A team of physicists at the Australian National University (ANU) have managed to stop light using an ultra-cold cloud of rubidium atoms. The experiment, reported in the Nature Physics, could be used to build a quantum logic gate – an important building block in the development of light-based quantum computer.

“Optical quantum computing is still a long way off, but our successful experiment to stop light gets us further along the road,” said Jesse Everett, lead author of the study in a news release. “Quantum computers based on light – photons – could connect easily with communication technology such as optic fibres and had potential applications in fields such as medicine, defence, telecommunications and financial services.”

Light travels at a speed of around 300,000 kilometers per second. However, it’s still possible to travel faster – not by making yourself travel faster, but by making the light slower. In this experiment, the team used rubidium atoms which were modified so that when they were shined with infrared lasers, they constantly emitted and then re-captured the light – giving a cloud of stationary light.

“While it was not the first time physicists had stopped light, the system they had developed meant they could show the light was stationary,” Ben Buchler, senior author on the paper, said in a statement at ABC News. “With this experiment we have the best proof that the light is actually stationary because we have taken photos of the atoms from the side that show they are in the right pattern to support the stationary light.”

In the image below, what you see as the red glow in the center is a cloud of atoms used to make the stationary light.

Physicists Stop Light Using Cloud Of Rubidium Atoms

What physicists actually did here is that they held the light’s information in one place, leaving an impression on surrounding atoms as light is absorbed. By doing so, they could make it serve as storage system, where light information can be stored and retrieved by setting it in motion again as another light wave, notes a post on Cosmos.

“Our method allows us to manipulate the interaction of light and atoms with great precision,” explained Buchler.

Geoff Campbell, who is a co-researcher, said photons mostly passed by each other at the speed of light without any interactions, while atoms interacted with each other readily. Forcing a crowd of photons in an ultra-cold cloud of rubidium atoms would give more opportunities for photons to interact.

“We’re working towards a single photon changing the phase of a second photon. We could use that process to make a quantum logic gate, the building block of a quantum computer,” he added.

[Image via ABC News]

Reference: Dynamical observations of self-stabilizing stationary lightNature Physics