Multiple choice
Run this circuit, then measure all 4 qubits at once. What is the probability of the joint outcome |0010⟩ (qubit 0 leftmost)?
const c = circuit(4); c.h(0); c.cx(0, 1); c.h(2); c.cx(2, 3); // Bell-state measurement on the repeater qubits: undo the entangler. c.cx(1, 2); c.h(1); // 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 c.measure(); return c;
Commit your prediction for P(|0010⟩) — then run it.