OKI Electric Industry announced that it has developed a quantum entangled light source that offers the highest purity level achieved to date. OKI has successfully developed a quantum entangled light source based on cascaded nonlinear optical effects using a proprietary periodically poled lithium niobate ridge-waveguide device operating at room temperature. Research led by professor Shuichiro Inoue at the Institute of Quantum Science at Nihon University confirms a signal-to-noise ratio more than 100-fold better than that of optical fiber light sources. These tests show that the signal-to-noise ratio for the photon pairs generated is one to two orders of magnitude greater than for conventional light source and detector combinations, and demonstrate the feasibility of quantum cryptography communications at low signal error rates, using the quantum entangled light source developed in this research program and the single-photon detector. Using standard optical fibers, the team successfully transmitted the quantum entangled photon pairs over a distance of 140 km, demonstrating the feasibility of next-generation quantum cryptography communication systems for metropolitan area coverage. “They (quantum cryptography technologies) have attracted attention as an exceedingly high-security service for a smart community due to their potential to achieve indecipherable encoding,” said Takeshi Kamijoh, general manager of the Research and Development Center at OKI. “A number of major hurdles confront research and development teams working to achieve practical applications, including the need for ultralow-temperature cooling for light sources and the generation of light at wavelengths beyond the optical communications band, as well as difficulties achieving the photon purity needed.” OKI will continue to refine the quantum entangled light source while working to reduce size and cost. Its goal is to achieve a practical quantum cryptography communications system. For more information, visit: www.oki.com