Experimental realization of quantum cryptography communication in free space

• Published in: Science China. Physics, mechanics & astronomy Vol. 48; no. 2; pp. 237 - 246
• Main Author: WANG, Chuan
• Format: Journal Article
• Language: English
• Published: Beijing Springer Nature B.V 01.04.2005; Center for Atomic and Molecular NanoSciences, Tsinghua University, Beijing 100084, China; Department of Physics, Key Laboratory for Quantum Information and Measurements, Tsinghua University, Beijing 100084, China%Department of Physics, Key Laboratory for Quantum Information and Measurements, Tsinghua University, Beijing 100084, China
• Subjects: Photons; Quantum cryptography; Signal transmission; quantum key distribution; linear optics; free space; faint pulses
• ISSN: 1672-1799; 1674-7348; 1869-1927
• DOI: 10.1360/04YW0185

Utilizing linear optical devices, the principle of B92 quantum key distribution (QKD) protocol is demonstrated in free space with a distance of transmission of 2.2 meters. The faint laser pulses with 650 nm wavelength are used as the single photon sources. The experimental results show that the eavesdropping behavior in the signal transmission can be detected. We also discuss the problems and solutions in using the quantum cryptography communication practically. It is pointed out that one of the approaches to increasing the distance of the quantum communication is to overcome the attenuation of the single photon in transmission. This could not be solved by the use of single photon source, and new quantum communication protocols are needed to solve these problems.