Record-Setting Quantum Entanglement Connects Two Atoms Across 20 Miles

Researchers from two Germany universities 'have demonstrated quantum entanglement of two atoms separated by 33 km (20.5 miles) of fiber optics," reports New Atlas. Besides being a new distance record, "The team says this is an important step on the way to realizing a practical quantum internet."In their experiments, the team entangled two rubidium atoms kept in optical traps in two different buildings on the Ludwig-Maximilians-University Munich campus. They were separated by 700 m (2,297 ft) of fiber optics, which was extended out to 33 km with extra spools of cable. Each atom was excited with a laser pulse, which causes it to emit a photon that's quantum entangled with the atom. The photons are then sent down the fiber optic cables to meet at a receiving station in the middle. There, the photons undergo a joint measurement, which entangles them - and because they're each already entangled with their own atom, the two atoms become entangled with each other as well. While photons have been entangled over great distances before, this study marks a new distance record for entangling two atoms, which could function as "quantum memory" nodes, over fiber optics.

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