Effect of an introductory quantum physics course using experiments with heralded photons on preuniversity students’ conceptions about quantum physics

We conducted a quasiexperimental study in order to investigate the effect of a teaching concept on quantum physics based on coincidence and correlation experiments with heralded photons on preuniversity students’ conceptions of quantum physics (experimental group, $N=150$). We compare the results with the traditional curriculum’s effect (control group, $N=130$) at German secondary schools using a questionnaire to assess students’ conceptions of quantum physics adapted from the literature. The results show that students introduced to quantum physics using the quantum optics concept acquire conceptions of quantum physics that are significantly less influenced by classical mechanistic and deterministic conceptions than those of the control group. In more detail, correlation and principal component analysis results indicate that the conceptions acquired by experimental group students are more consistent than those of the control group students.

Figure 1

Core curriculum on quantum physics for secondary school teaching as revealed by Staderman et al. [31].

Figure 2

Schematic setup of the experiment by Grangier et al. [18]. The experiment is based on the principle of heralded photons. If a nonlinear crystal, e.g., beta-barium borate (BBO), is irradiated with intense light from a diode laser, a quantum electrodynamic process called parametric down-conversion sets in as a reaction of this crystal to the incident light [52]. Parametric down-conversion leads to the symmetrical emission of photon pairs due to the conservation of momentum. Two detectors A and B are placed symmetrically facing the crystal. Simultaneous detection events, called coincident events, at the two detectors A and B indicate these photon pairs with high probability. A click at one detector is therefore considered a necessary prerequisite for a single photon at the second detector, or in other words: if detector B clicks simultaneously with A, then B heralds a single photon at A. This can then be experimented with.

Figure 3

Interactive screen experiment on the behavior of single photons at the beam splitter to make quantum random tangible [51].

Figure 4

Screenshot from an explanatory video: to teach students the functioning of single photon detectors at an appropriate level, we have developed an analogy to the formation and departure of snow avalanches [53]. Step by step, the video guides students through the correspondences of our analogy. In this way, technical terms such as dark count event or dead time become accessible to students. We consider the basic knowledge of such terms to be a necessary prerequisite to understanding experiments with heralded photons.

Figure 5

Interactive screen experiment on single-photon interference [51].

Figure 6

We find a stronger increase of the mean conception index for quantum objects’ properties and behavior from pre- to postsurvey in the experimental group than in the control group.

Figure 7

Distribution of the post-test values of the conception index for the scale quantum objects’ properties and behavior in CG and EG (cf. Table 2).

Figure 8

Students’ transitions between high (HC), medium (MC), and low (LC) conception index groups from pre- to post-test based on the students’ results on the quantum objects’ properties and behavior scale. It is shown which number of students from each of the pretest groups HC, MC, and LC change to which group at the post-test point in time. For both survey time points, it is also indicated how many students are assigned to the three groups in total, for both EG and CG.

Figure 9

We find a stronger increase of the mean conception index for the probability interpretation of quantum physics from pre- to postsurvey in the experimental group than in the control group.

Figure 10

Distribution of the post-test values of the conception index for the scale probability interpretation of quantum physics in CG and EG (cf. Table 3).

Figure 11

Students’ transitions between high HC, MC, and LC from pre- to post-test based on the students’ results on the quantum physics’ probability interpretation scale. It is shown how many students from each of the pretest groups HC, MC, and LC change to which group at the post-test point in time. For both survey time points, it is also indicates how many students are assigned to the three groups in total, both for EG and CG.

Figure 12

Diverging stacked bar chart visualizing the distribution of student ratings on all items of the scale on the quantum objects’ properties and behavior (cf. Table 2).

Figure 13

Diverging stacked bar chart visualizing the distribution of student ratings on all items of the scale on the probability interpretation of quantum physics (cf. Table 3).