September 21, 2023
SoftBank Corp. (“SoftBank”) and LQUOM, Inc. (“LQUOM”) launched a trial to study the communication of entangled photons as a step toward realizing a quantum Internet. The field study will transmit entangled photons through optical fiber in the Tokyo Metropolitan Area. The optical fiber of this study links SoftBank’s headquarters and its data center in the Tokyo Metropolitan Area. LQUOM will integrate a quantum communication system with the field fiber. Accordingly, SoftBank and LQUOM will investigate quantum communication technology in a practical environment in the Tokyo Metropolitan Area.
SoftBank aims to realize a hybrid network that encompasses existing Internet and quantum Internet technologies as future infrastructure to support the quantum era. LQUOM has been developing quantum communication technologies with a view toward realizing a quantum Internet. SoftBank and LQUOM will investigate fundamental technologies for a quantum Internet, consider practical use cases for a quantum Internet, and contribute to advanced network infrastructure of the future.
A schematic illustration of a hybrid network encompassing the existing Internet and a quantum Internet
Background of this study
Quantum information science, including quantum computers, has seen accelerated development globally. Because existing Internet technologies are hardly able to support all functions of quantum information science, quantum Internet technology has been studied intensively. The quantum Internet is expected to open the door to distributed quantum computation, information-theoretically secure communication, quantum teleportation, and the accurate synchronization of clocks at distant sites.
Quantum entanglement plays a fundamental role in a quantum Internet. A photon is one physical system that can be the medium of quantum entanglement. An entangled photon has the advantage of communication through optical fiber. A quantum Internet aims to distribute entangled photons to distant sites.
The realization of a quantum Internet needs (i) a source of photons with entanglement, (ii) transmission of the entangled photons over optical fiber, and (iii) a quantum repeater system. Because quantum states are intrinsically unstable, long-distance quantum communication is a challenge to achieve. Thus, a quantum repeater system has attracted broad attention as a key technology for long-distance quantum communication.
Summary of the field study
Optical fiber infrastructure in a metropolitan area essentially receives environmental noise such as mechanical vibrations from subways and cars, wind, and temperature changes in day/night or over the seasons. How the field environment impacts the communication of entangled photons is of critical importance, and this needs to be addressed through investigation.
This field study experimentally investigates quantum communication in the Tokyo Metropolitan Area. LQUOM’s quantum communication system will be deployed to optical fiber between SoftBank’s headquarters and its data center in the Tokyo Metropolitan Area (the total length of the field fiber is 16 km). Firstly, both companies will study the environmental conditions of SoftBank’s network and its impact on the stability and phase change of entangled photons. Such an experimental analysis may contribute to the understanding of the technical problems of deploying quantum communication technology into field fiber. In the future, both companies plan to study the field deployment of a long-distance quantum communication system to be developed by LQUOM.
LQUOM is a quantum startup from Yokohama National University. LQUOM focuses on the development of quantum communication systems, including a quantum repeater, for realizing a quantum Internet. LQUOM has already cultivated the core technologies that are necessary for a quantum repeater system. In 2023, LQUOM raised funds for accelerating the development of a quantum repeater. (See also LQUOM’s website. https://lquom.com/)
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