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1IntroductionWith the ever increasing prevalence of smartphones and the Internet, the pursuit of higher eciency and ac-curacy of information propagation have become increas-ingly urgent. By the same token, it has become a serious concern that the communication capacity of trunk lines, where a tremendous amount of information comes and goes, will sooner or later reach its technological limits. e hitherto terrestrial-bounded communication range is now embracing near outer space surrounding the earth thanks to satellite networks, and the need for interstellar high speed communication—between the moon, Mars, and earth—must be addressed in the near future. In such ultra-long distance space communication, even the optical signal suers severe diusion, resulting in extremely weak re-ceived intensity and limitations of communication speed due to quantum noise which is intrinsically contained in light. To overcome such challenges, the signal reception technologies must utilize all possibilities to exploit infor-mation from optical signals. Recent achievements in quantum information theory have demonstrated that, to realize ultimate transmission capacity limited only by the laws of physics, the receiver must decode the signal with a concurrent performance of inter-signal pulse quantum calculations. Such process can evolve macroscopic super-position of quantum states, oen called “Schrödinger’s cat,” within the decoding circuit, as well as quantum entangle-ment (correlation among the signal pulses in quantum domain). Future technologies must be able to control such phenomena to perform successful measurements. e re-ceiving device capable of such control is called an optimized quantum receiver, or quantum decoder.As described elsewhere in this special issue, quantum technology can also provide ultimate security in crypto-graphic technology, i.e. quantum cryptography. However, the feeble laser light (coherent light) approach now under progress toward commercialization has limitations in terms of communication distance and key generation rate. Development of private key relaying method, as well as provision of very many trusted nodes are needed to over-come such limitations. Many attempts toward realization of quantum cryptography networks, now under verication stage worldwide, invariably have opted for this approach. A serious challenge inherent to this approach is its vulner-ability to hijacking: if any one node between two remotely separated locations is hijacked by an attacker with mali-cious intent, the secret key and related information may easily be taken out. A technology, called a quantum re-peater, is expected to ll the gap. A quantum repeater makes use of a photon pair with special mutual correlation, called quantum entanglement, instead of feeble laser light to transmit information. rough quantum mechanical handling at each repeater point, the photon pair can be transferred to the next repeater point without its entangle-ment relation being corrupted through its exposure to measurement. is approach promises to realize much larger communication distance than that enabled using 4 Quantum Node Technology4-1 Optical Quantum Control TechnologiesMasahiro TAKEOKA, Mikio FUJIWARA, Kentaro WAKUI, Ruibo JIN, Yoshiaki TSUJIMOTO, Shuro IZUMI, and Masahide SASAKIIn information and communication networks, transmission capacity and security are main technical demands that are required to be continuously and rapidly upgraded. To use the maximum physical potential of the network, one has to develop “quantum node technology” which enables us to control quantum states of light and matters to achieve the ultimate communication capacity and sensitivity. In this article, we review our recent progress toward this goal, in particular, the technical progress of the quantum control photonic signals and demonstration of new quantum communication protocols by using these technologies.494 Quantum Node Technology