They are playing with statistics and montecarlo stuff. Somehow it would work too in rocket science, you just have to try a lot of designs and after a while a significant portion of them will reach the moon, but they deemed the convergence speed to low, or the cost to high, I don't remember wich.
edit: a more serious answer is in the article, entanglement or not the algorithm naturally converge towards the solution. And they did not even check with convergence speed (I think the quantic version is meant to be faster) but they checked on some statistical criterion that is different in the quantic version and the plain version.