Quantum key distribution

Can secret messages be intercepted without anyone noticing?

Imagine Alice wants to send Bob a secret message, but she's worried someone might intercept it and read it.

Alice and Bob can use a special method that makes eavesdropping obvious, so if someone tries to spy on their secret message, Alice and Bob will know.

Example

Alice sends Bob a message encoded in a quantum state. If Eve tries to read it, the quantum state changes, alerting Alice and Bob.

Remember this

Quantum entanglement ensures that any eavesdropping attempt will disturb the quantum state, making interception detectable.

Text adapted from Wikipedia, licensed under CC BY-SA 4.0.

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