Contextual particle propagation in a three-path interferometer

Abstract

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.