Breakthrough Tracker record
Two independent teams operated thorium-229 nuclear-clock prototypes
Vienna- and Tsinghua-led teams independently stabilized continuous-wave lasers to the thorium-229 nuclear transition in calcium-fluoride crystals, making the nuclear resonance the feedback reference in operational prototype clocks.
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- Stable ID
physics-thorium-229-operational-nuclear-clocks-2026- Revision
physics-thorium-229-operational-nuclear-clocks-2026.v1- Field
- Physics · Nuclear metrology and precision tests of fundamental physics
- Evidence
- Tier 1 · Peer reviewed: Yes
- Record state
- Current · Peer-reviewed convergent demonstrations
- Last checked
AI role
No substantive AI role was disclosed in the inspected primary papers or specialist assessments.
Record details
- Problem or result
- Closed-loop operation of solid-state thorium-229 nuclear clocks
- Authors
- L. Toscani De Col, T. Riebner, I. Morawetz and collaborators; Beichen Huang, Gaowei Yan, Qi Xiao and collaborators
- Institutions
- TU Wien-led European collaboration; Tsinghua University-led Chinese collaboration
- Result date
- Both Nature papers published October 7, 2026
Why it matters
The paired demonstrations turn a long-standing nuclear-clock proposal into a reproducible clock architecture and create a new platform for precision tests of changing constants and ultralight dark matter.
Limits
Neither prototype is yet more precise than the best optical atomic clocks. Proposed orders-of-magnitude gains, compact deployment and stronger new-physics limits are future prospects rather than demonstrated capabilities.
Sources
- Primary: Vienna-led thorium-229 nuclear clock
- Independent primary: Tsinghua-led thorium-229 nuclear clock
- Independent specialist assessment: APS Physics on the two operational nuclear clocks
- Independent specialist assessment: Chemical & Engineering News on the first nuclear clocks
Correction and revision history
- 2026-10-19 — Added after primary-source, scope, status, AI-role and limitation review.
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