University of Chicago Breakthrough Enables Quantum Computer Connections 200 Times Farther
- MM24 News Desk
- 3 hours ago
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University of Chicago researchers have developed a novel crystal fabrication method that extends quantum computer connection distances from just a few kilometers to a theoretical 2,000 kilometers—a 200-fold increase. Led by Professor Tian Zhong, this breakthrough in extending quantum coherence times from 0.1 milliseconds to 24 milliseconds could finally make a global-scale quantum internet achievable, potentially linking quantum computers from Chicago to Salt Lake City with unprecedented stability.
The formidable challenge of connecting quantum computers over long distances may have just met its solution, according to groundbreaking research published today in Nature Communications. Professor Tian Zhong and his team at the University of Chicago Pritzker School of Molecular Engineering (UChicago PME) have developed an innovative approach that dramatically extends how far quantum computers can communicate through fiber cables.
Previously, quantum computers could only connect across distances of a few kilometers—not even enough to link the University of Chicago's South Side campus to downtown Chicago's Willis Tower. The new technique theoretically extends that range to 2,000 km (1,243 miles), enough to connect Chicago to Salt Lake City, reported Nature Communications.
"For the first time, the technology for building a global-scale quantum internet is within reach," said Professor Tian Zhong, who recently received the prestigious Sturge Prize for this pioneering work. His enthusiasm reflects what could be a watershed moment for quantum networking.
The secret lies in dramatically extending quantum coherence times—the duration that entangled atoms maintain their quantum state. Traditional methods achieved coherence times of just 0.1 milliseconds, severely limiting connection distances. Zhong's team has boosted this critical metric to longer than 10 milliseconds, with one demonstration reaching an impressive 24 milliseconds—enough to theoretically connect quantum computers across 4,000 km, the distance from Chicago to Ocaña, Colombia.
The breakthrough came not from discovering new materials but from building existing materials differently. Rather than using the conventional Czochralski method—which involves melting ingredients at temperatures above 2,000 degrees Celsius and slowly cooling them—the team employed molecular-beam epitaxy (MBE), a precise layer-by-layer assembly technique.
"The traditional way of making this material is by essentially a melting pot," Zhong explained to Nature Communications. "You throw in the right ratio of ingredients and then melt everything. It goes above 2,000 degrees Celsius and is slowly cooled down to form a material crystal."
In contrast, MBE builds crystals atom by atom, similar to 3D printing rather than sculpting. "We start with nothing and then assemble this device atom by atom," Zhong said. "The quality or purity of this material is so high that the quantum coherence properties of these atoms become superb."
The innovation emerged from collaboration with UChicago PME materials expert Professor Shuolong Yang, who helped adapt MBE for creating rare-earth doped crystals containing erbium atoms. These crystals form the foundation for creating the quantum entanglement necessary for long-distance connections.
International experts are taking notice of the significance of this advancement. Professor Dr. Hugues de Riedmatten from the Institute of Photonic Sciences, a world leader in quantum networking who was not involved in the research, called the approach "highly innovative."
"The approach demonstrated in this paper is highly innovative," de Riedmatten stated. "It shows that a bottom-up, well-controlled nanofabrication approach can lead to the realization of single rare-earth ion qubits with excellent optical and spin coherence properties, leading to a long-lived spin photon interface with emission at telecom wavelength, all in a fiber-compatible device architecture. This is a significant advance that offers an interesting scalable avenue for the production of many networkable qubits in a controlled fashion."
The research team is now preparing to test whether these extended coherence times actually enable practical long-distance quantum connections. Their next step involves creating a laboratory-scale network using multiple dilution refrigerators connected through 1,000 kilometers of spooled fiber cable.
"Before we actually deploy fiber from, let's say, Chicago to New York, we're going to test it just within my lab," Zhong explained. "We're now building the third fridge in my lab. When it's all together, that will form a local network, and we will first do experiments locally in my lab to simulate what a future long-distance network will look like."
This practical testing phase represents the crucial next step toward realizing the dream of a global quantum internet. The ability to connect quantum computers across continents could unlock unprecedented computational power, enable perfectly secure communications, and create networked quantum systems that solve problems currently beyond any single computer's capabilities.
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