Long-distance twin-field quantum key distribution with entangled sources
This work addresses long-distance secure communication for quantum networks, representing an incremental improvement over existing TFQKD variants.
The authors tackled the problem of transmission distance limits in twin-field quantum key distribution (TFQKD) by proposing a scheme using an entangled coherent state source, achieving a theoretical distance advantage of 400 kilometers with robustness against errors.
Twin-field quantum key distribution (TFQKD), using single-photon-type interference, offers a way to exceed the rate-distance limit without quantum repeaters. However, it still suffers from the photon losses and dark counts, which impose an ultimate limit on its transmission distance. In this letter, we propose a scheme to implement TFQKD with an entangled coherent state source in the middle to increase its range, as well as comparing its performance under coherent attacks with that of TFQKD variants. Simulations show that our protocol has a theoretical distance advantage of 400 kilometers. Moreover, the scheme has great robustness against the misalignment error and finite-size effects. Our work is a promising step toward long-distance secure communication and is greatly compatible with future global quantum network.