Limits RegistryPUBLIC RECORD
Limits RegistryBy October 2017 China's Beijing–Shanghai quantum communication trunk line, about 2,000 km of fiber linking Beijing, Jinan, Hefei and Shanghai through 32 trusted relay nodes, was operational. Combined with the Micius satellite, it was later integrated into a 4,600 km space-to-ground network reported in Nature in 2021. Security depends on trusting each relay node.
The question, scope, and sources behind this Registry record.
By October 2017 China's Beijing–Shanghai quantum communication trunk line, about 2,000 km of fiber linking Beijing, Jinan, Hefei and Shanghai through 32 trusted relay nodes, was operational. Combined with the Micius satellite, it was later integrated into a 4,600 km space-to-ground network reported in Nature in 2021. Security depends on trusting each relay node.
The total fiber length of the longest terrestrial quantum-secured communication backbone, built from chained QKD links with trusted relay nodes.
Change a parameter to stress-test whether a proposed result is still inside the published specification. This is an audit aid, not a proof checker.
This record has no editable parameters. Read the formal question and assumptions before challenging it.
Current frontiers derived from accepted Claims.
An observed or demonstrated result; no opposing bound is implied.
The frontier is not sacred
Most progress starts with a disagreement that survives contact with evidence. If you can push the known lower bound up or pull the upper bound down, show us the work.
≥ when you have shown that at least this value is achievable.≤ when you have shown that anything above this value is impossible.No vibes. State the value, define the scope, and link the paper, proof, code, or reproduction that lets another person check it. Editors review every challenge before the public record changes.
Challenge this recordAssertions tied to evidence, attribution, and review.
The frontier as it changed over time.
Only accepted Claims matching the current specification contribute to the displayed bounds. Strict inequalities remain open; contradictory Claims require editorial review.
1 accepted Claim, with 1 linked evidence records.
Permanent ID limitsregistry.com/limits/LR-BEIJING-SHANGHAI-QKD-BACKBONE
No active verified bounties are linked to this Limit.
View verified bounty tracker ↗No accepted machine-checked reproductions are recorded for this Limit.
Limits Registry. LR-BEIJING-SHANGHAI-QKD-BACKBONE. Longest terrestrial quantum key distribution backbone (Beijing–Shanghai). 2026.