Quantum walks with a one-dimensional coin

Mar 24, 2016
8 pages
Published in:
  • Phys.Rev.A 93 (2016) 6, 062334
e-Print:

Citations per year

201520182021202420251034
Abstract: (arXiv)
Quantum walks (QWs) describe particles evolving coherently on a lattice. The internal degree of freedom corresponds to a Hilbert space, called coin system. We consider QWs on Cayley graphs of some group GG. In the literature, investigations concerning infinite GG have been focused on graphs corresponding to G=ZdG=\mathbb{Z}^d with coin system of dimension 2, whereas for one-dimensional coin (so called scalar QWs) only the case of finite GG has been studied. Here we prove that the evolution of a scalar QW with GG infinite Abelian is trivial, providing a thorough classification of this kind of walks. Then we consider the infinite dihedral group DD_\infty, that is the unique non-Abelian group GG containing a subgroup HZH\cong\mathbb{Z} with two cosets. We characterize the class of QWs on the Cayley graphs of DD_\infty and, via a coarse-graining technique, we show that it coincides with the class of spinorial walks on Z\mathbb{Z} which satisfies parity symmetry. This class of QWs includes the Weyl and the Dirac QWs. Remarkably, there exist also spinorial walks that are not coarse-graining of a scalar QW, such as the Hadamard walk.
Note:
  • 8 pages, 4 figures
  • 03.67.Ac
  • 02.20.-a