We develop an information-theoretic analysis of Quantum-Memory-Free (QMF) Quantum Secure Direct Communication (QSDC) under collective attacks as an alternative to the use of a conventional Quantum Key Distribution (QKD) protocol in conjunction with one-time pads. Our main contributions are: 1) a QMF-QSDC protocol that only relies on universal hashing of coded sequences without wiretap coding; 2) a set of privacy amplification theorems for extracting secrecy from coded classical sequences against quantum side-information. These tools open the way to the design of effective QMF-QSDC protocols.
@article{arxiv.2601.21265,
title = {A Quantum-Memory-Free Quantum Secure Direct Communication Protocol Based on Privacy Amplification of Coded Sequences},
author = {Shang-Jen Su and Shi-Yuan Wang and Matthieu R. Bloch},
journal= {arXiv preprint arXiv:2601.21265},
year = {2026}
}