Biexciton Cascade Phase-Ring — Polarization Precession Diagram

A semiconductor quantum dot pumped into its biexciton state relaxes through a two-photon radiative cascade — XX→X, then X→0 — one of the leading solid-state routes to on-demand single photons and polarization-entangled photon pairs. This 2D companion drops the 3D flight animation and plots the same physics natively: a polarization phase ring where each cascade's final precession angle φ = δt_X/ħ is stamped as a permanent dot (building a live histogram of dephasing), a scrolling event timeline showing each dwell time and its gate accept/reject outcome, and the exact analytic gated-visibility curve V(δ) with your running measured correlation plotted against it. Switch between the H/V (energy) and D/A (diagonal) measurement bases, and drag the gate window to watch the ring's mismatch fraction shrink back toward zero as post-selection recovers high-fidelity entanglement.