Quantum Internet Buffer Scheduler — 2D

Link Generation

Entanglement rate (per link) 2.0 Hz

Memory coherence T₂ 1.5 s

Buffer size (slots / side) 4

Scheduling Policy (displayed)

Displayed Policy — Live Readouts

Throughput

0.0 /s

Avg fidelity

–

Drop rate

How it works

A quantum internet cannot copy or amplify a qubit (no-cloning), so a repeater node must hold entangled halves in quantum memory until a matching partner from the other link arrives, then perform an entanglement swap (a joint Bell-state measurement) to stitch the two short links into one long-distance entangled pair.

Fidelity while stored:  F(t) = F₀ · exp(−t / T₂)
Delivered fidelity:     F_out ≈ F_L · F_R · η_swap
Decohered if:           F(t) < 0.5  → discarded, counts as a drop

Entanglement rate — each link heralds a fresh entangled pair into an empty buffer slot following a Poisson process. Real hardware: SPDC sources or atom-photon interfaces.
Memory coherence T₂ — how fast a stored qubit's fidelity decays exponentially while it waits for its partner. Short T₂ means most pairs decohere before a swap is possible.
Buffer size — slots per side. A full buffer forces new arrivals to be dropped (overflow) — the resource-contention side of quantum network architecture, distinct from the swap physics itself.
Scheduling policy — oldest-first serves the longest-waiting pair (fair, but it may already be low-fidelity); max-fidelity-first always swaps the freshest available pair (higher average output fidelity, but old pairs can starve and decohere anyway); random picks uniformly and sits between the two. All three run simultaneously on independent buffers fed by the same arrival stream below, so the bar chart is a genuine measured comparison, not a guess.

This scheduling problem — not the swap operation itself — is one of the open engineering challenges of a real quantum internet: memory is scarce and short-lived, so the network layer must decide who gets served before the qubits vanish.

Link A memoryRepeater nodeLink B memory

High fidelity (fresh) Mid fidelity (aging) Near decoherence

Avg delivered fidelity by policy (live, same arrival stream)