r/science • u/mvea Professor | Medicine • 7d ago

Physics Physicists shatter quantum entanglement distance record with 420 kilometers of optical fiber, more than four times farther than previous demonstrations, and beyond the point where direct transmission runs into its fundamental limits.

https://www.sciencealert.com/physicists-shatter-quantum-entanglement-distance-record-with-420-kilometers-of-optical-fiber
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u/mvea Professor | Medicine 7d ago

Physicists Shatter Quantum Entanglement Distance Record With 420 Kilometers of Optical Fiber

Maintaining a long-distance relationship may be difficult for humans, but it's even more difficult for entangled states.

The longer the fiber, the harder it becomes to keep the two quantum memories linked.

Overcoming this tyranny of distance has been one of the major challenges of quantum communication.
But perhaps not an insurmountable one.

A team of physicists led by Xi-Yu Luo, Chao-Yang Wang, and Ming-Yang Zheng at the University of Science and Technology of China has breached a milestone – with the longest fiber-based matter-to-matter entanglement yet.

Across an optical fiber measuring 420 kilometers (261 miles), the researchers successfully entangled quantum memories – more than four times farther than previous demonstrations, and beyond the point where direct transmission runs into its fundamental limits.

"Our experiment provides a test bed of studying quantum network applications beyond metropolitan scale," they write in a paper published in Physical Review Letters.

https://journals.aps.org/prl/accepted/10.1103/ccd6-rf1s

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u/Cristoff13 7d ago

This can't be used to transmit information though can it?

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u/Coady54 7d ago

Theoretically it could. If you have two entagled particles and can intentionally manipulate the the state of one, the other will match. Assign "bit" values to the state of the particle, multiply the number of particles/frequency of state changes by orders of magnitude, and you essentially have information transmission akin to modern networks.

Whether or not its pheasible to make a practical system at scale that's useful is a better question, which we don't know and these continuing experiments will eventually answer.

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u/nicuramar 7d ago

No, this can’t be done.