const c = circuit(4);
// 1 & 2: two elementary Bell pairs
c.h(0); c.cx(0, 1);
c.h(2); c.cx(2, 3);
// 3: Bell-state measurement on the repeater qubits (inverse entangler)
c.cx(1, 2);
c.h(1);
// 4: feed-forward corrections onto Bob's qubit (deferred-measurement form)
c.cx(2, 3);   // X correction conditioned on q2
c.cz(1, 3);   // Z correction conditioned on q1
// 5
c.measure();
return c;