BB84 Quantum Key Distribution — 2D Photon Channel Simulator

Watch the BB84 quantum key distribution protocol run photon by photon along a flat channel view: Alice fires single photons polarised in a randomly chosen basis toward Bob, who measures each one in his own random basis. Only photons where the two bases happen to match survive sifting into the shared secret key. Flip on the intercept-resend eavesdropper sitting mid-channel and watch the quantum bit error rate jump toward the textbook 25% — the disturbance her measurement necessarily introduces, and the reason BB84 lets two parties detect an eavesdropper instead of unknowingly leaking their key. A scrollable history strip and a live QBER trend sparkline let you review the whole run, not just the current moment.