STEM与日常科技·英语30篇（2）

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量子通信在防窃听上的直觉

Quantum communication encodes information in single photons — tiny particles of light — whose properties cannot be copied perfectly.
If an eavesdropper tries to measure a photon’s polarization, the act itself changes its state, leaving detectable errors.
Legitimate users compare a random subset of their shared bits over a public channel to spot unusual error rates.
High error rates signal possible spying, so they discard that key and try again — security is built into the protocol itself.
Unlike classical encryption, which relies on math problems being hard to solve, quantum security rests on physical laws.
No device, however advanced, can clone an unknown quantum state — this is the no-cloning theorem, proven and fundamental.
Current systems use fiber networks up to 100 km long or satellite links for longer distances, like China’s Micius mission.
Even if hackers store intercepted photons, they cannot decode them later — quantum keys offer ‘forward secrecy’ by design.
Commercial quantum networks already protect bank transfers and government documents in several countries today.
It’s not magic — it’s careful engineering guided by quantum mechanics to make interception physically obvious and futile.