Quantum receiver beyond the standard quantum limit of coherent optical communication

• Published in: Physical review letters Vol. 106; no. 25; p. 250503
• Main Authors: Tsujino, Kenji, Fukuda, Daiji, Fujii, Go, Inoue, Shuichiro, Fujiwara, Mikio, Takeoka, Masahiro, Sasaki, Masahide
• Format: Journal Article
• Language: English
• Published: United States 24.06.2011
• ISSN: 1079-7114
• DOI: 10.1103/physrevlett.106.250503

The most efficient modern optical communication is known as coherent communication, and its standard quantum limit is almost reachable with current technology. Though it has been predicted for a long time that this standard quantum limit could be overcome via quantum mechanically optimized receivers, such a performance has not been experimentally realized so far. Here we demonstrate the first unconditional evidence surpassing the standard quantum limit of coherent optical communication. We implement a quantum receiver with a simple linear optics configuration and achieve more than 90% of the total detection efficiency of the system. Such an efficient quantum receiver will provide a new way of extending the distance of amplification-free channels, as well as of realizing quantum information protocols based on coherent states and the loophole-free test of quantum mechanics.