  We experimentally investigate a discrete time quantum walk in a system of
coupled fiber loops and observe typical phenomena known from the wave
propagation in periodic structures as ballistic spreading or an oscillation
between two internal quantum states similar to Zitterbewegung (trembling
motion). If a position-dependent phase gradient is applied we find localization
and Bloch oscillations of the field for moderate as well as Landau-Zener
tunneling for strong phase gradients.
