Another record! Pan Jianwei and Xu Feihu's team achieves 100-trillion bit rate quantum key distribution

Quantum key distribution (QKD) can provide radically secure communications. Application-oriented, the secret key rate (SKR) is a key figure of merit for any QKD system. However, so far, the SKR has been limited to around a few megabits per second.

 

 

 

Recently, Pan Jianwei, Feihu Xu, and other researchers from Shanghai Institute of Microsystems, Jinan Institute of Quantum Technology, and Harbin Institute of Technology have collaborated with each other to realize real-time quantum key distribution at 100 megabits rate for the first time in the international arena by developing key technologies such as high-fidelity integrated photonics quantum state modulation and high count rate superconducting single photon detection, and the experimental results have improved the previous record of code-forming rate by an order of magnitude.

 

 

 

On March 14, the results were published online in Nature Photonics (2023).

 

 

 

 

 

Quantum key distribution (QKD) is based on the basic principles of quantum mechanics, which can achieve in principle unconditionally secure confidential communication. the way of QKD can be understood as adding an extra link in the network, and both sides verify through a password to ensure the security before transmitting the information.

 

 

 

China is currently the country with the most achievements in QKD network infrastructure construction in the world. The opening of the quantum metropolitan network (the connection of different regions and industry organizations within a city) opens the case of connection with the quantum backbone network (the connection across provinces and cities ) and the quantum local area network (the access of multiple terminals within one unit or one location), providing the necessary infrastructure for the next step of having more areas to access the wide range of applications brought by the confidential communication network.

 

 

 

Increasing the code rate of QKD plays a crucial role in its practicalization. High bit rates can provide services to more users and enable applications with high bandwidth requirements such as big data sharing and distributed storage encryption. Previously, the highest international real-time code rate was 10 Mb/s (under a 10 km standard fiber channel).

 

 

 

In order to achieve higher key rates, technical bottlenecks such as system transmitter, receiver and post-processing need to be solved.

 

 

 

At the transmitter side, high code rate QKD requires high fidelity quantum state modulation, however, existing QKD systems generate high BER under high speed modulation; at the receiver side, single photon detectors with both high efficiency and high count rate capability are indispensable. Superconducting nanowire single photon detectors (SNSPD) have the advantages of high efficiency and low noise, but their count rate is usually limited by long recovery time.

 

 

 

This time, the research group of Jianwei Pan and Feihu Xu at the Institute of Quantum Information and Quantum Science and Technology Innovation, CAS has developed an integrated photonic on-chip high-speed high-fidelity polarization state modulation technique with a system re-frequency of 2.5 GHz and a quantum bit error rate better than 0.35%; combined with the newly developed eight-pixel SNSPD by Lixing You's group at the Shanghai Institute of Microsystems, CAS, the high count rate and high efficiency single photon detection has been achieved at At the same time, the research group has developed polarization feedback control and high-speed post-processing modules.

 

 

 

 

Diagram of high code-rate quantum key distribution device

 

 

 

 

Comparison of quantum key distribution code-forming rate

 

 

 

Based on the above technical breakthroughs, the research team achieved a key rate of 115.8 Mb/s in a 10 km standard fiber channel, which is about one order of magnitude higher than the previous record; the system operated stably for more than 50 hours, and the code rate exceeded 200 b/s at a transmission distance of 328 km.

 

 

 

The above research results show that QKD can realize real-time key distribution at 100 Mbit rate to meet the demand of high-bandwidth communication, which is of great significance to the future large-scale practical application of quantum communication.

 

 

 

Reference links：

 

[1] High-rate quantum key distribution exceeding 110 Mb s-1 | Nature Photonics

 

[2] Institute of Quantum Information and Quantum Science and Technology Innovation, Chinese Academy of Sciences, realizes 100 Mbit s-1 quantum key distribution (qq.com)