Piotr Garbaczewski and Witold Karwowski Impenetrable Barriers and Canonical Quantization (64K, Revtex4, Latex) ABSTRACT. We address an apparent conflict between the traditional canonical quantization framework of quantum theory and spatially restricted quantum dynamics when the translation invariance of an otherwise free quantum system is broken by boundary conditions. By considering the example of a particle in an infinite well, we analyze spectral problems for related confined and global observables. In particular, we show how we can interpret various operators related to trapped particles by not ignoring the rest of the real line that is never occupied by a particle.