The study group proposed a new structure of the TF QKD network that is scaled up to the "two to many" network based on multiplexing, divided into polarization, time and wave length. Unlike the first demonstration by the University of Toronto, based on the ring structure of the network, the research group architecture is based on a star-shaped network. The quantum signal in the ring structure should pass through every user connected to the ring, but in the star structure it only passes through the centre, allowing for a more practical system with quantum key distribution.
To overcome the main barriers to implementation in the development of the TF QKD system, the command used a plug-and-play structure. A typical TF QKD system requires multiple control systems such as synchronizers, wave lengths, phases and polarization to maintain the indistinguishability of two quantum signals produced by different light sources from two users. While in the PnP TF QKD architecture developed by the KIST research group, the middle third party generates and transmits the initial signals to two users using one light source, and the signals return to the third party on a round trip.
Consequently, the polarization drift due to the dual beaming effect of the canal is automatically compensated and users have the same wave length; in addition, because two signals follow the same route in opposite directions, the timing of the arrival of the signals is naturally identical; as a result, only a phase controller is required to implement the research team architecture; based on architecture, the team successfully demonstrated the TF QKD network.
"This is an important research achievement showing the possibility of removing the two main obstacles to the commercialization of the AAC, and we have received the key technology leading the relevant research," said Sang-Wook Khan, head of the Quantum Information Centre.