Quantum Zeno Crossover — Bloch Phase-Space Portrait

The same exact two-level master equation behind the double-well Zeno/anti-Zeno crossover, drawn as a native 2D phase-space diagram instead of a 3D well: the population-difference/coherence vector (z, y) traces a spiral on a disk, decaying from the unit circle toward the origin at a rate that depends on the dephasing (measurement) rate γ. A second panel plots the analytic Kofman-Kurizki crossover curve Γ_eff(γ) — γ/2 in the anti-Zeno regime, collapsing toward 4J²/γ in the quantum Zeno regime — with a live marker showing exactly where your current γ sits on that curve.