Entanglement-based quantum key distribution via 343 km fiber link with multiple wavelength polarization state compensation

Long-distance entanglement distribution is fundamental to the establishment of a large-scale quantum network, particularly in systems that operate without the need for trusted relays. Here, we demonstrate entanglement-based quantum key distribution over 343 km of fiber spools using multi-wavelength single-photon-level calibration light for reference frame alignment. By co-propagating calibration and entangled photons through identical paths and sharing detectors in a time-multiplexed manner, a polarization purity of 2783 achieves for two mutually unbiased bases. The system operates continuously for 27.1 h in the laboratory, generating a total of 253 bits secure key at an asymptotic secure key rate of $3.68\times{10^{-3}}$ bps. This work provides a viable approach for constructing large-scale quantum network.