Quantum networks hold enormous potential for groundbreaking advances in many areas of science and technology. Once this technology matures, it is expected to be an essential component of quantum computing. It could have the equivalent impact as the internet has had on digital communication.
The U.S. Department of Energy (DOE) has announced that three collaborative projects in quantum networking will receive $24 million for up to three years. The DOE's Argonne National Laboratory will be participating in two of the projects and leading one of them, InterQnet. Anticipated funding for InterQnet is $9 million over three years.
Quantum networks would lead to breakthroughs in quantum computing by linking multiple quantum computers to greatly boost computational power. This technology could also advance precision measurements based on quantum principles that would otherwise not be possible. And it could pave the way for new applications yet to be conceived.
Our results will serve as the bedrock for scaling up quantum networks to connect quantum devices around the nation.
Rajkumar Kettimuthu, Computer Scientist
The InterQnet project will address multiple challenges with scaling up quantum networks from the current metropolitan scale to much longer distances and more complex architectures. To that end, Argonne is collaborating with DOE's Fermi National Accelerator Laboratory (Fermilab), Northwestern University, the University of Chicago and the University of Illinois Urbana-Champaign.
The quantum processes involved govern the behavior of elementary particles, such as photons, which are the fundamental constituents of light. The key process is called entanglement. Two entangled particles are interdependent even after they are separated over vast distances.
"What fascinates me about quantum networks is that they can transport information in a fundamentally new way," said Rajkumar Kettimuthu, a computer scientist at Argonne and principal investigator for InterQnet. "They allow you to communicate quantum information from one point to another in a network by leveraging quantum entanglement while also transmitting classical information; this is different from transmitting the quantum information over a communication medium, such as a fiber-optic cable, or free space."
He further explained that because entanglement-based quantum communication requires transmittal of classical information from source to destination, you cannot communicate quantum information faster than light.
"We have already demonstrated quantum communication with entangled photon pairs in a laboratory, between buildings at Argonne, and between Argonne and Fermilab," Kettimuthu said.
InterQnet will be showcasing quantum communication across five buildings on the Argonne campus with multiple distinct quantum platforms and an early-stage quantum repeater. Each platform will use a different type of quantum bit (qubit), the basic unit of information in quantum information. Unlike classical bits, which can only be either 0 or 1, a qubit can simultaneously represent a combination of both states. This characteristic is one reason quantum computers possess vastly superior computational capabilities for some applications.
Argonne researchers previously collaborated in the development of four types of qubits: electrons, ytterbium atoms, charged erbium atoms (ions) and microwave circuits. A significant milestone would be to demonstrate the Argonne quantum network connecting these distinct qubit platforms. One of them would serve as a quantum repeater, an essential network element to extend the communication distance.
"Our results will serve as the bedrock for scaling up quantum networks to connect quantum devices around the nation," Kettimuthu said. The team will complement practical experiments with computer simulations to determine the optimal architecture for a futuristic quantum network scalable to great distances.
This new project grew out of work done in various earlier and ongoing projects. These include several Argonne Laboratory Directed Research and Development projects; the Illinois Express Quantum Network (IEQNET) led by Fermilab; and Q-NEXT, a DOE Office of Science national quantum information science (QIS) center led by Argonne.
InterQnet will also leverage various existing QIS hardware and software elements already in place. These include the fiber-optics connection between Argonne and partner institutions and a quantum network simulator developed at Argonne.
Fermilab has been awarded DOE funding for a separate project, Advanced Quantum Network for Scientific Discovery. This Fermilab-led project will leverage the expertise and capabilities developed by IEQNET. The objective is to improve the transmission of information over quantum networks. Collaboration between the two national labs will continue as Argonne will also participate in the project along with other partners.
"Quantum networks are the foundation for distributed and scaled-up quantum computing, which has potential applications in banking, national security, energy delivery infrastructure, information security and many others," said Panagiotis Spentzouris, associate laboratory director for emerging technologies at Fermilab.