1905年爱因斯坦首次提出“光量子”概念,标志着“量子光学”诞生,并有力推动其后“量子力学”的创建。本文将简述“光量子”如何诞生,“光子”有何奇异特性,着重介绍“光子”在量子信息领域的应用,包括量子密码、量子纠缠网络、量子模拟、量子计量和量子计算等。最后研讨“光子究竟是什么”。

In 1905, Albert Einstein first proposed the idea of light quantum. That was the beginning of quantum optics, and it helped to initiate the quantum physics. In this report, we will briefly describe how "light quantum" is born and the bizarrerie characteristics of photons, emphatically we introduce its applications in quantum cryptography, quantum networks, quantum simulation, quantum metrology and quantum computing. At the end of the paper, we will discuss the outstanding issue, the nature of light.