A world-record achievement in the 100-kilometer practical quantum secure direct communication rate

ecently, Long et al. [1] at the Beijing Academy of Quantum Information Sciences, in collaboration with the partners, proposed the theory of oneway quantum secure direct communication (QSDC) and successfully developed a practical system.This achievement set a world record for long-distance stable transmission, demonstrating a rate of 2.38 kbps at a distance of 104.8 km over 168 hours.QSDC was first proposed by Long and Liu in 2000 [2], with the goal of enabling secure and reliable communication over a quantum channel subject to both noise, loss, and eavesdropping [3-5].It features characteristics such as eavesdropping detection, eavesdropping prevention, compatibility with existing networks, simplified management processes, and covert transmission [6], making it highly promising for next-generation secure communication [7].The theory of QSDC has evolved rapidly, and many variants of the QSDC protocol have been proposed [8-27].To mitigate vulnerabilities in quantum devices, researchers have developed innovative protocols including: (i) measurement-device-independent QSDC (MDI-QSDC) [9-11], which enhances security at detection nodes by outsourcing Bell-state measurements to untrusted third parties; (ii) reference-device-independent QSDC (RDI-QSDC) [12], which reduces reliance on receiving devices through statistical characterization of signals; (iii) passive-source QSDC [13-15], which eliminates source-side security vulnerabilities by avoiding active modulation operations; and (iv) device-independent QSDC (DI-QSDC) [16-19], which achieves unconditional security guarantees by verifying Bell inequality violations to circumvent assumptions about source and detector.In addition, quantum error-correcting codes have been integrated into QSDC frameworks [20], significantly improving