Quantum Secure Direct Communication with Quantum Memory

TLDR

Quantum communication offers absolute security, and quantum secure direct communication (QSDC) enables high‑security, instantaneous message transmission, but practical implementation requires quantum memory to control message transfer in time. The study experimentally demonstrates QSDC using advanced atomic quantum memory for the first time. The protocol encodes messages in photon polarization and achieves about 90 % entanglement‑decoding fidelity. The experiment marks a key step toward practical QSDC and shows its viability for long‑distance quantum networking.

Abstract

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 Letter, we report the experimental demonstration of QSDC with state-of-the-art atomic quantum memory for the first time in principle. We use the polarization degrees of freedom of photons as the information carrier, and the fidelity of entanglement decoding is 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.