China achieves a new record fiber QKD transmission distance of over 509 km

QKD SNS-TF - Credit: Chen et al.

Researchers at the University of Science and Technology of China and Tsinghua University have recently achieved an unprecedented quantum key distribution (QKD) transmission distance using the SNS-TF protocol.

The sending-or-not-sending twin-field (SNS-TF) protocol has so far proved to be a highly promising strategy for achieving high rates over long distances in QKD applications. In fact, by tolerating large misalignment errors, this protocol can surpass the repeaterless bound in more effective ways, which is a crucial factor in the realization of long-distance QKD.

The SNS-TF protocol was developed and introduced in a previous research effort by some of the researchers who wrote the recent paper. In previous studies, the protocol proved to be highly advantageous for QKD applications, particularly for achieving long distance transmission.

Using their SNS-TF approach, the researchers achieved a secure key rate at 509 km, over seven times higher than the relative repeaterless bound QKD, and with the same detection loss. Remarkably, the key rate they achieved is also higher than that achieved by more traditional QKD protocols running on a perfect repeaterless QKD device.

Their paper, has been published in Physical Review Letters.

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