The Experimental Research Of Quantum Information Via Free-Space Channels

Quantum information is an interdisciplinary science between quantum physics and information science, which provides a new way for better understanding of quantum theory. Furthermore, due to its unique advantages in information processing and quantum information rapidly become one of the hottest researches in recent years.Free-space channels near earth atmosphere can be used to study the feasibility of establishing the global-scale quantum communication based on satellites as well as testing the fundamental problems in quantum theory. In view of the above reasons, this thesis reports the experimental designs, implementations and results on quantum information via free-space channels. A high quality and high brightness entanglement source, the compact optical transmitting and receiving devices and the acquiring, pointing and tracking technique are developed for the free-space quantum information experiments.In order to test the feasibility of quantum communication based on space platforms, we perform an experiment on quantum key distribution using the entanglement-based efficient BB84protocol via16km free-space optical channels and achieve an optimal final secure key rate. We realize a free-space quantum teleportation over100km. An average fidelity of80.4(9)%can be achieved for six different initial states over a35-53dB loss quantum channel. This experiment shows the feasibility of satellite-based ultra-long-distance quantum teleportation. We achieve an experiment of single-photon transmission from satellite to earth by exploiting a satellite equipped with cube-corner retroreflector. A mimic quasi-single-photon source is located on satellite Champ whose orbit has a perigee height of400km. The average photon number per pulse and the divergence angle of the mimic source is0.85and38μrad respectively. The results obtained from this experiment verify the feasibility of future satellite-to-ground quantum communication.In order to test the fundamental issues of the laws of quantum theory:we demonstrate entanglement distribution over a two-link channel, in which the entangled photons are separated by101.8km. Violation of the Clauser-Horne-Shimony-Holt inequality is observed without the locality loophole; we distribute entangled photon pairs over two sites in the same latitude via free-space optical links. We develop long-distance laser tracking and synchronization technology, based on which, we take a12-hour continuous, space-like CHSH-Bell inequality measurement with the freedom of choice. This experiment demonstrates that the lower bound speed of’spooky action’ is four orders of magnitude higher than the speed of light if the Earth’s speed in any inertial reference frame is less than10-3times of speed of light.