  We show that coupled two level systems like qubits studied in quantum
information can be used as a thermodynamic machine. At least three qubits or
spins are necessary and arranged in a chain. The system is interfaced between
two split baths and the working spin in the middle is externally driven. The
machine performs Carnot-type cycles and is able to work as heat pump or engine
depending on the temperature difference of the baths $\Delta T$ and the energy
differences in the spin system $\Delta E$. It can be shown that the efficiency
is a function of $\Delta T$ and $\Delta E$.
