Parallelism represents an essential aspect of human mind/brain activities. One can recognize some common features between psychological parallelism and the characteristic parallel structures that arise in quantum theory and in quantum computation. The article is devoted to a discussion of the following questions: 1) a comparison between classical probabilistic Turing machines and quantum Turing machines; 2) possible applications of the quantum computational semantics to cognitive problems; 3) parallelism in music.

Quantum computation and quantum computational logics are intrinsically connected with some puzzling epistemic problems. In the framework of a quantum computational approach to epistemic logic we investigate the following question: is it possible to i