Researchers Report Stable Quantum Links Over Kilometers of Noisy Fiber
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Researchers at the National Institute of Standards and Technology (NIST) and the University of Colorado, Boulder have achieved stable quantum links over kilometers of standard optical fiber, a critical advancement for building practical quantum networks.
The team successfully separated the signals needed for fiber stabilization, trillions of photons per second, from the single photons carrying quantum information, overcoming a significant technical hurdle. This demonstration combines highly stabilized fiber links, strong separation between the classical stabilization light and the quantum signal, and compatibility with high-bandwidth optical pulses, according to lead researcher Nick Nardelli from NIST. These stabilized links are envisioned as a foundation for emerging technologies like distributed quantum computing and secure communication protocols, bringing photonic quantum networking closer to real-world applications.
Fiber Stabilization Adapts Atomic Clock Techniques for Quantum Networks The innovation lies in applying fiber stabilization methods from optical atomic clocks, allowing for nanometer-level precision in controlling the optical path of light. This advancement addresses a significant challenge: separating the intense light used for stabilization from the single photons that carry delicate quantum information. The system works by briefly flooding the fiber with a bright reference laser to detect distortions, correcting them in real time before switching off to allow the quantum signal to pass through. This cycle, repeating thousands of times per second, ensures minimal disturbance to the quantum state. Experiments revealed that photons traveling 2 kilometers through the stabilized fiber remained over 99% indistinguishable at their destination, a crucial metric for maintaining quantum coherence. They also mitigated timing errors to less than 100 attoseconds, preventing phase scrambling of the quantum state. Nardelli stated that building a complete and practical quantum network requires many new demonstrations, each tackling a different piece of the puzzle, and that this work specifically addresses the reliable transmission of quantum states over real-world fiber. The researchers are now focused on developing the components necessary for a quantum repeater, a device essential for extending quantum communication over longer distances and lossy fibers, with the ultimate goal of scaling these networks to numerous spatially separated nodes. NIST Researchers Achieve 99% Photon Indistinguishability Over 2 Kilometers Quantum communication networks are progressing from theoretical designs toward tangible systems, yet maintaining the integrity of quantum information over significant distances remains a central hurdle; current networks often struggle with both fidelity and operational speed, limiting their practical application. This accomplishment builds upon techniques initially developed for comparing optical atomic clocks, adapting them to the unique demands of quantum data transmission. This level of stabilization is critical because environmental noise within fiber optic cables can easily corrupt the quantum state of photons traveling to remote network nodes. Building a complete and practical quantum network requires many new demonstrations, each tackling a different piece of the puzzle. Nardelli Co-existence Challenge: Separating Classical & Quantum Signals National Institute of Standards & Technology (NIST) researcher Nick Nardelli and colleagues are tackling a fundamental hurdle in quantum networking: ensuring that the bright classical light used to stabilize fiber optic cables doesn’t overwhelm the delicate quantum signals traveling alongside it. This issue is paramount as researchers strive to build networks capable of distributing quantum information over significant distances, a necessity for applications ranging from distributed quantum computing to secure communication protocols. Nardelli explained that scalable quantum networks could support several emerging technologies such as distributed quantum computing and quantum sensor networks, highlighting the potential impact of this work. The new work, detailed in Optica Quantum, 3, 138-147 (2026), adapts techniques originally developed for comparing optical atomic clocks, renowned for their precision, to stabilize fiber pathways with nanometer-level accuracy. This stabilization is achieved while simultaneously detecting single photons, the carriers of quantum information. Experiments demonstrated the system’s effectiveness over a 2-kilometer fiber link, achieving over 99% indistinguishability between photons traveling through separate, stabilized fibers. They also verified that they were able to cancel out timing jitter added by the fiber to less than 100 attoseconds, ensuring that timing-induced phase errors remain negligible for quantum interference.
The team is now focused on building a complete quantum network, including components like reliable single-photon sources and detectors, to extend quantum communication over even longer distances. Our demonstration combines three capabilities that are rarely achieved together: highly stabilized fiber links, strong separation between the classical stabilization light and the quantum signal – also known as the co-existence challenge – and compatibility with high-bandwidth optical pulses.
Nardelli Path Entanglement Enables High-Bandwidth Quantum State Distribution The promise of a quantum internet, capable of unhackable communication and distributed computing, is edging closer to reality thanks to advances in stabilizing fiber optic cables for quantum signals. This isn’t simply about sending quantum information; it’s about doing so reliably through the noisy channels of existing infrastructure.
The team’s innovation centers on a technique borrowed from the precise world of optical atomic clocks. Experiments showed that photons traveling 2 kilometers maintained over 99% indistinguishability, and timing errors were reduced to less than 100 attoseconds, ensuring minimal disruption to the quantum state. This level of precision is essential for building a network capable of distributing quantum entanglement at scale. In this work, we specifically address how to take carefully prepared quantum states that we generate in the lab and send them to different nodes in the network – over messy, real-world optical fiber – and preserve the quantum information. Nardelli Source: https://www.optica.org/about/newsroom/news_releases/2026/researchers_demonstrate_stable_links_for_quantum_networks_over_kilometers_of_noisy_fiber/ Tags: