"World's smallest ball game" tosses single atoms between light traps
Scientists in South Korea have created what they call "the world’s smallest ball game," throwing individual atoms between two optical traps. The research could eventually make for more adaptable and dynamic quantum computers.
The ability to use lasers to trap and manipulate individual atoms, particles and even live bacteria was a Nobel Prize-winning breakthrough. The radiation pressure of light can be strong enough to move or hold microscale objects, making for optical tweezers, traps and maybe even tractor beams.
For the new study, researchers at the Korea Advanced Institute of Science and Technology (KAIST) developed a way to throw an atom from one trap to another. As usual with this kind of setup, the team started by cooling a cloud of rubidium atoms down to almost absolute zero, then trapped them in a grid of lasers tuned to a wavelength of 800 nanometers.
To throw them around, the team accelerates one optical trap, then switches it off so the atom goes flying. To catch it, another trap is then turned on to slow it down until it stops. In tests, the scientists threw atoms across distances of 4.2 micrometers at speeds of up to 65 cm (26 in) per second.
“The freely flying atoms move from one place to the other without being held by or interacting with the optical trap,” said Jaewook Ahn, lead author of the study. “In other words, the atom is thrown and caught between the two optical traps much like the ball travels between the pitcher and a catcher in a baseball game.”
Intriguingly, the team showed that atoms could be thrown through other stationary optical traps without interfering with them or interacting with other atoms along the way. This means it could be an effective technique for moving atoms around an array without having to reset the whole thing.
“We often encountered arrangement errors that rendered an array defective,” said Ahn. “We wanted to find an efficient way to fix a defective array without having to move a large number of atoms, because that could result in even more defects.”
The technique could also be used to make more dynamic quantum computers, allowing qubits of information to be moved in relation to each other. Before then though, the team plans to continue working to improve the success rate for the creation of free-flying atoms up from around 94%.
The research was published in the journal Optica.