Scientists stopped light for entire minute

“Freezing” the light could be major breakthrough in quantum memory storage and information processing. 

One minute is not long time. We all can agree on that. But stopping something that is able to move at 300 million meters per second is simply amazing. This successful project was finished at Technische Universität Darmstadt in Germany, where scientist were able  to stop the light for record-breaking one minute.

The reason why scientists decided to freeze the light is to make sure that it still has its quantum coherence properties, thus making it possible to build light-based quantum memory.

Stopping light used already known methods. Credit: Katrin Binner

Stopped the light was not easy. Light is electromagnetic radiation. In one minute, the light is capable of travel distance as long as 18 million kilometers (11 million miles), or 20 round trips from the Earth to the Moon.

Light indeed can be slowed down. In fact, this was not the first time that light was successfully kept still for 16 seconds before by using cold atoms.

Thomas Halfmann working on freezing the light. Credit: Katrin Binner

For this particular experiment, Thomas Halfmann and his team changed light coherence into atomic coherence. It was done by using a quantum interference effect that makes opaque medium (this case a crystal) transparent over a narrow range of light spectra.  This process is called electromagnetically induced transparency (EIT). They shot laser right through crystal, which was in this case a source of light and this sent its atoms into a quantum superposition of two states. After that a second beam switched off the first laser, hence the transparency. Thus the researchers collapsed the superposition and trapped the second beam inside. 

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Energy-level scheme for EIT experiments, credit: Heinze et al.

Physicist Hugues de Riedmatten in an associated Physic Review article said: “The result outperforms earlier demonstrations in atomic gases by about six orders of magnitude and offers exciting possibilities of long-storage-time quantum memories that are spatially multiplexed, i.e., can store different quantum bits as different pixels.” 

As with many projects and researches, there are plans for the future. The scientists will try to use different substances to increase the time that they can freeze the light and explore the information stored inside even further.

source: journals.aps.org

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