Neutral atoms and charged ions can be cooled down to extremely low temperatures (i.e., to microkelvins, 1 millionth of a degree above absolute zero) using laser techniques. At these low temperatures, the particles have often been found to behave in accordance with the laws of quantum mechanics.
![](https://scx1.b-cdn.net/csz/news/tmb/2019/1-quantum.jpg)
Source:
https://phys.org/news/2020-02-cooling-ion-quantum-regime.html