KNOXVILLE, Tenn. (WATE) — Could the internet of the future as fast as the speed of light? That’s what a team at Oak Ridge National Laboratory created on a smaller scale at the Department of Energy site. The team, including members from Stanford and Purdue universities, developed and demonstrated a fully functional quantum local area network.

The QLAN used entangled photons passing through an optical fiber to enable real-time adjustments to information shared with geographically isolated systems.

Currently, the internet sends information in binary code by bursts of light through optical fibers, copper wire, or microwaves. A quantum internet would use photons, the smallest possible particle of light, to carry large volumes of data across immense distances faster than the speed of light.

“We’re trying to lay a foundation upon which we can build a quantum internet by understanding critical functions, such as entanglement distribution bandwidth,” said Nicholas Peters, the Quantum Information Science group leader at ORNL. “Our goal is to develop the fundamental tools and building blocks we need to demonstrate quantum networking applications so that they can be deployed in real networks to realize quantum advantages.”

The Bob laboratory houses a GPS antenna and the second node in the new network. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

The researchers linked together three remote nodes, known as “Alice,” “Bob” and “Charlie” — names commonly used for fictional characters who can communicate through quantum transmissions — located in three different research laboratories in three separate buildings on ORNL’s campus. From the laboratory containing Alice and the photon source, the photons distributed entangled photons to Bob and Charlie through ORNL’s existing fiber-optic infrastructure. 

Quantum networks are incompatible with amplifiers and other classical signal boosting resources. With this potential drawback in mind, the team incorporated flexible grid bandwidth provisioning, which uses wavelength-selective switches to allocate and reallocate quantum resources to network users without disconnecting the QLAN.

This technique provides a type of built-in fault tolerance through which network operators can respond to an unanticipated event, such as a broken fiber, by rerouting traffic to other areas without disrupting the network’s speed or compromising security protocols.
“Because the demand in a network might change over time or with different configurations, you don’t want to have a system with fixed wavelength channels that always assigns particular users the same portions,” said Joseph Lukens, a Wigner Fellow and research scientist at ORNL as well as the team’s electrical engineering expert. “Instead, you want the flexibility to provide more or less bandwidth to users on the network according to their needs.”

Compared with their typical classical counterparts, quantum networks need the timing of each node’s activity to be much more closely synchronized. To meet this requirement, the researchers relied on GPS. Using a GPS antenna located in Bob’s laboratory, the team shared the signal with each node to ensure that the GPS-based clocks were synchronized within a few nanoseconds.
Having obtained precise timestamps for the arrival of entangled photons captured by photon detectors, the team sent these measurements from the QLAN to a classical network, where they compiled high-quality data from all three laboratories.

The third and final node used in the experiment is located in the Charlie laboratory. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

The team anticipates that small upgrades to the QLAN, including adding more nodes and nesting wavelength-selective switches together, would form quantum versions of interconnected networks — the literal definition of the internet.
“The internet is a large network made up of many smaller networks,” said Muneer Alshowkan, a postdoctoral research associate at ORNL. “The next big step toward the development of a quantum internet is to connect the QLAN to other quantum networks.”

Additional applications include improving detection techniques, such as those used to seek evidence of dark matter, the invisible substance thought to be the universe’s predominant source of matter.
“Imagine building networks of quantum sensors with the ability to see fundamental high-energy physics effects,” Peters said. “By developing this technology, we aim to lower the sensitivity needed to measure those phenomena to assist in the ongoing search for dark matter and other efforts to better understand the universe.”
The researchers are already planning their next experiment, which will focus on implementing even more advanced timing synchronization methods and further improve the QLAN’s quality of service.

The team’s results are published in PRX Quantum.

An earlier version of this story contained incorrect information about the speed of the quantum local area network. The speed could only be as fast as the speed of light. We apologize for the error.