Throwing and catching atoms one by one with optical tweezers

KAIST Research Team, Using Laser Beams
Enables Development of More Powerful Quantum Computers

Domestic researchers have succeeded in developing a technology that can execute atomic movement and placement more efficiently as a fundamental element of quantum computers. Using a 'optical tweezer' with a laser beam, atoms can be caught, thrown, and caught one by one, enabling the development of quantum computers with more powerful performance than the conventional method of transporting atoms individually.

The Korea Advanced Institute of Science and Technology (KAIST) announced on the 27th that Professor Jae-Wook Ahn's research team in the Department of Physics developed a technology to throw and catch rubidium atoms one by one using a laser beam.

Schematic diagram of the technique of throwing and catching a single atom using optical tweezers
The optical tweezer on the left accelerates and throws the atom, and the optical tweezer on the right catches and stops it. Image source: KAIST

The technology of moving and arranging atoms, which is a basic principle of quantum computers, is very important in Rydberg quantum computing research. To place atoms at desired positions, a highly focused laser beam called an optical tweezer is generally used to catch and transport atoms one by one. The problem has been that the quantum information of atoms is highly likely to change during this process.

The research team developed a method to throw and catch atoms by minimizing the contact time between the optical tweezer and the atoms, preventing changes in quantum information. They utilized the characteristic that rubidium atoms, cooled to a temperature 40 millionths of an absolute zero below zero Kelvin, move very sensitively along the focus of the optical tweezer due to the electromagnetic force exerted by light. By accelerating the laser of the optical tweezer to give an optical kick to the atoms, they sent the atoms to the target point and then caught and stopped the flying atoms with another optical tweezer. The flight speed of the atoms is 65 cm/s, and the moving distance is up to 4.2 micrometers.

Compared to the existing technology of catching and moving atoms with optical tweezers, this method eliminates the need to calculate the optical tweezer’s movement path for atom relocation and makes it easier to fix defects in the atomic array. As a result, it is effective in generating and maintaining large numbers of atomic arrays. When additionally throwing and catching atoms carrying quantum information (flying atom qubits), it is possible to study new and more powerful quantum computing methods that assume structural changes in the quantum array.

Professor Jae-Wook Ahn said, “This technology will be used to develop larger and more powerful Rydberg quantum computers. In Rydberg quantum computers, atoms store quantum information and are arranged to perform quantum computing by interacting with adjacent atoms through electromagnetic forces. If errors occur and atoms need to be replaced or moved, throwing atoms to quickly reconfigure the system could be an effective method.”

This research was published in the international academic journal Optica in the March issue, volume 10, number 3. The paper is titled 'Optical tweezers throw and catch single atoms.'