Jinan-1 (济南一号) quantum microsatellite

What it is

Jinan-1 carries a single optical payload: a decoy-state BB84 transmitter. The satellite prepares weak coherent pulses in one of four polarisation states, downlinks them through a tracking telescope to a ground station during an overhead pass, and performs sifting and basis reconciliation in real time on board. The ground station decodes the polarisation states on single-photon detectors and runs the rest of the QKD post-processing stack with the satellite acting as the BB84 sender. ^{Li et al. 2025}

The engineering departure from Micius is the platform itself. Where Micius was a ~640 kg science satellite with three optical payloads, Jinan-1 is a ~23 kg microsatellite with a single payload and real-time on-board sifting, designed to be replicated at constellation scale. The space segment connects to the terrestrial Jinan metropolitan fibre QKD network through ground stations operated by the Jinan Institute of Quantum Technology, extending the metro network's reach through trusted-node hops rather than end-to-end entanglement. ^{Li et al. 2025}

Verified claims

• Microsatellite bus, ~23 kg, ~500 km sun-synchronous LEO — launched 27 July 2022 on a Lijian-1 rocket from Taiyuan. ^{Li et al. 2025}
• Decoy-state BB84 source on the satellite — polarisation-encoded prepare-and-measure protocol; ground station performs the measurements. ^{Li et al. 2025}
• Real-time on-board key sifting — sifting and basis reconciliation run on the satellite during the pass rather than after downlink to a control centre. ^{Li et al. 2025}
• Satellite-to-ground QKD to multiple ground stations — including fixed stations in China and mobile ground stations; a 12,900 km path to a Stellenbosch ground station has been demonstrated as a southern-hemisphere first. ^{Li et al. 2025}
• Integration with the Jinan metropolitan QKD network — the satellite operates as the space segment of an integrated terrestrial-plus-space QKD network anchored on Jinan.

Things to note

• Prepare-and-measure, not entanglement-based. Jinan-1 carries a decoy-state BB84 source, not an on-board entangled-photon source — distinct from the Micius 2017 (1,200 km Bell pair distribution) and 2020 (1,120 km entanglement-based QKD) results.
• Free-space downlinks operate in the usual envelope. Clear-sky night passes over participating ground stations are the standard operating window; daylight operation imposes a rate penalty as it does on every other satellite-QKD platform.
• Cross-segment hops use the trusted-node model. Chaining the satellite with the Jinan metropolitan fibre network for keys between non-co-located endpoints relies on trusting each relay node, in line with the Beijing–Shanghai backbone.
• Engineering platform, not a new physics result. The contribution is small-bus, real-time, replicable at low unit cost — designed as a precursor to a constellation rather than a one-off science mission.
• Distinct mission from Micius. The two satellites share programme heritage and the Pan group but are separate platforms with separate payloads; reporting that conflates them is common.

Related entries

• Entanglement distribution — free-space optical alongside fibre and matter-qubit links, though Jinan-1 itself does not distribute entanglement.
• Micius satellite — the earlier, larger science platform with on-board entanglement source.
• Beijing–Shanghai QKD backbone — the terrestrial trunk that the Jinan space segment plugs into through the metropolitan network.
• Applications — QKD as the use case driving the satellite-QKD platforms.
• Links — the free-space loss budget that LEO downlinks have to close.
• Companies — the Chinese vendor ecosystem (QuantumCTek, JIQT and others) supplying ground-segment hardware.