Abstract: Because the atmosphere is full of noise and interference, long-distance quantum communication in free space has become a problem. Based on the principle of entangled quantum state exchange, a quantum channel is established indirectly at both ends through two relay points, which makes the transfer of quantum information over long distances possible. By studying the quantum states of the source and the relay point under different circumstances, the quantum state of the receiving end is imposed on different logic gates for corresponding logic transform. As a result, the information sent by the source side is gotten. In addition, this paper studies the systems with N relay points and solves the problem of quantum information transmission over long distances.

Key words: quantum communication, entanglement exchange, quantum repeater

摘要： 由于大气中充满噪声与干扰，在自由空间中进行远距离的量子通信成为一个难题。基于量子态纠缠交换的原理，通过两个中继点间接地在通信两端建立起量子信道，使得远距离量子信息的传输成为可能；通过研究源端及各中继点在不同情况下的量子态及接收端相应的量子态，进而对接收端所拥有的量子态施加不同逻辑门进行相应的逻辑变换，最终成功得到了源端所发出的信息；对具有N个中继点的系统进行了研究，解决了远距离的量子信息传输问题。

关键词: 量子通信, 纠缠交换, 量子中继