Nuclear spin entanglement distribution through 35 km of deployed fiber. Credit: C. M. Knaut et al.
Physicists from Harvard University have developed and successfully demonstrated the capabilities of the first quantum internet via optical fiber. The quantum internet sends information by superimposing photons in different quantum states and could be used to ensure “hacker-proof” information transfer.
The work, published in Nature, employed a 22-mile loop of existing telecommunication fiber throughout the Boston area to connect two quantum memory nodes located within Harvard's Laboratory for Integrated Science and Engineering. The 22-mile loop represents the longest fiber distance ever achieved between quantum memory nodes.
While quantum networks are incredibly secure, copying arbitrary quantum information is impossible, and transporting that information long distances is hard to achieve. By employing a silicon-vacancy center in each node, physicists were able to overcome this challenge by boosting signal loss using traditional methods. Nodes employing silicon vacancy centers can catch, store, and entangle quantum information all while correcting for signal loss.
"Since the light is already entangled with the first node, it can transfer this entanglement to the second node," said first author Can Knaut. "We call this photon-mediated entanglement."
Over the last few years, the researchers have leased optical fiber from a local provider in Boston, fitting their network on top of existing fiber to demonstrate the possibility of creating a quantum network with similar network lines.
"Showing that quantum network nodes can be entangled in the real-world environment of a very busy urban area, is an important step towards practical networking between quantum computers," said Mikhail Lukin, Professor in the Department of Physics.
Currently, the researchers are expanding their experiment to include additional nodes and networking protocols.