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1The First Medium-Term Plan (FY2001-2005)e rst study performed by the laboratory was on a basic principle of quantum communication, which is a demonstration experiment of coding technology that real-izes ultimate communication eciency. As a background, the quantum communication eld faced a major turning point in 1995. at is, the US-UK joint theoretical study team led by Schumacher convincingly proved the conjec-ture of the Holevo limit on the capacity of quantum com-munication and the existence of communication that 1 IntoroductionMasahide SASAKIThe real form of information running through smartphones, PCs and the Internet is a series of a vast amount of electric and photon pulses in the form of digital signals of 0 and 1. The information concept that uses these binary digits (bit) was established in 1948 as “Information Theory” by Shannon. Around the same time, in 1950, Gabor suggested that communication channel capacities may be increased beyond the Shannon limit by combining Shannon’s theory with quantum mechanics to control electromagnetic waves at the level of photons which are the smallest unit of electromagnetic energy. This is how the concept of quantum communication was born. The new era of lasers began in 1960 when Maiman succeeded in laser oscillation. The frequency of a laser is 100,000 times greater than that of a radio frequency wave. The temperature of a photon at that frequency is equivalent to 10,000°C, which is much higher than thermal noise. Hence, the particle nature of electromagnetic waves, namely the quantum nature as “photons” can be clearly observed. The technology to achieve quantum communication became a real possibility and basic theoretic research has been performed since then.In 1982, a physicist named C. H. Bennett and a cryptographer named G. Brassard met by chance and had dialogue poolside at a hotel in Puerto Rico. Quantum cryptography, often referred to as quantum key distribution (QKD), was born from this conversation. On 1985, D. Deutsch developed multi-universe cosmology. He introduced the idea of the “quantum bit,” which can be both 0 and 1 simultaneously, to formulate quantum computing. The idea replaced the conventional 0 and 1 concept. In 1994, P. Shor discovered a quantum calculation computing to solve discrete logarithm problems at high speed. He demonstrated that quantum computers, if realized, may decrypt modern cryptography in several minutes. Since then, many papers on quantum communication, quantum cryptography and quantum computing have been published that have led to the emergence of quantum information science.At around that time, research on quantum communication started at the Communication Research Laboratory (CRL, predecessor of NICT). In the Laboratory of Optical Data Processing, theoretical research on quantum communication started at that time. Since 1999, research on quantum info-communication technology (quantum ICT) to unite quantum communication, QKD, and quantum computing started. This project was supported by the Ministry of Posts and Telecommunication. The industry, university and government collaborate to design research and development strategies in Japan. In 2001, the Laboratory of Quantum Information Technology was established and full-fledged efforts to research and develop quantum ICT began in coordination with the commissioned research on QKD funded by the Telecommunications Advancement Organization of Japan (TAO).11 Intoroduction