  We study a quantum system composed of three interacting qubits, each coupled
to a different thermal reservoir. We show how to engineer it in order to build
a quantum device that is analogous to an electronic bipolar transistor. We
outline how the interaction among the qubits plays a crucial role for the
appearance of the effect, also linking it to the characteristics of system-bath
interactions that govern the decoherence and dissipation mechanism of the
system. By comparing with previous proposals, the model considered here extends
the regime of parameters where the transistor effect shows up and its
robustness with respect to small variations of the coupling parameters.
Moreover, our model appears to be more realistic and directly connected in
terms of potential implementations to feasible setups in the domain of quantum
spin chains and molecular nanomagnets.
