The theoretical notion of a ‘quantum heat engine’ has been around for several decades. It was first introduced around sixty years ago by Scovil and Schulz-DuBois, two physicists at Bell Labs who drew an analogy between three-level masers and thermal machines.
![](https://scx1.b-cdn.net/csz/news/tmb/2019/theexperimen.jpg)
Source:
https://phys.org/news/2019-12-experimental-quantum.html