Chinese scientists have set a new world record by achieving twin-field quantum key distribution (QKD) over a 1,002-kilometer fiber optic cable. This milestone represents a critical step towards future large-scale quantum networks.
Quantum key distribution is a key method in quantum communication, allowing two remote users to generate a shared secret key known only to them for encrypting and decrypting messages. However, the limitation of quantum signals being unable to be amplified and the decreasing channel capacity with increasing distance have posed significant challenges for practical implementation.
Previously, twin-field QKD had been demonstrated in laboratory settings using coiled fiber up to a distance of 830 kilometers.
In a study published in Physical Review Letters, researchers from institutions such as the University of Science and Technology of China, the Jinan Institute of Quantum Technology, and the Shanghai Institute of Microsystem and Information Technology revealed that they achieved a distribution distance of 1,002 kilometers with a secure key rate of 0.0034 bits per second.
During the experiment, the scientists developed a dual-band phase modulator and an ultra-low-noise superconducting nanowire single-photon detector to suppress system noise, which had hindered the generation of secure keys over long distances.
According to the University of Science and Technology of China, this work confirms the feasibility of twin-field QKD for very long distances and sheds light on potential advancements in long-distance quantum communication.
Long-distance quantum communication
Long-distance quantum communication refers to the transmission of quantum information over significant distances, typically using photons as carriers of quantum states. It is a field of research that aims to develop secure and efficient methods for transmitting quantum information between distant locations.
Quantum communication relies on the principles of quantum mechanics, which allows for the encoding, transmission, and decoding of information using quantum states. Unlike classical communication, where information is encoded in classical bits (0s and 1s), quantum communication utilizes quantum bits or qubits, which can exist in a superposition of both 0 and 1 states simultaneously.
One of the main applications of long-distance quantum communication is quantum key distribution (QKD), which enables the secure exchange of cryptographic keys between two remote parties. QKD uses the properties of quantum mechanics to detect any attempts at eavesdropping, ensuring the security of the transmitted keys.
Challenges in long-distance quantum communication include the preservation of quantum states over long distances, minimizing noise and loss in the transmission channel, and developing efficient quantum repeaters or amplifiers to extend the reach of quantum signals.
Cover Photo: During the 2021 Quantum Industry Conference held in Hefei, Anhui province, eastern China, a participant watches a video about the quantum metropolitan area network on September 18, 2021. (Du Yu/Xinhua)
Provided by Xinhua_TR.