Scientists Create First Working Long-Distance Quantum Network Prototype

Brad Chacos

Powerful quantum computing and instantaneous long-distance quantum communication ( ala the Normandy's quantum entanglement communicator in Mass Effect) sound well and good, but in reality, that sort of technology will never blossom unless we figure out how to create working quantum networks first. Oh wait! We have. Yesterday, scientists from the Max Planck Institute of Quantum Optics in Germany announced that they've created the first quantum link between two atoms located far away from one another physically.

Two rubidium atoms were prepared in two different labs, with each atom stationed in an "optical cavity" between a pair of reflective mirrors stationed half a millimeter apart. Each atom acts as a quantum bit; when it sheds a photon, the polarization of the photon contains the qubit information (read: quantum state) of the originating atom.

The scientists coaxed an atom into emitting a photon using a laser, then blasted the photon into an optical fiber that carried it to the corresponding setup in the second lab. When the atom in the second lab absorbed the photon, it took on the same quantum state as the original atom. Bam! Information transferred and stored.

The optical cavity is the secret sauce; atoms and photons are really, really small and would normally be way more likely to miss each other completely than smack into one another and become one. The reflective mirror walls of the optical cavity keep the blasted photon pinballing back and forth until it slams into the atom.

Even more exciting, the scientists were then able to entangle the two atoms on a quantum level despite the distance between them. When two atoms are entangled, any changes made to one occur in the second one, as well -- instantaneously and regardless of the distance between them. Or, as Einstein called it, "spooky action at a distance."

The research team envisions eventually creating a quantum network with the technology, using a series of similar optical cavity setups as "quantum repeaters" in a node-type structure. The full report is behind a paywall at Nature , but Scientific Computing has a great, detailed synopsis of the findings up for free.

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