  Quantum communication provides an absolute security advantage, and it has
been widely developed over the past 30 years. As an important branch of quantum
communication, quantum secure direct communication (QSDC) promotes high
security and instantaneousness in communication through directly transmitting
messages over a quantum channel. The full implementation of a quantum protocol
always requires the ability to control the transfer of a message effectively in
the time domain; thus, it is essential to combine QSDC with quantum memory to
accomplish the communication task. In this paper, we report the experimental
demonstration of QSDC with state-of-the-art atomic quantum memory for the first
time in principle. We used the polarization degrees of freedom of photons as
the information carrier, and the fidelity of entanglement decoding was verified
as approximately 90%. Our work completes a fundamental step toward practical
QSDC and demonstrates a potential application for long-distance quantum
communication in a quantum network.
