  Based on quantum thermodynamic processes, we make a quantum-mechanical (QM)
extension of the typical heat engine cycles, such as the Carnot, Brayton, Otto,
and Diesel cycles, etc. The temperature is not included in these QM engine
cycles, as lies in the fact that the concept of energy is well-defined in
quantum mechanics, temperature \emph{a priori} is not. These QM engine cycles
are implemented by an ideal or interacting system with an arbitrary number of
particles confined in an arbitrary power-law trap. As a result, a relation
between the quantum adiabatic exponent and trap exponent is found. The
efficiency of a given QM engine cycle is similar to that of its classical
counterpart, thereby identifying the universality of the efficiency.
