OPTAGE (Osaka City) and LQUOM (Yokohama City) are conducting a demonstration experiment that combines LQUOM’s quantum communication technology with Optage’s commercial optical fiber in central Osaka, with the aim of implementing long-distance quantum communications in society. 

The purpose of this demonstration experiment was to demonstrate phase stabilization technology for optical fibers, with the aim of realizing long-distance quantum communications using commercial optical fibers. In quantum communication, it is essential to transmit photons (single particles of light) with low noise through optical fibers.

In order to put the currently promising long-distance quantum communication methods into practical use, reducing phase fluctuations caused by fiber expansion and contraction is a technical challenge.
In this demonstration experiment, a commercial optical fiber was prepared in an environment in central Osaka, and a new phase stabilization method using space division multiplexing was used to demonstrate a significant reduction in phase noise.

Commercial optical fibers are expected to be affected by noise caused by environmental factors such as temperature, rain, wind, and trains and cars. For this reason, we also conducted research in anticipation of future practical applications, such as whether phase stabilization works over several days and whether the error rate of quantum communication is affected by the fiber installation environment.