IQUIST-NRIK collaboration to build the first quantum network with open-air links

Quantum computers and secure quantum networks are operating in limited fashions, bringing us to the cusp of a quantum era. Before we can realize their full potential, though, we must increase their size and complexity. The most advanced systems today use around 100 processing units, or qubits, but the powerful applications quantum computers promise will require millions (or even billions) of qubits.

One approach is a distributed quantum network: recognizing that large, single-location quantum computers are difficult to construct, qubits are spread across multiple nodes and exchange quantum information via devices called quantum repeaters.

The National Research Institute of Korea (NRIK) began funding a five-year initiative on August 1 to construct a distributed quantum network connecting nodes separated by 20 kilometers. It will also be the first “hybrid” network connecting nodes using both optical fibers and open-air links to mobile platforms like drones. University of Illinois Urbana-Champaign researcher Paul Kwiat will play an integral role in its development.

Kwiat, the Bardeen Professor of Physics and Electrical Engineering and researcher in UIUC’s Illinois Quantum Information Science and Technology Center (IQUIST), has known the principal investigator, Hee Su Park of the Korean Research Institute of Standards and Science (KRISS), since Park was a visiting scientist in his research group 10 years ago. They collaborated on a technique that has led to what is now the world’s most efficient single-photon source.

“In the current project, we will extend [our] methods even further and combine them with other quantum technologies we have been developing in my lab,” Kwiat said, and the results will enable quantum-repeater enabled networks with unprecedented efficiency.

Kwiat’s research group is also responsible for developing free-space quantum links between mobile platforms. Their experiments have shown that quantum information can be relayed over the open air between two flying drones like targeted radio signals.

The UIUC group will pursue several other new levels of quantum state distribution, quantum teleportation, and entanglement swapping: the central technologies crucial to the network’s realization. This includes efficient sources of entangled photon pairs such as quantum dots—artificial nanoparticles that mimic natural atoms. They fundamentally cannot produce more than a single pair of photons at a time, so quantum dot sources would greatly reduce network noise.

Kwiat said his and his collaborators’ innovations “should enable the world’s most advanced reconfigurable multi-node quantum network.”

In addition to Kwiat’s UIUC group and Park’s KRISS group, researchers from the Korea Institute of Science and Technology and Chung-Ang University are participating in the NRIK initiative titled “Development of Core Technologies for Entanglement-Based Multi-Party Hybrid Quantum Networks.”

The award was for 4.736 billion won, of which UIUC received 1.421 billion ($1.1 million) to allow students and scientists to travel between the four groups in order to visit and perform work in each other’s laboratories.