Quantum-encrypted messages sent over long-distance cables are sensitive to low vibrations, suggesting a possible by-product of a future secure network


May 17, 2022

Building destroyed by an earthquake in Izmir, Turkey, in October 2020

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Quantum communication technology can also measure small vibrations in the ground, making it potentially useful for detecting earthquakes and landslides.

Quantum Key Distribution (QKD) uses certain photon properties – light particles – to encrypt data sent between two devices, making the system more secure than traditional encryption. If an eavesdropper tries to gain access to the encrypted data, the quantum state of the photons changes, which can be detected and the sender can choose to stop the transmission.

Jian-Wei Pan at the University of Science and Technology in China and his colleagues demonstrated a type of QKD called double-field QKD that uses the way single photons interfere with each other to encrypt data. They successfully sent encrypted data over a 658-kilometer cable with minimal data loss, one of the longest distances demonstrated by any QKD system.

The encrypted information is contained in a quantum property called the photon phase, which must be carefully measured along the length of the cable. Any disturbances in the environment, such as vibrations in the ground, also affect this phase and can be detected.

“For the first time, we have shown that a dual-field QKD system can both distribute quantum switches and detect ultra-long-range vibrations, which is a new mechanism, as far as we know,” says Pan.

Data transfer speeds need to be improved before the technology can be integrated into a large-scale quantum communication network. But if that happens in the future, the sensation of vibration could be a useful by-product of such a system, he said. Timothy Spiller at the University of York, UK.

An impressive aspect of the sensation of vibration is how accurately researchers can determine it along the length of the cable, he added. “They can identify vibrations on the fiber, but then they also use weather information to locate that vibration on the fiber to within a kilometer.

Reference journal: Physical examination letters, DOI: 10.1103 / PhysRevLett.128.180502

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