Physicists have built a commercial network with quantum cryptography

The research team proposed a new TF QKD network structure that scales to a two-to-many (2:N) network on

based on division multiplexingpolarization, time and wavelength. Unlike the University of Toronto's first demonstration, which was based on a ring network structure, the research team's architecture is based on a star network. The quantum signal in a ring structure must pass through each user connected to the ring, but in a star structure it only passes through the center, allowing for a more practical quantum key distribution system.

To overcome the main obstacles to implementationThe team adopted a plug-and-play (PnP) design when developing the TF QKD system. A conventional TF QKD system requires multiple control systems, such as timing, wavelength, phase, and polarization controllers, to maintain the indistinguishability of two quantum signals emitted by two users' different light sources. 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 at once using one light source, and the signals are returned to the third party by making a circular journey. 

QRC network architecture

Therefore, the polarization drift due to the effectchannel birefringence is automatically compensated, and users have fundamentally the same wavelength. Also, because the two signals travel the same route in opposite directions, the arrival times of the signals are naturally identical. As a result, only a phase controller is required to implement the research team architecture. Based on the architecture, the team successfully conducted a pilot demonstration of the TF QKD network.

"This is an important research achievement,demonstrating the possibility of removing two major obstacles to the commercialization of QKD, and we have received a key technology leading relevant research,” said Sang-Vuk Khan, head of the Center for Quantum Information.

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