// H on qubit 0 makes (|0> + |1>)/sqrt2 on the first qubit;
// CNOT(0->1) and CNOT(0->2) entangle the rest, giving (|000> + |111>)/sqrt2.
const c = circuit(3);
c.h(0);
c.cx(0, 1);
c.cx(0, 2);
return c;