# Three-user quantum-key experiment withstands 59.6 dB system loss

_Published Monday, September 21, 2026 at 12:08 PM EDT · Science, Security · Latest · Tier 2 — Notable_

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Researchers at Nanjing University experimentally generated a shared secure key for three users under total system loss of approximately 59.6 dB, compared with approximately 21.5 dB in the group's earlier measurement-device-independent conferencing experiment. The laboratory result was published in Physical Review Letters.

The protocol pairs single-photon detections recorded at different times instead of requiring simultaneous multiphoton events, improving how key rates scale as users and transmission losses increase. A shared measurement station can announce detections without being trusted. At the highest tested loss, however, the secure-key rate was approximately 4.470 × 10⁻⁹ bits per pulse, and practical intercity deployment remains future work.

## Sources

- [Phys.org](https://phys.org/news/2026-09-quantum-communication-protocol-enables-users.html)

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Canonical: https://techandbusiness.org/newswire/VLeI_wydwigwBduROJYZei
Published: 2026-09-21T16:08:02.517Z
Story chronology: 2026-09-21T16:00:01.000Z
Retrieved: 2026-09-21T18:19:20.455Z
Publisher: Tech & Business (techandbusiness.org)