Miles ahead: China team boosts atom entanglement distance record fourfold
Chinese scientists have achieved the quantum entanglement of cold atoms across a record-breaking 420km (260 miles), a breakthrough they say lays the groundwork for intercity quantum networks. According to a paper published by the peer-reviewed journal Physical Review Letters on August 11, the distance was more than four times previous demonstrations and exceeded the threshold at which direct…
Chinese researchers have shattered the record for quantum entanglement distance by successfully linking cold atoms over a staggering 420km, more than quadrupling previous accomplishments. This groundbreaking development, detailed in a recent report in Physical Review Letters, marks a significant leap towards the creation of intercity quantum networks.
The team, led by Professor Pan Jianwei from the University of Science and Technology of China in Hefei, Anhui province, utilized two quantum memory units separated by the immense distance, each composed of laser-cooled clouds of rubidium atoms. These units were connected via an optical fiber link, with the ultimate goal being to achieve entanglement—a phenomenon where particles become interconnected, sharing a joint quantum state regardless of physical distance.
Quantum entanglement has long fascinated scientists due to its ability to link particles in ways that defy classical physics, though implementing this in real-world applications, especially over long distances, presents considerable challenges. Traditional methods of transmitting quantum information over long distances suffer from significant signal loss, making it difficult to maintain the delicate quantum states necessary for entanglement.
To tackle these hurdles, the researchers employed several advanced techniques. They implemented a system designed to continuously correct for fluctuations, ensuring that the quantum states remained synchronized across the entire network. Additionally, they adjusted the operating wavelength of the quantum memory units, significantly reducing signal transmission losses.
These innovations enabled the team to surpass the theoretical maximum for quantum data transmission without the use of repeaters or memory devices, achieving entanglement beyond 320km—far surpassing the limitations imposed by lossy communication channels. This achievement not only sets a new benchmark in quantum communication but also paves the way for scalable quantum networks capable of information sharing and coordinated operations over vast distances.
The success builds on a decade of research by the team, including their 2020 demonstration of entanglement between quantum memory units across 50km of fiber optic cable. Pan Jianwei's team has continuously pushed the boundaries of quantum technology, recently establishing the world’s first three-node quantum network in 2024. Their work in quantum encryption, detailed in a 2024 Science paper, showcased secure information transfer over 100km of fiber optic cable without relying on the trustworthiness of individual devices.
This latest milestone underscores the rapid advancements in quantum science, highlighting China's pivotal role in shaping the future of quantum technology.
Written by urgent.news from South China Morning Post's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
