  We propose an experimental scheme to realize a nano heat engine with a single
ion. An Otto cycle may be implemented by confining the ion in a linear Paul
trap with tapered geometry and coupling it to engineered laser reservoirs. The
quantum efficiency at maximum power is analytically determined in various
regimes. Moreover, Monte Carlo simulations of the engine are performed that
demonstrate its feasibility and its ability to operate at maximum efficiency of
30% under realistic conditions.
