Entanglement and quantum information
Can quantum teleportation run fast over city-scale fibre?
Open access · cc by · source: Europe PMC
Researchers teleported single-photon quantum states across a campus fibre network several times per second with fidelity well above what any classical method could reach.
Study at a glance
- Design
- Other — Three-station fibre teleportation experiment (Alice, Bob, Charlie) with a PPLN entangled-photon source, Bell-state measurement, active timing and polarisation feedback, and state tomography.
- N
- Physics experiment; results are photon coincidence counts, not a sample of units.
- Population
- Photonic time-bin qubits sent over deployed and spooled telecom fibre on a university campus
- Outcome
- Teleportation rate, teleportation fidelity (vs the classical limit), entanglement visibility and photon indistinguishability
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Teleportation ran at 7.1 ± 0.4 Hz over a total state-transfer distance of 64 km of fibre. The average fidelity measured by tomography was 86.4 ± 4.5%, and the decoy-state estimate for true single photons was at least 90.6 ± 2.6%, both above the classical limit of 2/3. Entanglement survived distribution, with two-photon interference visibilities of 94.3% and 93.5%.
Methodology
Alice encoded time-bin qubits in weak laser pulses; Bob held one photon of an entangled pair made in a lithium-niobate waveguide and sent the other to Charlie, who performed a Bell-state measurement on Alice's photon and Bob's partner photon. Active feedback kept photon arrival times and polarisations matched despite fibre drifts. They checked the entanglement first, measured Hong-Ou-Mandel interference, then teleported several input states and reconstructed Bob's states with tomography, using the decoy-state method to estimate single-photon performance.
Limitations
Alice used attenuated laser pulses rather than genuine single photons, so the headline single-photon fidelity is an estimate from the decoy-state method, not a direct measurement. Much of the fibre was spooled in the lab rather than deployed in the field, and the Charlie-to-Bob distance was short, so this is not a demonstration over long free-running city links. Fidelity is limited by multiphoton events and remaining photon distinguishability, and the superposition states were more degraded than the pole states. A rate of a few hertz is still far below what practical networks need.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
City-scale links work, but slowly and near thresholds.
Entanglement can be delivered across metropolitan distances: two NV-centre nodes about Delft-The Hague apart were heralded into entangled states (fidelity 0.534 in the fully heralded mode), and fibre teleportation over 64 km reached about 7 Hz with fidelity above the classical 2/3 limit.
Evidence for the claim as stated.
Rate versus fidelity: the NV link trades rate for fidelity (0.48 Hz postselected, about one per minute heralded at 0.534), while photonic teleportation runs faster but used attenuated laser pulses, estimating single-photon fidelity with decoy states.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Rate versus fidelity: the NV link trades rate for fidelity (0.48 Hz postselected, about one per minute heralded at 0.534), while photonic teleportation runs faster but used attenuated laser pulses, estimating single-photon fidelity with decoy states.
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Same topic cluster — not a recommendation engine.
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