TSUJINO Kenji    Department   School of Medicine, School of Medicine    Position   Associate Professor
Article types	Original article
Language	English
Peer review	Peer reviewed
Title	Quantum Receiver beyond the Standard Quantum Limit of Coherent Optical Communication
Journal	Formal name：Physical review letters Abbreviation：Phys Rev Lett ISSN code：00319007
Volume, Issue, Page	106,pp.250503
Author and coauthor	Kenji Tsujino†, Daiji Fukuda, Go Fujii, Shuichiro Inoue, Mikio Fujiwara, Masahiro Takeoka, Masahide Sasaki
Authorship	Lead author
Publication date	2011/06
Summary	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.