Researchers Demonstrate A Single Atom Light Switch

Researchers Develop a Single Atom Light Switch
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In a newly published study, researchers from the Vienna University of Technology demonstrate highly efficient switching of optical signals between two optical fibers controlled by a single atom.

The Quantum Light Switch: It can occupy both possible states at the same time.

With just a single atom, light can be switched between two fiber optic cables at the Vienna University of Technology. Such a switch enables quantum phenomena to be used for information and communication technology.

Fiber optic cables are turned in to a quantum lab: scientists are trying to build optical switches at the smallest possible scale in order to manipulate light. At the Vienna University of Technology, this can now be done using a single atom. Conventional glass fiber cables, which are used for internet data transfer, can be interconnected by tiny quantum systems.

Light in a Bottle

Professor Arno Rauschenbeutel and his team at the Vienna University of Technology capture light in so-called “bottle resonators”. At the surface of these bulgy glass objects, light runs in circles. If such a resonator is brought into the vicinity of a glass fiber which is carrying light, the two systems couple and light can cross over from the glass fiber into the bottle resonator.

“When the circumference of the resonator matches the wavelength of the light, we can make one hundred percent of the light from the glass fiber go into the bottle resonator – and from there it can move on into a second glass fiber”, explains Arno Rauschenbeutel.

Light in a bottle: An optical fiber with a captured beam of light.

A Rubidium Atom as a Light Switch

This system, consisting of the incoming fiber, the resonator and the outgoing fiber, is extremely sensitive: “When we take a single Rubidium atom and bring it into contact with the resonator, the behavior of the system can change dramatically”, says Rauschenbeutel. If the light is in resonance with the atom, it is even possible to keep all the light in the original glass fiber, and none of it transfers to the bottle resonator and the outgoing glass fiber. The atom thus acts as a switch which redirects light one or the other fiber.

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