量子安全直接通信不同于量子密钥分发，它可在量子信道中直接传递机密信息，是一种新的量子通信模式。量子密钥分发不能避免发现窃听前的信息泄露，只能传输随机的密钥。量子安全直接通信不但能发现窃听，而且能避免发现窃听前的信息泄露。量子安全直接通信协议提出之后，在理论上得到了迅速发展，如何在实际环境下实现量子安全直接通信成为今后的重要发展方向。由于量子系统不可避免地受到周围环境的影响，为了实际应用必须研究噪声情况下的量子安全直接通信。本项目着重研究量子一次便笺和两步直接通信两个重要的量子直接安全通信方案在自由空间和光纤中的理论与实验研究，研究噪声对这两种协议的影响，提出噪声环境下量子直接安全通信的实现方案。

Quantum secure direct communication (QSDC) is a new quantum communication mode in which secret information can be transmitted securely and directly over quantum channels， which is differently from quantum key distribution (QKD). QSDC can not only detect eavesdropping, but also avoid information leakage transmitted before finfding eavesdroper. Since it was first proposed， QSDC has been theoretically developed very fast, and QSDC under practical environment is becoming an important issue. Because real quantum systems are hardly avoidable from their surrounding environments, it is necessary to study QSDC over noisy channels. In this project, we focus on the theoretical and experimental studies of the two-step and one-time-pad protocols over the optical fiber and free space，and study the effect of the noise on the two protocols, and propose methods for implementing QSDC in noisy environment.