The development of quantum walks in the context of quantum computation, as generalizations of classical random walk techniques, led rapidly to several new quantum algorithms. These all follow unitary quantum evolution, apart from the final measurement. There are two types of quantum walks, that is, the discrete-time (or coined) and the continuous-time quantum walks. In this paper we discuss the discrete and continuous-times quantum walk, respectively. Most of the our argument are based on continuous-time quantum walk in terms of spectral distribution.
