Quantum loop entangles photons over 52-mile fiber network

Technology News | February 20, 2020

By Rich Pell

IoT Wireless Communications Authentication & Encryption Interconnect & cables Memory & Data Storage Materials & processes Test and Measurement Optoelectronics

The researchers entangled photons – i.e., where photons share their states even though they’re in different locations enabling a potential transfer of information – across a 52-mile network in the Chicago suburbs. The loop, say the scientists, is among the longest land-based quantum networks in the nation and seen as a foundational building block in the development of a quantum internet – potentially a highly secure and far-reaching network of quantum computers and other quantum devices.

A quantum internet, say the researchers, could significantly improve the security of communications and support dramatic advances in computing and sensing. Such quantum technology could revolutionize national and financial security, patient privacy, drug discovery, and the design and manufacturing of new materials, while increasing our scientific understanding of the universe.

“This is an important step forward in harnessing entanglement and building a network to help form the basis of future quantum communication systems,” says Argonne senior scientist and UChicago professor David Awschalom. “We are excited by these initial demonstrations of distributing entanglement outside of a laboratory, as well as having a flexible communications platform that allows us to identify the challenges of translating quantum phenomena to the real world.”

Originating at Argonne and winding circuitously in a pair of 26-mile loops through several of Chicago’s western suburbs, the network, say the scientists, taps the unique properties of quantum mechanics to eventually “teleport” information virtually instantaneously across a distance. In addition, the information should be extremely difficult to hack — quantum states change when observed, so the presence of an outside listener would actually change the signal itself.

Argonne plans to scale the network by developing a two-way quantum link network with Fermi National Accelerator Laboratory. Such a link could help to lay the foundation for a national laboratory-led, cross-country quantum internet.

To date, quantum systems, which are extremely sensitive to interference, have been mainly tested in clean, controlled lab environments. This experiment instead runs through an existing underground network of optical fiber, built decades ago for conventional telecommunications.

“In the real world, the fiber cables are expanding and contracting as the temperature changes,” says Tian Zhong, Argonne scientist in the Nanoscience and Technology division and assistant professor of Molecular Engineering at UChicago. “There is also vibration and noise from the environment such as local traffics. These are all factors that can affect the quantum signal transmission, and that we can only find out by performing an experiment of this magnitude under real-world operating conditions.”

In achieving this milestone, say the scientists, they worked closely with companies in the emerging quantum industry. In partnership with Qubitekk, a new company developing quantum technologies, the team created entangled photon pairs and distributed them across two 26-mile fiber loops. The returning photon pairs were detected, and their correlation was verified with a high signal-to-noise ratio.

On a related note, the White House on Feb. 11 announced funding and a strategic vision for quantum networks in the United States. The plan envisions companies and national laboratories over the next five years working together to demonstrate the foundational science and key technologies to enable quantum networks, and over the next 20 years, quantum internet links that enable new capabilities not possible with classical technology.

Argonne National Laboratory