Physicists Built an Engine That Runs On a Single Atom

On a microscopic level, heat is simply atoms vibrating off one another, in constant motion.

Heat engines, like steam turbines, use systems relying on thermodynamics to convert the energy from heat into mechanical work. The Industrial Revolution would never have happened if not for the power of heat engines, and we're still using them today. You probably know its most recognizable forms: the automobile engine and the jet engine.

But scientists are challenging the stereotypical notion of the heat engine as a large, metal behemoth. In fact, researchers at the Institute of Physics of Johannes Gutenberg University Mainz and Friedrich-Alexander-Universität Erlangen-Nürnberg recently pushed the powerhouse to its farthest limits when they successfully created a heat engine that operates using a single atom.

The team of researchers, who published their findings in the latest edition of the journal Science, captured a single electrically-charged calcium atom in a quadrupole ion trap—also known as a "Paul trap." This specific type of ion trap uses two positive and two negative electrodes to trap a charged particle, by both pushing it toward the center and simultaneously pulling it outward.

Using electrically-generated noise, the group of physicists was then able to heat the particle, thus subjecting it to a thermodynamic cycle, according to the study. This caused the particle to vibrate back and forth within the trap, much like a regular heat engine. To cool the particle down, researchers used a laser beam.

In order to find out what type of power their miniature heat engine would produce at a scaled-up level, the physicists performed rounds of thermodynamic tests to determine that their "single particle engine can generate power of 10-22 watts and operates at 0.3 percent efficiency," according to findings. This means that at a much larger scale, its output would be identical to that of a car engine.

"By reversing the cycle, we could even use the device as a single atom refrigerator and employ it to cool nano systems coupled to it," said co-author Johannes Roßnagel.

In addition to creating something pretty cool and innovative in their field, the study's authors hope their findings will also strengthen burgeoning research into quantum thermodynamics. According to the study, researchers are interested the ways that quantum heat engines could be used to increase the engine's power. If results are stable, this could open the door for the invention of completely new modes of power.