B92 Protocol (2D): Two-State Quantum Key Distribution

This is the 2D companion to the 3D B92 quantum-key-distribution simulator, driven by the exact same event-by-event model: Alice encodes each bit into one of two non-orthogonal polarization states, Bob randomly picks a measurement basis for every incoming photon, and only the roughly one-in-four photons that yield a logically conclusive outcome are kept as sifted key bits. The channel diagram is now a flat, pannable and zoomable plane so you can follow many photons and the growing sifted-key grid at once. Flip on the intercept-resend eavesdropper to see how the no-cloning theorem forces Eve's own measurement to leak into the channel as a rising quantum bit error rate, the exact fingerprint Alice and Bob use to catch her.