China team boosts atom entanglement distance record fourfold

Chinese scientists have pushed the boundaries of quantum technology, successfully achieving the entanglement of cold atoms across a record-breaking distance of 420 kilometers (260 miles). This significant achievement, detailed in the journal Physical Review Letters, is seen as a crucial step toward building quantum networks that can span entire cities.

The entanglement distance achieved is more than four times greater than previous demonstrations, surpassing the threshold where direct transmission faces fundamental physical limitations. The research team, including prominent physicist Pan Jianwei from the University of Science and Technology of China, stated that their experiment serves as a vital testbed for exploring quantum network applications beyond metropolitan scales.

To achieve this feat, the researchers employed two quantum memory units. Each unit contained clouds of laser-cooled rubidium atoms positioned 420 kilometers apart and linked by an optical fiber. Quantum entanglement is a phenomenon where two or more particles become interconnected, sharing a unified quantum state irrespective of the distance separating them.

While entangling light particles over long distances, including through optical fiber, has been accomplished before, the integration of quantum memory introduces a new layer of complexity to the process. This advancement holds promise for future developments in secure communication and advanced computing.

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Our experiment provides a test bed for studying quantum-network applications beyond the metropolitan scale.