Quantum Zeno Effect — Frequent Measurement Freezes a Qubit

This simulator drives a qubit toward a full |0⟩ → |1⟩ transition with a Rabi field and lets you interrupt that drive with periodic projective measurements. A single Bloch-sphere arrow shows one representative trial resetting to |0⟩ (or occasionally snapping to |1⟩) at every measurement tick, while a 180-atom instanced ensemble runs the same process stochastically so you can watch the survival fraction track the closed-form prediction P_survive(N) = [cos²(π/2N)]^N in real time. Pack more measurements into the same window and the transition is visibly suppressed — the quantum Zeno effect, first confirmed experimentally with trapped ions by Itano et al. in 1990. Turn measurement off and the same drive instead produces ordinary, undamped Rabi oscillation, making the contrast direct rather than asserted.