Comment on ‘Full revivals in 2D quantum walks’
Randika Dodangodage, Asiri Nanayakkara · Physica Scripta · 2018
Abstract In the paper Štefaňák et al (2010 Phys. Scr. T 140 014035) have proved that for any four-state quantum walk, there cannot be cycles longer than two steps. Our investigations reveal that they have not used the most general form of characteristic polynomials in their proof. Consequently, the result is not generally valid and hence there can be quantum walks having cycles longer than two steps.