  We have studied the performance of a measurement-based quantum Otto engine
(QOE) in a working system of two spins coupled by Heisenberg anisotropic
interaction. A non-selective quantum measurement fuels the engine. We have
calculated thermodynamic quantities of the cycle in terms of the transition
probabilities between the instantaneous energy eigenstates, and also between
the instantaneous energy eigenstates and the basis states of the measurement,
when the unitary stages of the cycle operate for a finite time $\tau$. The
efficiency attains a large value in the limit of $\tau \rightarrow 0$ and then
gradually reaches the adiabatic value in a long time limit $\tau \rightarrow
\infty$. For finite values of $\tau$ and for anisotropic interaction, an
oscillatory behaviour of the efficiency of the engine is observed. This
oscillation can be interpreted in terms of interference between the relevant
transition amplitudes in the unitary stages of the engine cycle. Therefore, for
a suitable choice of timing of the unitary processes in the short time regime,
the engine can have a higher work output and less heat absorption, such that it
works more efficiently than a quasi-static engine. In the case of an always-on
heat bath, in a very short time the bath has a negligible effect on its
performance.
