Quantum mechanics is responsible for examining the behavior of the universe at the smallest scale: atoms and subatomic particles that function in ways that traditional physics is unable to explain. To do this, the researchers try to make objects – ever larger – behave in a quantum way to answer all these unknowns.
In this experiment, a team of scientists from ETH Zurich managed to levitate a glass nanosphere using laser light and slow its movement to its lowest quantum mechanical state, “stopping time” in the sphere of 10 million 100-nanometer atoms. wide (1,000 times smaller than the thickness of a human hair), being able to observe this effect on a macroscopic scale – since in quantum physics, 10 million atoms is a fairly large object. This breakthrough could help us better understand quantum mechanics by bringing it closer to our size and using it in many more technologies.
“This is the first time that such a method has been used to control the quantum state of a macroscopic object in free space,” says Lukas Novotny, professor of photonics at ETH Zurich in Switzerland and co-author of the work published in the journal. Nature.
Moving the object closer to zero
To successfully carry out this experiment, the researchers used a vacuum vessel cooled to -269 degrees Celsius before using a feedback system to make a few more adjustments, as motion and energy must be immediately dialed in to achieve quantum states. Thus, the sphere was levitated in an optical trap, keeping it suspended in the air thanks to an optical trap that was placed in a vacuum container and cooled to a temperature of a few degrees above absolute zero as we have seen.
To slow the sphere further, the team used another laser and the light reflected from the sphere, creating an interference pattern that allowed the laser to be adjusted in such a way that the light pushing and pulling the sphere caused it to slow down. to its fundamental state.
“To clearly see the quantum effects, the nanosphere must be slowed down to its ground state of motion”, clarifies electrical engineer Felix Tebbenjohanns, leader of the study. “This means that we freeze the energy of motion of the sphere to a minimum close to the zero point motion of quantum mechanics.”
Although similar, though not the same, advancements had already been made in optical resonators, this method allows examination of the sphere in complete isolation once the interference laser is turned off, allowing the quantum wave in the sphere to expand freely. . The good thing about this approach is that it better protects the nanosphere against disturbances and means that the object can be seen in isolation after turning off the laser, although that will require a lot more research, of course.
For starters, managing to levitate such a large sphere in a cryogenic environment represents a significant leap onto the macroscopic scale where the line between the classical and the quantum can be studied.
“Along with the fact that the potential for optical trapping is highly controllable, our experimental platform offers a route to investigate quantum mechanics at macroscopic scales,” conclude the experts.
They could revolutionize our world. Better and better sensors would be crucial for ultra-accurate measurements.
Referencia: Quantum control of a nanoparticle optically levitated in cryogenic free space. Felix Tebbenjohanns et al. Nature volume 595, pages378–382 (2021). DOI: https://doi.org/10.1038/s41586-021-03617-w