Transport of quantum excitations via local and nonlocal fluctuations

In quantum systems, one usually seeks to minimize dephasing noise and disorder. The efficiency of transport in a quantum system is usually degraded by the presence of noise and disorder. However, it has been shown that the combination of the two can lead to significantly more efficiency than each by itself. Here, we consider how the addition of nonlocal noise, in the form of incoherent hopping, affects the transport efficiency. We show that incoherent hopping introduces additional local extrema in the efficiency function and investigate the crossover from a quantum random walk to a classical random walk.