While the basic procedure for producing a quantum random walk can be outwardly similar to its classical counterpart, the dynamics of a quantum walk are completely different since they are affected by interference and entanglement. We present a discrete-time quantum walk based on the entanglement between the momentum of ultra-cold rubidium atoms (the walk space) and two internal atomic states (the “coin” degree of freedom). Our scheme is highly flexible and can provide a broad platform for the realization of a wide range of applications such as quantum search algorithms, the observation of topological phases, and the realization of walks with higher dimensionality. We demonstrate the distinctive features of a quantum walk, contrasting them to the behavior of a classical walk. By manipulating either the walk or coin operator we show how the walk dynamics can be steered or even reversed, with immediate applications in matter-wave interferometry.
Host: Nir Navon