Quantum computing has long promised unprecedented computational power, but a formidable obstacle has stood in its way: the challenge of connecting quantum computers over long distances without losing the delicate quantum information. Traditional fiber optic links are severely limited in the distance they can support quantum communications, restricting practical quantum networks to just a few kilometers. This bottleneck has kept the dream of a functional quantum internet out of reach — until now.
A transformative breakthrough from the University of Chicago’s Pritzker School of Molecular Engineering may change the landscape of quantum networking forever. Led by Assistant Professor Tian Zhong, the research team has engineered a system that could extend the quantum communication range up to a staggering 2,000 kilometers — almost 200 times the previous record. This paradigm-shifting development could finally enable a global quantum internet, connecting distant quantum processors across entire continents.
At the heart of this innovation lies an improvement in quantum coherence times — the duration for which atoms maintain their fragile quantum states when entangled over fiber optic channels. Quantum entanglement is the key to linking spatially separated quantum computers, but decoherence has traditionally limited the effective communication distance. Zhong’s team has achieved a quantum coherence time exceeding 10 milliseconds in erbium atoms embedded within specially crafted quantum materials, a leap from the mere 0.1 milliseconds typical of prior efforts.
This ten-millisecond coherence marks a critical threshold for quantum communication, theoretically enabling quantum links up to 2,000 kilometers — equivalent to connecting quantum devices between Chicago and distant cities like Salt Lake City. In some instances, coherence times extended even further, reaching an impressive 24 milliseconds, which, if realized in practical networks, could allow connections spanning over 4,000 kilometers, from Chicago to Colombia.
Intriguingly, this leap forward did not come from inventing new quantum materials but rather from a revolutionary change in how these materials were manufactured. Traditionally, rare-earth doped crystals — essential for quantum light-matter interfaces — were grown using the Czochralski method, which involves melting raw materials above 2,000 degrees Celsius and cooling them slowly into crystals. Afterward, physical sculpting is used to fashion components from these crystals, a cumbersome and imprecise process.
Instead, the University of Chicago team employed molecular-beam epitaxy (MBE), a technique more akin to 3D printing at the atomic scale. MBE deposits material layer-by-layer, allowing precise control over crystal growth and composition from the ground up. This bottom-up approach produces ultrahigh-purity materials with atomic-level precision, vastly improving the quantum coherence properties of embedded erbium ions critical for long-lived entanglement.
MBE’s application to rare-earth doped crystals is unprecedented in the quantum information domain. Working alongside materials synthesis expert Assistant Professor Shuolong Yang, Zhong’s group adapted MBE to tailor these crystals specifically for quantum networking. The high-quality epitaxial films they created admit a robust spin-photon interface operating at telecom wavelengths, perfectly suited for long-distance fiber transmission compatible with existing infrastructure.
Esteemed experts in photonics and quantum technologies have praised this innovative approach for its scalability and groundbreaking nature. Professor Hugues de Riedmatten of the Institute of Photonic Sciences, a recognized leader in quantum networking, emphasizes that this work demonstrates how precise nanofabrication methods can realize single rare-earth ion qubits with exceptional optical and spin coherence, paving the way for scalable, fiber-compatible quantum devices.
Although the theory and materials science breakthroughs are profound, Zhong and his team acknowledge that practical validation lies ahead. Their next phase involves rigorous laboratory experiments to confirm whether the extended coherence times translate into long-distance quantum communication. This will include linking two qubits housed inside separate dilution refrigerators using spooled fiber lengths simulating up to 1,000 kilometers.
Currently, Zhong’s lab is constructing a third dilution refrigerator to establish a local quantum network capable of simulating future extended quantum internet architectures. These developments represent incremental but essential milestones toward a functional quantum communication network capable of spanning urban centers, states, and ultimately the globe.
The potential implications are immense. A robust quantum internet would revolutionize secure communications by enabling unhackable quantum encryption, advance distributed quantum computing by linking remote quantum processors, and open avenues for quantum-enhanced sensing and metrology over vast distances.
This research fundamentally redefines the material science foundations of quantum networking by combining state-of-the-art nanofabrication with the physics of rare-earth ions. Its success promises to blur geographical boundaries currently limiting quantum technologies, fostering a new era where quantum computers communicate seamlessly from city to city and country to country.
Published in the prestigious journal Nature Communications on November 6, 2025, this work titled “Dual epitaxial telecom spin-photon interfaces with long-lived coherence” marks a significant milestone toward the quantum internet era. Its broad technological ramifications underscore the importance of interdisciplinary collaboration between quantum physics, materials science, and engineering.
In conclusion, the University of Chicago team’s innovative molecular-beam epitaxy fabrication method has unlocked an extraordinary increase in quantum coherence times in telecom-band erbium ions, theoretically extending the quantum communication range by two orders of magnitude. As laboratory tests advance, the dream of connecting quantum computers across continents inches closer to reality, heralding a revolution in secure communication and computational power unparalleled by classical technologies.
Subject of Research: Quantum computing; quantum coherence; rare-earth doped materials; quantum networking; molecular-beam epitaxy.
Article Title: Dual epitaxial telecom spin-photon interfaces with long-lived coherence
News Publication Date: November 6, 2025
Web References:
References:
Gupta et al., “Dual epitaxial telecom spin-photon interfaces with long-lived coherence,” Nature Communications, November 6, 2025, DOI: 10.1038/s41467-025-64780-6
Image Credits: University of Chicago Pritzker School of Molecular Engineering / Jason Smith
Keywords: Quantum computing, Quantum information, Molecular-beam epitaxy, Quantum coherence, Telecommunication wavelength, Rare-earth doped crystals, Quantum internet, Spin-photon interface
