It is possible to build a quantum engine that is driven by constantly changing the fundamental quantum properties of the particles it contains. Such devices could one day be used to power other quantum technologies.
All known particles can be classified as either fermions or bosons, and which category they fall into determines how they behave in large groups. Arthur Videla Researchers at the University of Kaiserslautern-Landau in Germany have developed a way to build engines using collections of atoms, by making them behave first as bosons, then as fermions, and then as bosons again.
The differences between these two types of particles are most pronounced in the quantum realm, especially at extremely low temperatures. So researchers built an engine from hundreds of thousands of lithium atoms cooled to temperatures well below absolute zero.
Under these conditions, the researchers used carefully tuned magnetic fields to force the lithium atoms to behave like groups of fermions, or to form molecular-like pairs, and then Made them act like a group.
The researchers started with a collection of paired atoms, like bosons. They first compressed them and then converted them into collections of fermions, increasing their collective energy.
Widera and his colleagues then expanded the atoms. They also tweaked the magnetic field to reform the atomic pairs, returning them to a bosonic state and lowering their overall energy. In this way, the researchers used atoms like the “working fluid” in a traditional engine, extracting work through repeated cycles of compressing and expanding the fluid.
Currently, ultracold atomic engines are about 25% efficient, but Widera said scientists could tweak them to be even more efficient. “We don’t want to drive the next Mercedes-Benz with a quantum engine, but we have shown for the first time that it is possible to drive an engine with purely quantum forms of energy,” he says.
Sebastian Deffner The University of Maryland, Baltimore County researchers point out that the difference between fermions and bosons is a quantum property not available in conventional machines, which sets the new engine apart from existing devices. This difference makes it important to consider whether it becomes a true quantum resource and can be used in a technologically advantageous way, he says.
As quantum engines become more practical, they could eventually be used to charge other devices, such as quantum batteries, he says. Gabriele de Chiara At Queen’s University Belfast, UK. It could also be used “in reverse” to cool down devices like quantum computers, which are known to have more errors as they warm up, he says.
- quantum mechanics/
- quantum physics