Photons Seen Without Being Destroyed For First Time Ever

Scientists have used a single atom trapped in an optical resonator to detect the presence of a reflected photon
without destroying that packet of light. | MPQ, Quantum Dynamics Division

If you want to see a packet of light called a photon, you have to destroy it. Any device that picks up on the presence of light has to absorb its energy, and with it, the photons. At least, that was what scientists thought until now.

At the Max Planck Institute of Quantum Optics in Germany, researchers found a way to detect single, visible-light photons without "touching" them and losing the photons themselves.

The work, detailed in the Nov. 14 issue of the journal Science Express, has important implications for quantum computing devices and communications. In an ordinary computer the presence of electrons — current — encodes the bits in logic circuits. Being able to keep photons around while still detecting them means photons could be used in a similar way. [Wacky Physics: The Coolest Little Particles in Nature]

"We could build gates between photons and atoms," Stephan Ritter, physicist and co-author of the study, told LiveScience. In any computer gates are the building blocks of logic circuits, which control functions such as AND, OR and NOT in a computer's brain.

Others have detected photons without destroying them, the most notable being Serge Haroche at the Collège de France in Paris, who won a Nobel Prize in 2012 for the achievement. However, he detected photons comprising microwave wavelengths of light. The Max Planck team detected visible-light photons, which are more useful for quantum communications.

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