Background:
The study investigated the use of Quantum Physics Conceptual Survey (QPCS) in probing student understanding of quantum physics.

Material and methods:
Altogether 103 Finnish university students responded to QPCS. The mean scores of the student responses were calculated and the test was evaluated using common five indices: Item difficulty index, Item discrimination index, Item point biserial index, Kuder-Richardson Formula 21, and Ferguson’s delta.

Results:
The results show that QPCS is not well suitable for probing Finnish university students’ understanding of basic ideas of quantum physics in its current form. Based on the calculated indices, QPCS was too difficult for the participating students as an introductory-level test. The discrimination ability of QPCS was also vague. There were numerous individual test items, which were both too difficult and poor discriminators. Particularly, the items of theme Waves and Particles seemed to be problematic because they required understanding of the Standard interpretation of quantum mechanics, which is not discussed in the Finnish upper secondary curriculum or in basic physics studies in the university.

Conclusions:
It seems that the QPCS may have potential as an instrument to probe Finnish students’ understanding of quantum physics but only after some careful modifications.