W state

From Wikipedia, the free encyclopedia

The W state is an entangled quantum state that, for three qubits, has the following shape: $|W\rangle = \frac{1}{\sqrt{3}}(|001\rangle + |010\rangle + |100\rangle).$ Generally, for n qubits, this is a quantum superpostion with equal expansion coefficients of all possible pure states in which one of the qubits in in an "excited state" $|1\rangle)$ , while all other ones are in the "ground state" $|0\rangle).$

[edit] Properties

An interesting property of the W state is that it can leave an entangled 2-qubit system after one of its qubits is lost. This is robust entanglement contrary to the Greenberger-Horne-Zeilinger state which is fragile.