First thorium nuclear clocks begin ticking in Vienna and Beijing

Overview

Updated 1 hour ago

For 70 years, the world's most precise clocks have counted the vibrations of electrons orbiting an atom. In early October 2026, two teams — one in Vienna, one in Beijing — unveiled the first clocks that read time from the ticking of a thorium nucleus instead.

Neither clock is the most accurate timepiece yet; the best atomic clocks are about 10,000 times more stable. But nuclear clocks are built from crystals, which makes them far more portable and durable, and their nuclei are a fresh probe for dark matter and the forces binding the atom's core.

Why it matters

Working nuclear clocks could surpass atomic clocks in precision and portability, improving GPS and enabling a lab-scale search for dark matter.

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Key Indicators

1 sec in 30 million years

Demonstrated precision

Both clocks hold time to about 10⁻¹⁵, an error of roughly one second every 30 million years.

Working clock prototypes

One self-stabilizing clock in Vienna, one in Beijing — the first two nuclear clocks ever built.

10,000x

Gap to best atomic clocks

The leading optical atomic clocks are roughly 10,000 times more reliable than the new nuclear prototypes.

~6x

China's stability edge

The Tsinghua clock proved about six times more stable than the Vienna clock over a day, per the Nature papers.

Voices

Curated perspectives — historical figures and your fellow readers.

Ever wondered what historical figures would say about today's headlines?

People Involved

Thorsten Schumm

Professor, Institute of Atomic and Subatomic Physics, TU Wien

Leads the team behind the first self-stabilizing nuclear clock

Ding Shiqian

Associate professor, Department of Physics, Tsinghua University

Leads the Chinese team that built one of the first two nuclear clocks

Ekkehard Peik

Physicist, PTB (Germany's national metrology institute)

Co-originator of the thorium-229 nuclear clock concept

Organizations Involved

Vienna University of Technology (TU Wien)

Research university

Built the first self-stabilizing nuclear clock

Public research university in Vienna and home of the first self-stabilizing nuclear clock.

PTB (Physikalisch-Technische Bundesanstalt)

National metrology institute

Co-developer of the nuclear clock concept and laser excitation

Germany's national metrology institute, headquartered in Braunschweig.

Tsinghua University

Research university

Built one of the first two nuclear clocks

Elite research university in Beijing whose physics team built one of the first two nuclear clocks.

Timeline

April 2024 October 2026

5 events Latest: Today

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October 2026
Xinhua details China's nuclear clock
Today News

Xinhua reports China's clock details, including its 148-nanometer vacuum-ultraviolet laser and thorium crystal.
Today
Nature publishes first nuclear clock papers
Publication

Both teams' papers appear in Nature; Vienna's clock is the first self-stabilizing nuclear timepiece.
3 days ago
June 2026
Chinese nuclear clock preprint hits arXiv
Publication

Tsinghua team posts its independent thorium-229 clock results to arXiv.
June 7th, 2026
European nuclear clock preprint posted
Publication

Vienna team posts its nuclear clock results to the preprint server ahead of journal publication.
June 3rd, 2026
April 2024
Laser excites thorium nucleus for first time
Breakthrough

TU Wien and PTB teams drive thorium-229's nuclear transition with a laser, enabling nuclear clocks.
April 2024

Scenarios

Nuclear clock breaks atomic clock precision record

Possible Resolves by Q2 2030

Discussed by: Thorsten Schumm, Ekkehard Peik, and the two clock teams; Scientific American

The clock teams say the technical limits are now clear: stronger lasers and better thorium crystals should push stability far beyond today's level. Schumm and Peik both expect nuclear clocks to approach or pass the best optical atomic clocks, though neither gives a firm date. Improvements will be steady and measurable, making a record a matter of engineering time rather than new physics.

Portable nuclear clocks reach commercial devices

Possible Resolves by End of 2030

Discussed by: Shiqian Ding; Scientific American; Thorsten Schumm

Crystal-based nuclear clocks resist vibration and need no extreme cooling, unlike clocks that trap atoms in vacuum. Schumm says companies are already developing crystal nuclear clocks commercially. A compact, fieldable clock would upgrade navigation satellites, deep-space probes, and secure communications with timekeeping that today only fills national laboratories.

Nuclear clock catches a dark matter signal

Unlikely Resolves by End of 2028

Discussed by: Vienna team's first search (published in Nature); Gilad Perez, Weizmann Institute

The Vienna clock's first test searched for couplings between the thorium-229 nucleus and certain dark matter candidates and found nothing. The nucleus's energy structure makes it a uniquely sensitive laboratory probe. A detection would be the first time dark matter was caught by a clock, and the search will continue as the instruments improve.

Historical Context

2 moments from history that rhyme with this story — and how they unfolded.

1955

First cesium atomic clock (1955)

In 1955, Louis Essen and Jack Parry built the first accurate cesium atomic clock at Britain's National Physical Laboratory, using the vibration of cesium atoms to keep time far more steadily than any mechanical clock before it.

Then

Cesium clocks spread rapidly; by 1967 the world redefined the second in terms of the cesium atom, a standard still in use.

Now

Atomic clocks became the backbone of GPS, telecommunications, and scientific measurement worldwide.

Why this matters now

Like the first cesium clock, today's nuclear clocks are prototype proof that a new timekeeping mechanism works — years from beating existing standards but with a clear path to doing so.

2001-2005

Optical lattice clocks (2003)

In 2003, Japanese physicist Hidetoshi Katori demonstrated the optical lattice clock, trapping atoms in a grid of laser light to count their vibrations at far higher frequencies than cesium clocks could reach.

Then

Optical clocks gradually overtook cesium standards in precision over the following two decades.

Now

They now define the frontier of timekeeping, gaining or losing a second every 40 billion years — the benchmark the new nuclear clocks must beat.

Why this matters now

The roughly two-decade trajectory from first demonstration to world records in optical clocks shows the likely path and timeline for nuclear clocks.