  We investigate the Unruh quantum Otto heat engine with level degeneracy. An
effectively two level system, where the ground state is non-degenerate and the
excited state is $n$-fold degenerate, is acting as the working substance, and
the vacuum of massless free scalar field serves as a thermal bath via the Unruh
effect. We calculate the heat and work at each step of the Unruh quantum Otto
cycle and study the features of the heat engine. The efficiency of the heat
engine depends only on the excited energy values of the two level system, not
on its level degeneracy. However, the degeneracy acts as a kind of
thermodynamic resource and helps us to extract more work than in the
non-degenerate case. The extractable work has a finite upper bound,
corresponding to $n\rightarrow \infty$.

Quantum Physics;General Relativity and Quantum Cosmology;High Energy Physics - Theory