  Quantum information is based on the apparent contradictions between classical
logic and quantum coherence described by Kochen-Specker contextuality.
Surprisingly, this contradiction can be demonstrated in a comparatively simple
three-path interferometer, where it is impossible to trace the path of a single
photon through five consecutive stages of the interferometer. Here, I discuss
the paradoxical aspects of single photon interferences revealed by the
three-path interferometer and point out the essential role of dynamics in
quantum information.
