@article {edselc.2-52.0-8491257105020141101,
	title = {Universal features in the efficiency at maximal work of hot quantum Otto engines},
	journal = {EPL},
	volume = {108},
	year = {2014},
	pages = {40001},
	abstract = {Classically, external power optimization over the coupling times of a heat engine to its baths leads to universal features in the efficiency. Here we study internal work optimization over the energy levels of a multilevel quantum Otto engine, and find similar universal features. It is shown that in the ultra-hot regime the efficiency is determined solely by the energy level optimization constraint, and is independent of the engine{\textquoteright}s details. Constraints on the energy levels naturally appear due to physical limitations or design goals. For some constraints the results significantly differ from the classical universality.},
	issn = {12864854},
	url = {http://iopscience.iop.org/article/10.1209/0295-5075/108/40001},
	author = {Uzdin, R. and Kosloff, R.}
}
