Direct photon
Repeater photon
Repeater station (swap)
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This scene lays two long-distance quantum links side by side over identical real fiber-loss physics. The direct channel fires single photons the full distance L; each one's fate is decided by the genuine exponential transmission law T(L)=10^(−αL/10), so it visibly fades and disappears along the way for anything beyond a modest range — and because the no-cloning theorem forbids copying an unknown quantum state, there is no way to "amplify" it back to strength the way a classical optical repeater would. The parallel repeater channel instead splits the same distance into short hops, generates entanglement independently across each one, and splices them together with entanglement-swap events at every station — never cloning the state, only combining independently-generated pairs. Tune the distance, fiber loss, repeater spacing and swap efficiency and watch the two live arrival counters diverge: the direct channel's throughput collapses exponentially with distance while the repeater channel keeps delivering, which is exactly why real long-haul quantum networks are engineered as repeater chains.