because of the age of quantum computers. This article presents an experiment with 24 Hungarian high school students on teaching/learning quantum mechanics according to Dirac's approach to concepts and basic formalism developed in the context of light polarization. Tutorials, pre/post-tests, and oral interviews are the main monitoring tools used to collect data on the students’ learning path. From the qualitative and quantitative data analysis, learning progressions emerged in the phenomenology exploration and on the probabilistic nature of single quantum measurement. The students’ conceptions of quantum state are enriched, confirming the importance to focus educational approaches on fundamental topics. For one section of students, the complex relationship between quantum state and property remained problematic, but the students’ interpretations of a quantum state can be categorized. Two lines of reasoning emerged regarding the impossibility to attribute a trajectory to a quantum system, one more orthodox and one that seeks to avoid the probabilistic nature of the quantum world.

We present a new secondary school teaching method of quantum uncertainties of two-state systems. Intending to be a material teachable in schools, only two-state systems described by real numbers can be considered. An elementary argumentation based on school statistics leads to the identification of the uncertainty of a physical quantity in such systems with the standard deviation of two random variables. We provide a qualitative picture on the state-dependence of the uncertainty, leading to a pictorial representation in the form of four petals of a flower. When considering the product of uncertainty of two essentially different physical quantities we conclude that the general feature: “if the measurement of one of the quantities is certain, the other remains uncertain”, cannot be faithfully expressed by means of an inequality, the product has no lower bound different from zero. The application of techniques used by school materials for teaching quantum physics leads to an exact formula for the state-dependence of the uncertainty valid in any two-state system described by real numbers, in full harmony with the qualitative picture. We compare the two-state case with the celebrated Heisenberg position-momentum uncertainty relation and show that these are both specific facets, but only the Heisenberg relation can be expressed by an inequality. The latter hardly provides any hint on the uncertainties of physical quantities in two-state systems. We conclude that the two-state approach is worth teaching in schools also in relation to the uncertainty relation, even if the Heisenberg relation is not part of the curriculum.

In the 2019/20 school year I directed a teaching unit on quantum mechanics based on light polarization which enriched me with several experiences. Sometimes I faced problems because the obligatory Hungarian curriculum based on the wave nature of particles does not fit perfectly with the polarization approach of quantum physics. Nevertheless, I presented the polarization approach to my physics teacher colleagues too. Then I recognized some of the difficulties of Hungarian physics teachers in relation to this approach because they used to apply the wave approach. Thus, teacher training programmes should include the foundations of different approaches on equal footing, and in my opinion, teacher education should also respond to secondary school opportunities. In this article, I summarize the problems that may arise in applying the polarization approach in countries where wave formalism has a great tradition, like in Hungary. I also show why I personally prefer a 2-state approach in secondary school instead of the traditional wave formalism, and present what I have learned as a teacher. I highlight some of the requirements that arise when we intend to use polarization approach in physics teacher training programmes, and I make suggestions for teacher education too.

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