Quantum communication
양자 통신
Communication that uses quantum properties so that anyone who eavesdrops leaves a trace.
Overview
A quantum state changes if someone looks at it. Quantum communication uses this property. The first use is quantum key distribution (QKD). The key that opens a code is sent on particles of light, so that if someone peeks along the way, the receiver can notice.
The weak point is distance. Light particles gradually disappear in an optical cable, so without relay devices along the way it is hard to go beyond a few hundred km. So people use satellites, or research repeaters that pass on quantum states. A quantum internet, which would link faraway quantum computers, is the next goal.
An everyday example
It is like putting a seal on a letter's envelope that changes color if someone opens it. It does not stop anyone from peeking, but it shows that someone did.
Why it matters
There are two ways to answer the threat quantum computers pose to today's encryption. One is post-quantum cryptography, built on new math problems. The other is quantum communication, which relies on the laws of physics. Quantum communication needs dedicated equipment and communication lines.
Also calledquantum cryptographic communication