## Quantum walks

A quantum walk is a quantum version of a classical random walk. The walk can take place on a line or on a more general structure, a graph. There are three different versions of quantum walks, coined walks and scattering walks, both of which are discrete-time walks, and continuous-time walks. Quantum walks have proven useful in search problems, where the task is to find a particular, marked vertex in a graph, and a quantum walk can find such a vertex with a quantum speedup.