Quantum Repeater Chain: Entanglement Swapping

Real quantum networks can't just copy a qubit down a wire — the no-cloning theorem forbids it, and photon loss kills direct transmission past a few tens of kilometers. This simulator builds a line of repeater nodes between Alice and Bob and runs the actual protocol used to bridge that gap: each elementary hop races to generate a heralded Bell pair, decoherence eats away at its fidelity while it waits in memory, and every repeater performs a Bell-state measurement to swap two short entangled links into one longer one. Tune the chain length, per-hop generation rate, swap success probability and memory coherence time to see how quantum-repeater networks trade distance for fidelity — and watch how often, and how cleanly, an end-to-end entangled pair actually reaches Bob.