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For the First Time, Scientists Detect a Moving Photon Multiple Times Without Destroying It

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A view of one of the research team's two vacuum chambers.RR

Researchers in Germany have detected a single photon twice without destroying it as it traveled along an optical fiber.

Credit: Max Planck Institute of Quantum Optics

The act of detecting a photon typically destroys it. Now scientists have for the first time nondestructively detected a single traveling photon not just once, but multiple times. Such research could make future quantum communications networks and quantum computers faster and more robust, they say.

Quantum communications networks are in principle virtually unhackable, and quantum computers theoretically can be more powerful than any supercomputer. These devices often use photons for communications or computations.

Detecting photons typically requires absorbing them. However, in some applications, a single photon may carry valuable information, such as data needed for a quantum computation. In such cases, scientists would like to read out the photon's data but also keep track of the photon as it travels in order to make sure it reaches its final destination successfully.

"No detector is ever 100% efficient—there's always a chance may slip through not detected," says study senior author Stephan Welte, a quantum physicist at the Max Planck Institute for Quantum Optics in Garching, Germany. With more than one detector linked together in a series, "you enhance the chance of detection."

From IEEE Spectrum
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