Quantum secure direct communication (QSDC) is an important branch of quantum communication, based on the principles of quantum mechanics for the direct transmission of classified information. While recent proof-of-principle experimental studies have made remarkable progress; QSDC systems remain to be implemented in practice. In a recent study, Ruoyang Qi and co-workers at the departments of low-dimensional quantum physics, information technology, electronics and information engineering, proposed and experimentally implemented a practical quantum secure communication system.