Quantum Internet Unlocked as Qubits Teleported Over Fiber Links

Quantum Internet Takes Shape as Scientists Transmit Qubits Over Long Distances

As companies like Google, IBM and others race to build powerful quantum computers, a parallel effort is underway to construct the "quantum internet" that will allow these machines to communicate securely over long distances. In a major milestone, scientists from three different countries have independently demonstrated the ability to transmit delicate quantum bits, or qubits, through fiber optic cables spanning over 20 miles.

At the Delft University of Technology in the Netherlands, a team led by Ronald Hanson encoded qubits into electrons of nitrogen atoms in diamond crystals. They were able to transmit the quantum states from the university to a lab 25 miles away in The Hague by sending photons through an existing fiber optic cable.

Halfway around the world in China, researchers at the University of Science and Technology used clouds of rubidium atoms to store qubits. By encoding the quantum information into photons, they established entanglement between three labs separated by over 6 miles.

And at Harvard University, Mikhail Lukin's group took a different approach, using silicon atoms in diamond devices. They demonstrated entanglement of two nodes over 22 miles by sending a single photon through a looped fiber cable to successively interact with the silicon atoms at each location.

"Since the light is already entangled with the first node, it can transfer this entanglement to the second node," explained Can Knaut, a Harvard graduate student. "We call this photon-mediated entanglement."

While still limited to relatively short distances, the work proves that the backbone of the future quantum internet can leverage the existing global fiber optic infrastructure. This would allow separate quantum computers to be linked, or distribute cryptographic keys with perfect security.

Pan Jian-Wei of the University of Science and Technology told Nature he expects entanglement over 600 miles to be possible by 2030 based on the current trajectory. A quantum network of that scale could connect huge optical telescope arrays into one seamless virtual observatory.

The quantum internet revolution is taking its first steps out of the lab. Though challenges remain, harnessing quantum phenomena over global distances now seems an achievable goal in the coming decade.