Physicists investigate fundamental limits of quantum engines

Quantum engines are known to operate differently than—and in some cases, outperform—their classical counterparts. However, previous research on the performance of quantum engines may be overestimating their advantages. In a new study, physicists have developed an improved method to compute the efficiency of quantum engines. They show that the ultimate efficiency of quantum systems is subject to tighter fundamental limits than those imposed by the second law of thermodynamics, which governs the efficiency of classical systems.

Physicists Obinna Abah and Eric Lutz at the Friedrich-Alexander University Erlangen-Nürnberg in Germany have published a paper on the energy-efficient quantum machines in a recent issue of EPL. Abah is currently a Royal Commission for the Exhibition of 1851 research fellow at Queen's University in Belfast, UK.

The performance of any kind of engine—quantum or classical—is largely determined by its energy efficiency (the ratio of energy output to energy input) and its power (the rate of energy output in a given time). Conventional thermodynamics imposes a tradeoff between an engine's efficiency and its power—meaning when you increase one, the other decreases. For quantum engines, however, it's possible to increase both the efficiency and the power at the same time. This means that, with the proper methods, quantum engines can potentially produce more energy output from a given amount of energy input, and do so at a faster rate than before the improvement.