Quantum Cellular Automata Models for General Dirac Equation
  The goal of this study is to provide an exact unitary quantum cellular automata that, under discrete time steps, converges towards the Generalized Dirac Equation (GDE) in the continuum limit. The evolutionary rules for such a single particle walk are discussed in this paper, and it is shown that this quantum celluar automata will maintain similar properties to the GDE. 
Xingyou Song
quant-ph