  Heat engines extract work by running cyclically between two heat reservoirs.
When the two reservoirs are thermal and at different temperatures, the maximum
efficiency of the engine is given by the Carnot limit. Here we consider a
quantum Otto cycle for a time-dependent harmonic oscillator coupled to an
engineered squeezed thermal reservoir. We show that the efficiency at maximum
power increases with the degree of squeezing, exponentially approaching unity
for large squeezing parameters $r$. Furthermore, we propose an experimental
scheme to implement such a system by using a single trapped ion in a linear
Paul trap with special geometry and coupled to engineered reservoirs. Our
analytical investigations are supported with Monte Carlo simulations that
demonstrate the feasibility of our proposal. For realistic trap parameters, an
increase of up to a factor of four is reached, largely exceeding the classical
limit.
