Chinese scientists have achieved an important milestone in the field of quantum communication. They have set a new world record by successfully implementing twin-field quantum key distribution (QKD) over a 1,002-kilometer optical fiber. This remarkable accomplishment represents a significant stride towards establishing a large-scale quantum network in the future.
QKD is a crucial technique in quantum communication that enables two distant users to generate a shared key, known only to them, which is then used for encrypting and decrypting messages. However, the practical application of QKD faces a major obstacle—the distance limit. This is because quantum signals cannot be amplified, and the transmittance of the channel decreases exponentially with increasing distance.
Previously, twin-field QKD had only been demonstrated in laboratory settings using spooled fiber with a maximum length of 830 kilometers.
In a study published in the journal Physical Review Letters, scientists from esteemed institutions such as the University of Science and Technology of China, the Jinan Institute of Quantum Technology, and the Shanghai Institute of Microsystem and Information Technology detailed their accomplishment. They reported achieving a record distribution distance of 1,002 kilometers, with a secure key rate of 0.0034 bits per second.
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During their experiments, the scientists developed innovative techniques such as dual-band phase estimation and ultra-low noise superconducting nanowire single-photon detectors. These advancements helped suppress system noise, which had previously hindered the production of secure keys over long distances.
The study not only demonstrates the feasibility of twin-field QKD over extremely long distances but also provides valuable insights into the future of long-haul quantum communication. The University of Science and Technology of China highlights the promising prospects this breakthrough holds for the field.