  Recent findings suggest that processes such as the electronic energy transfer
through the photosynthetic antenna display quantal features, aspects known from
the dynamics of charge carriers along polymer backbones. Hence, in modeling
energy transfer one has to leave the classical, master-equation-type formalism
and advance towards an increasingly quantum-mechanical picture, while still
retaining a local description of the complex network of molecules involved in
the transport, say through a tight-binding approach.
  Interestingly, the continuous time random walk (CTRW) picture, widely
employed in describing transport in random environments, can be mathematically
reformulated to yield a quantum-mechanical Hamiltonian of tight-binding type;
the procedure uses the mathematical analogies between time-evolution operators
in statistical and in quantum mechanics: The result are continuous-time quantum
walks (CTQWs). However, beyond these formal analogies, CTRWs and CTQWs display
vastly different physical properties. In particular, here we focus on trapping
processes on a ring and show, both analytically and numerically, that distinct
configurations of traps (ranging from periodical to random) yield strongly
different behaviours for the quantal mean survival probability, while
classically (under ordered conditions) we always find an exponential decay at
long times.
