Entanglement
얽힘
The property that ties two qubits together like one, so measuring one also settles the state of the other.
Overview
Two entangled qubits stay paired even if you move them far apart. When you measure one and get a result, the result you will get from the other is already matched to it.
This does not mean you can send news faster than light. The result of each measurement is random, so you cannot send a message you choose with it alone. Entanglement is used in quantum computer calculations and in quantum communication and security.
An everyday example
Say you split a pair of gloves between two boxes and send them far apart. If you open one box and find the left glove, the other box holds the right one. Entanglement is stranger than this, because before you open the box, it is truly not settled which one it is.
Why it matters
A quantum computer needs its qubits entangled to show its full power. It is also the basis of quantum communication, which can tell when someone is eavesdropping.
Also calledquantum entanglement