  We propose a four level quantum heat engine in Otto cycle with a working
substance of two spins subject to an external magnetic field and coupled to
each other by a one-axis twisting spin squeezing nonlinear interaction. We
calculate the positive work and the efficiency of the engine for different
parameter regimes. In particular, we investigate the effects of quantum
correlations at the end of the two isochoric processes of the Otto cycle, as
measured by the entanglement of formation and quantum discord, on the work
extraction and efficiency. The regimes where the quantum correlations could
enhance the efficiency and work extraction are characterized.
