Construction begins on Japan's first wide-area quantum cryptography communication network spanning approximately 600km across Tokyo, Nagoya, and Osaka

NTT Docomo Business, Ltd. (formerly NTT Communications Corporation, hereinafter referred to as NTT Docomo Business), Toshiba Corporation (hereinafter referred to as Toshiba), and NEC Corporation (hereinafter referred to as NEC) have commenced the construction of a wide-area quantum cryptography communication network spanning approximately 600km, connecting the three major metropolitan areas of Tokyo, Nagoya, and Osaka (hereinafter referred to as the Tokyo-Nagoya-Osaka region). This initiative is part of the efforts by the Ministry of Internal Affairs and Communications and the National Institute of Information and Communications Technology (NICT) towards the social implementation of quantum key distribution. Following its construction, demonstration experiments using this network for quantum key distribution will be conducted.

This demonstration aims to foster promising use cases by verifying secure communication using quantum technology, with a view to social implementation in industries such as healthcare, finance, and electric power, which handle highly confidential data including national security information and personal data.

1. Background In recent years, as society transitions towards advanced AI and increased data utilization, the need to collaborate and utilize diverse data, including critical data, across organizations and regions has grown. Concurrently, advancements in quantum computing technology raise concerns about the degradation of the cryptographic strength of existing encryption technologies, whose security relies on computer performance.

Consequently, the importance of new communication technologies for long-term secure protection of highly confidential information, as well as secure operation and key management, is increasing. In particular, addressing the "Harvest Now, Decrypt Later" (HNDL) risk, where current communication is intercepted and stored for future decryption by quantum computers, is a critical challenge from the perspectives of national security, economic security, and industrial competitiveness.

Against this backdrop, attention is focusing on Quantum Key Distribution (QKD), a technology that can achieve extremely secure communication, and quantum cryptography communication, which uses cryptographic keys from QKD for secure communication. NICT has previously conducted technical demonstrations utilizing the "Tokyo QKD Network." This demonstration will significantly expand those efforts to the Tokyo-Nagoya-Osaka region, establishing Japan's largest wide-area quantum cryptography communication network.

2. Key Technologies Utilized in the Demonstration

- Quantum Key Distribution (QKD): A technology that securely shares cryptographic keys between communication partners using the principles of quantum mechanics. Unlike conventional cryptography, which depends on computational power, QKD is theoretically capable of detecting eavesdropping and preventing key duplication. Furthermore, by combining QKD with a "one-time pad" for secure data encryption, information-theoretically secure quantum cryptography communication can be realized.

- Quantum-Secure Cloud: A technology that realizes secure transmission, storage, and utilization (confidential computation) of highly confidential data by building a distributed storage system utilizing secret sharing protocols on a QKD network. Secret sharing divides data into multiple parts and stores them distributively; even if less than a threshold amount of data is leaked, information about the original data cannot be obtained, providing "information-theoretic security."

3. Overview of This Demonstration

This demonstration will construct a wide-area quantum cryptography communication network spanning the Tokyo-Nagoya-Osaka region, a first in Japan. It will verify the performance, stability, and security of quantum cryptography communication in long-distance environments, as well as the ease of network operation for practical use. By involving users from various industries, the feasibility of secure wide-area distribution of highly confidential data and cross-organizational data collaboration will be examined.

In addition to technical verification, this initiative will promote the consideration of business models and the development of new application areas and users, with a view to the social implementation of quantum cryptography communication. Through interviews with participating users, challenges and expectations from the user perspective will be identified, and efforts will be made towards the practical realization of a wide-area quantum cryptography communication network.

<Conceptual image of the wide-area quantum cryptography communication network construction spanning approximately 600km across Tokyo, Nagoya, and Osaka>

4. Roles of Each Company in This Demonstration

- NTT Docomo Business: Overall demonstration supervision, technical verification & user demonstration, social implementation study, provision of network, data center, and applications. - Toshiba: Provision of quantum key distribution equipment, construction of quantum key distribution network, technical verification & user demonstration. -NEC: Provision of quantum key distribution equipment, construction of quantum key distribution network, technical verification & user demonstration.

In addition to these three companies, collaborations will also be pursued with Exeo Group Inc., Exeo Digital Solutions Inc., NTT ME Corporation, Deloitte Tohmatsu LLC, and SAKURA Internet Inc.

5. Future Outlook

The three companies will continue to study and verify with participating users and others towards the social implementation of QKD networks by 2030, as envisioned by the Ministry of Internal Affairs and Communications.

*1: A wide-area quantum cryptography communication network is a demonstration environment for verifying the performance, stability, security, and operability of quantum key distribution over a wide-area network connecting Tokyo, Nagoya, and Osaka. *2: Harvest Now, Decrypt Later (HNDL) is a cyberattack aimed at collecting and accumulating encrypted communication data now for future decryption with technological advancements. It is recognized as a new security risk, implying that "current communications may also be decrypted in the future." *3: The Tokyo QKD Network is a testbed for quantum key distribution (QKD) networks built and operated by NICT in the Tokyo metropolitan area since 2010. *4: As of June 30, 2026, according to research by the three companies. *5: Refers to the future vision presented in related materials from the Ministry of Internal Affairs and Communications. For details, please refer to the following:

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