Quantum internet closer as physicists stretch spooky link between atoms

Science | AAAS | 2/13/2020 | Staff
blackyblacky (Posted by) Level 3
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Physicists in China have stretched a mysterious quantum connection between particles, called entanglement, to dozens of kilometers using standard optical fibers, smashing the previous record. The advance marks a long step toward a fully quantum mechanical internet—although such a network is still years away.

The achievement springs not from one particular breakthrough, but from the careful implementation of multiple techniques, says David Awschalom, a physicist at the University of Chicago. “I’m very impressed that they’ve integrated these various technologies into a full system,” he says. “It’s a beautiful piece of work.”

States - Objects - Example - Clockwise - Counterclockwise

Entanglement links the strange states of tiny quantum mechanical objects. For example, a top can spin either clockwise or counterclockwise, but an atom can spin both ways at once—at least until it is measured and that two-way state collapses one way or the other. Two atoms can be entangled so that each is in an uncertain two-way state, but their spins are definitely correlated, say, in opposite directions. So if physicists measure the first atom and find it spinning clockwise, they know instantly the other one must be spinning counterclockwise, no matter how far away it is.

Entanglement would be key to a fully quantum internet that would let quantum computers of the future communicate with one another and be immune to hacking. If hackers messed with communication, they would spoil the entanglement, revealing their presence. Various companies already sell systems that send messages in quantum states of light that are largely unhackable. But to use such links, the information must still be decoded at each network node, which is potentially vulnerable. In a quantum internet, any node could be entangled with any other, so messages between them couldn’t be decoded at intermediate nodes.

Developers - Entanglement - Distances - Researchers - Entanglement

But developers must first stretch entanglement over greater distances. Previously, researchers had demonstrated entanglement over 1.3 kilometers of optical...
(Excerpt) Read more at: Science | AAAS
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