Quantum Clock Synchronization

Network Delay

Unknown asymmetry Δ 150 ns

Channel jitter 40 ns

Run Sync Rounds

Achieved Sync Error

Classical (NTP)

— ns

Quantum

— ns

Rounds used

Quantum advantage

1.0×

Δ sets a hidden, unknown asymmetric one-way delay between the two sites — like different fibre-path lengths or router queueing. Classical NTP-style sync assumes the path is symmetric and cannot fully correct for it. The entanglement-based protocol distributes correlated photon pairs whose timing correlation is fixed at creation, letting the correction cancel most of that same asymmetry.

How the two protocols work

Classical: a round-trip ping estimates offset assuming equal forward/back delay. Bias ≈ Δ/2, no matter how many rounds run — only the random jitter averages down (∝ 1/√N).
Quantum: each round sends one entangled pair, one photon per site. Arrival-time correlations let the sites cancel the asymmetric bias directly, so error falls faster with N (approaching the Heisenberg-like 1/N scaling) instead of hitting a floor.

Classical packet (round-trip) Entangled photon pair

Classical error Quantum error