  A single-piston quantum engine based on a harmonic oscillator acting as the
working fluid is proposed. Using the fact that the interaction between the
piston and the oscillator depends on the extent of the oscillator wavefunction,
one can control this interaction by modifying the oscillator temperature. By
retracting the piston when the interaction is weak (hot oscillator) and
returning it to the original position when the coupling is strong (cold
oscillator), useful work can be performed assuming the interaction is
attractive. The cycle of the engine is simulated numerically using two
different powering protocols: bath and measurement. Using the collision model
for the baths, the engine is shown to reach a steady state with positive work
output.
