Subject C : Continuous variable QKD and its application

M. Yoshida T. Hirano

The aim of the subject C is to develop continuous-variable (CV) QKD and optical secure communication technologies that can be seamlessly integrated into coherent optical communication systems, based on quadrature amplitude modulation (QAM) and homodyne (or heterodyne) detection of coherent light. Such technologies will enable secure and safe communication infrastructure that can offer diverse functions ranging from unconditionally secure communications to high-speed and high-secure data transmission in a unified way.

The CV-QKD system that will be developed in the project will be capable of transmitting information-theoretic secure audio data over a metro network. The optical secure communication system we will develop is based on the combination of QAM technologies and stream cipher. By choosing a physically different 2-dimensional set of QAM signals using stream cipher, an enhanced security of physical-layer encryption will be achieved. We will develop an optical secure communication system operating over a core network with a speed that is compatible with today's high speed optical communication. We also investigate a technology for integrating CV-QKD and optical secure communication system.

Since both CV-QKD and optical secure communication systems exploit devices that are based on the same operating principle as the coherent optical communication, it may be possible in future that an all-in-one sending and receiving equipment offers a full range of secure communication within a tradeoff between the security and speed: by just switching its operation mode, unconditionally secure metro communication and physically secure core communication, and also computationally secure high-speed communication will be available.