High powered lasers can physically melt the security components of a hack proof quantum network to create a secret back door.
Quantum key distribution is supposed to be unhackable because any eavesdropping would disturb the delicate quantum states. Sub-nanosecond laser pulses can permanently damage the fiber-optic attenuators meant to protect the system. This damage creates a hidden channel where an attacker can monitor the data flow without the legitimate users ever noticing a change in signal quality. Security experts previously assumed these hardware components were passive and immune to such targeted physical attacks. This vulnerability means the next generation of global secure communications is only as strong as the physical heat resistance of its smallest glass parts.
Robustness of fiber-optic attenuators to 1061-nm sub-nanosecond pulsed laser radiation in quantum key distribution systems
arXiv · 2604.25620
The security of quantum key distribution (QKD) systems relies on the physical integrity of their components. While laser-damage attacks (LDAs) using high-power continuous-wave (cw) lasers have been well studied, the threat posed by pulsed lasers at alternative wavelengths remains underestimated. Here, we experimentally investigated the stability of four types of fiber-optic attenuators under exposure to sub-picosecond pulses at 1061 nm with average power reaching 1 W. Mechanical variable attenua