Researchers are developing key technology for the commercialization of quantum cryptography

KIST develops key technology for the commercialization of quantum cryptography

2:N TF QKD network structure. Photo credit: Korea Institute of Science and Technology

In modern cryptosystems, users generate public and private keys that guarantee security based on computational complexity and use them to encrypt and decrypt information. Recently, however, modern public-key cryptosystems have been exposed to potential security vulnerabilities compared to quantum computers with large computing power. Quantum cryptosystems have received much attention as a solution. They use quantum keys that guarantee security based on quantum physics and not computational complexity; this also makes them secure against quantum computers. Therefore, it is expected that quantum cryptosystems will replace modern cryptosystems.

Quantum key distribution (QKD) is the most important technology for realizing quantum cryptosystems. Two main technical issues should be addressed in order to commercialize QKD. One is the communication distance and the other is the extension from one-to-one (1:1) communication to one-to-many (1:N) or many-to-many (N:N) network Communication.

Twin-Field (TF) QKD, announced in 2018, is a long-haul protocol that can dramatically increase the communication distance of QKD systems. In TF QKD, two users can share a key by transmitting quantum signals to an intermediary third party used for measurement. Faced with the inevitable channel loss, this architecture allows users to increase the communication distance. However, despite its innovative power, it has only been experimentally demonstrated by a few global QKD leadership groups due to the significant difficulty of system implementation, and research on the TF-QKD network is still insufficient.

The Korea Institute of Science and Technology (KIST, Director Seok-jin Yoon) announced that its research team, the Center for Quantum Information, led by Director Sang-Wook Han, has achieved an experimental demonstration of a practical TF-QKD network is. This is the second experimental demonstration of the TF QKD network in the world after the University of Toronto in Canada.

In their study published in npj quantum informationthe research team proposed a new TF-QKD network structure scalable to a two-to-many (2:N) network based on polarization, time and wavelength division multiplexing. In contrast to 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 the star structure only needs to go through the middle, making it possible to implement a more practical QKD system.

KIST develops key technology for the commercialization of quantum cryptography

experimental chart. Photo credit: Korea Institute of Science and Technology

In addition, the team adopted a plug-and-play (PnP) structure to overcome the key implementation obstacles in the development of the TF-QKD system. A conventional TF-QKD system requires many control systemsB. Timing, wavelength, phase and polarization controls to maintain indistinguishability of two quantum signals emitted by two different light sources of two users. While in the PnP-TF-QKD architecture developed by the KIST research team, the middle third generates the initial signals and transmits them to both users with a single light source, and the signals return to the third through a round-trip path. Therefore, the polarization drift due to the birefringence effect of the channel is automatically compensated, and the users are basically the same wavelength. In addition, due to the two signals passing through the same route in opposite directions, the arrival times of the signals are of course identical. As a result, only one phase controller is required to implement the research team’s architecture. Based on the architecture, the team successfully performed an experimental demonstration of a TF-QKD network.

“It is a significant research achievement that demonstrates the possibility of solving the two major obstacles to the commercialization of QKD, and we have gained a key technology that is spearheading the relevant research,” said Sang-Wook Han, head of the Quantum Information Center.

Secure communication with light particles that bypasses polarization dependency

More information:
Chang Hoon Park et al., Configuration of a 2 × N dual-field quantum key distribution network based on polarization, wavelength and time-division multiplexing, npj quantum information (2022). DOI: 10.1038/s41534-022-00558-8

Provided by the National Research Council of Science & Technology

Citation: Researchers Create Key Technology for Quantum Cryptography Commercialization (2022, July 22) Retrieved July 23, 2022 from

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