Multiple choice
This circuit prepares qubit 0 in some state. What expectation value ⟨X⟩ does it have along the Bloch X-axis?
const c = circuit(3); c.h(0); c.cx(0, 1); c.cx(0, 2); // encode |+_L> c.x(1); // injected bit-flip error on qubit 1 // Decode: run the encoder backwards (CNOT is its own inverse). c.cx(0, 1); c.cx(0, 2); // Coherent majority correction: flip qubit 0 iff both partners say "1". c.ccx(2, 1, 0); return c;
Commit your prediction for ⟨X⟩ of qubit 0 — then run it.