Practical Quantum Secure Direct Communication

Quantum secure direct communication (QSDC) transmits information securely through a quantum channel, distinct among various quantum communications. Proposed by me and Liu 20 years ago, QSDC has now been developed to a stage that is ready for practical application. QSDC advances classical communication of reliable communication over a noisy channel, which is guaranteed by Shannon's theory, to a higher plane of both secure and reliable communication over a noisy channel even in the presence of eavesdropping. Here we briefly introduce the basic principles, the techniques for practical applications.