There are several ways to try to theoretical model such system. We need to consider the effect of “quantum fluctuations” and therefore the Master equation description is only valid when transport is assisted by thermally activated processes. Instead, when tunneling broadening is considered we need to switch to another approximation that takes into account such fluctuations. For this purpose we can implement the following schemes

• A modified Master equation scheme in which we consider cotunneling processes, or coherent transport. Here, we know that we do not need to consider a minimal model of four states to get a finite drag current. A model of three states is suffice.

• The P(E) theory implemented within the Master equation formalism. This theory takes into account the fact that quantum fluctuations due to the environment can occur and they can assist the carrier to be transported across the nanostructure.

• Utilizing a Green function scheme with “interacting” Green functions for the dots. This theory would need to be built from the scratch.