Experimental Long-Distance Quantum Communication

Quantum Information (QI), a young discipline as cross-field of quantum physics and information science, has been recently attracting world-wide emphasis and greatly developing for its advantages and foreground compared to classical information technology. Quantum communication, of which technology would dramatically improve the security, capability and efficiency of information communication, is one of the most rapidly developing fields of quantum information, and is important strategic direction of information technology in future. Because the weak coherent laser resource has defects in security and it is difficult to realize over hundred kilometers'quantum communication on fiber based channel, entanglement-based free-space quantum communication becomes a new research focus. Free-space quantum communication has the excellence of high stability, low losses, extreme low decoherence for polarization-code quantum bit, makes it to be generally considered as the most feasible option for the global quantum communication.This work is mainly about the key difficulties of long-distance quantum communication (LDQC) which need to be overcome, describes the realization of a series of LDQC experiments that I involved and led. With the high intensity resource of polarization entangled photon pairs, we realized the longest distance free-space quantum teleportation up to 16km between two spots in the district of the Badaling Great Wall in Beijing; we also experimentally realized the 13km long distance free-space quantum entanglement distribution and quantum key distribution in Hefei, for the first time proved the feasibility of satellite-based entanglement distribution; carried out the experiment of non-locally entangled two independent single photon resources; experimentally demonstrated decoherence-free subspace based quantum communication without shared frame; proposed and implemented the experiment of time-tag assistant quantum error-free transmission, shows that the large scale fiber-based error-free transmission of the quantum bit in polarization space is practical and advanced.The technology developed in our experiment will be in future of importance in many significant scientific fields such as long-distance quantum communication, quantum information and elemental examinations of quantum mechanics.