Category: fundamentals  |  Difficulty: beginner  |  Qubits: 3  |  Gates: 3  |  Depth: 3

The GHZ state generalises the Bell state to three (or more) qubits. It exhibits genuine multipartite entanglement: no qubit is separable from the others. It violates the Mermin inequality, ruling out local hidden variable theories. Measuring any one qubit immediately collapses all others to a definite state.

50% |000⟩, 50% |111⟩

The OpenQASM 2.0 circuit is in circuit.qasm.

OPENQASM 2.0;
include "qelib1.inc";
qreg q[3];
creg c[3];
h q[0];
cx q[0],q[1];
cx q[0],q[2];
measure q[0] -> c[0];
measure q[1] -> c[1];
measure q[2] -> c[2];

entanglement fundamentals ghz-state multipartite

• Greenberger, Horne, Zeilinger (1989). Going Beyond Bell's Theorem

MIT — part of the OpenQC Algorithm Catalog.