  Quantum systems exist at finite temperatures and are likely to be disordered
to some level. Since applications of quantum information often rely on
entanglement, we require methods which allow entanglement measures to be
calculated in the presence of disorder at non-zero temperatures. We demonstrate
how the disorder averaged concurrence can be calculated using thermal many-body
perturbation theory. Our technique can also be applied to other entanglement
measures. To illustrate, we find the disorder averaged concurrence of an XX
spin chain. We find that concurrence can be increased by disorder in some
parameter regimes.
