  We study the quantum correlations embedded in open quantum Rabi systems.
Specifically, we study how the quantum correlation depends on the coupling
strength, number of qubits, and reservoir temperatures. We numerically
calculate the quantum correlations of up to three qubits interacting with a
single field mode. We find that the embedded quantum correlations exhibit a
maximum for a given coupling strength, which depends inversely on the number of
subsystems and the reservoir temperature. We explore how this feature affects
the performance of a many-qubit Otto heat engine, finding numerical evidence of
a direct correspondence between the minimum of the extractable work and the
maximum of the embedded quantum correlations in the qubit-cavity bi-partition.
Furthermore, as we increase the number of qubits, the maximum extractable work
is reached at smaller values of the coupling strength. This work could help
design more sophisticated quantum heat engines that rely on many-body systems
with embedded correlations as working substances.
