  While strong system-bath coupling produces rich and interesting phenomena,
applications to quantum thermal engines have been so far pointing mainly at
detrimental effects. The delicate trade-off between efficiency loss due to
strong coupling and power increase due to faster equilibration, while
acknowledged, remained largely unexplored owing to the challenge of assessing
precisely the equilibration time. Here, we overcome this obstacle by exploiting
exact numerical simulations based on the hierarchical equations of motion
(HEOM) formalism. We show that a quantum Otto cycle can perform better at
strong (but not ultrastrong) coupling in that the product of the efficiency
times the output power is maximized in this regime. In particular, we show that
strong coupling allows one to obtain engines with larger efficiency than their
weakly coupled counterparts, while sharing the same output power. Conversely,
one can design strongly coupled engines with larger power than their weakly
coupled counterparts, while sharing the same efficiency. Overall, our results
provide situations where strong coupling can directly enhance the performance
of thermodynamic operations, re-enforcing the importance of studying quantum
thermal engines beyond standard configurations.
