Jiu-Peng Chen

Channel loss is one of the most severe limitation to extend the transmission distance of quan- tum key distribution in practice. The twin-field quantum key distribution can achieve a much longer transmission distance with improving the key rate from the linear scale of channel loss in the traditional decoy-state method to the square root scale of the channel transmittance. Here we demonstrate the real-optical-fibre experimental results of twin-field quantum key distribution through the sending-or-not-sending protocol, which is fault tolerant to large misalignment error. The phase locking technology developed in the frequency transfer field is adopted to ensure Alice’s and Bob’s source wavelengths are locked to each other. Phase reference pulses are used to monitor the phase difference between the channel. Further with a high performance single photon detector, we obtain the positive key rates for different distances, specifically, the obtained secure key rate at 150 km is higher than that of the measurement device independent QKD.

Quantum key distribution (QKD) holds the potential to establish secure keys over long distances. The distance of point-to-point QKD secure key distribution is primarily impeded by the transmission loss inherent to the channel. In the quest to realize a large-scale quantum network, increasing the QKD distance under current technology is of great research interest. Here we adopt the 3-intensity sending-or-not-sending twin-field QKD (TF-QKD) protocol with the actively-odd-parity-pairing method. The experiment demonstrates the feasibility of secure QKD over a 1002 km fibre channel considering the finite size effect. The secure key rate is $3.11 10^{-12}$ per pulse at this distance. Furthermore, by optimizing parameters for shorter fiber distances, we conducted performance tests on key distribution for fiber lengths ranging from 202 km to 505 km. Notably, the secure key rate for the 202 km, the normal distance between major cities, reached 111.74 kbps.