Extended Data Fig. 1: Key rate–distance results in the integrated-photonics TF-QKD network.

The coloured diamond points represent experimental results for the TF-QKD network with ten paired QKD client chips {A_i, B_i} through ten different wavelengths, in which i = (1, 2,…, 10) indicates the paired chips. The grey line and dash-dotted blue line indicate simulation results using the experimental parameters and ideal parameters in the finite-key and asymptotic cases, respectively. The dashed red line indicates the PLOB-repeaterless bound. The plot defines three regions: (1) traditional communication limit (below PLOB); (2) present TF-QKD performance (exceeding PLOB with experimental constraints); and (3) future TF-QKD potential (with technical improvements). Two configurations were implemented in the experiment: case 1: 204-km upstream fibres that do not exceed the PLOB bound and case 2: 370-km upstream fibres that do surpass the PLOB bound. The 204-km configuration was used to verify that our chip-based TF-QKD network follows the expected theoretical key rate–distance relationship. At a distance of 370 km, all TF-QKD across 20 client chips successfully exceed the PLOB-repeaterless bound. The network used short downstream fibres, except for the {A₅, B₅} chips with 120-km downstream fibres.