  In the quest for signatures of coherent transport we consider exciton
trapping in the continuous-time quantum walk framework. The survival
probability displays different decay domains, related to distinct regions of
the spectrum of the Hamiltonian. For linear systems and at intermediate times
the decay obeys a power-law, in contrast to the corresponding exponential decay
found in incoherent continuous-time random walk situations. To differentiate
between the coherent and incoherent mechanisms, we present an experimental
protocol based on a frozen Rydberg gas structured by optical dipole traps.
