Physicists in China have forged a mysterious quantum connection between particles, called entanglement, over dozens of kilometers of standard optical fiber, setting a new 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.”

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.

Read more at Science magazine.

Image: Physicists used a special technique to help photons travel further down standard optical fibers. HENRIK500/ISTOCK