The Quantum Information Science Research Institute at Tamagawa University was established in April 2011 as an expansion of the Quantum Information Science Research Center, which had previously belonged to the Tamagawa University Academic Research Institute. The Quantum Information Science Research Center founded the International Conference on Quantum Communication in 1990, a leading global conference in the field of quantum information and communication. The center managed the conference for 20 years before transferring its operation to the international steering committee in 2010. During this period, the academic foundations of quantum information science rapidly advanced, and promising quantum Today, research and development in quantum technologies—including those mentioned above—are actively pursued worldwide, with expectations of transformative changes in computing, communication, cryptography, and sensing technologies. Quantum cryptographic communication, which utilizes quantum technologies, is theoretically capable of achieving more secure communication than conventional methods and is expected to contribute to the development of safer and more reliable networks. At the Quantum Information Science Research Institute, we are developing theoretical frameworks for quantum cryptographic technologies applicable to high capacity, long-distance data transmission. We are experimentally verifying the coexistence of high security and excellent communication performance. In addition, we are conducting research in areas such as quantum communication theory and quantum coding theory. We remain committed to advancing fundamental research in cutting-edge quantum information science, while also promoting applied research such as quantum cryptographic communication technologies, with the aim of realizing practical implementations in society.