Swansea Physicists’ historic anti-matter breakthrough

Scientists collaborating in a major international experiment to study anti-matter closely for the first time have made a significant breakthrough – the first direct measurement of any kind on a pure anti-matter atom.

Prof Mike CharltonThe group, which includes Physicists from Swansea University’s College of Science, has published their latest findings online in the leading science journal Nature.

Professor Mike Charlton, who leads the Swansea team working on the ALPHA experiment at CERN, the European Organisation for Nuclear Research in Geneva, Switzerland, said their achievement marked the beginning of an exciting new phase in scientific discovery. 

“Our anti-hydrogen measurements are an historic achievement in anti-matter science,” said Professor Charlton. “They are both the culmination of many years of effort for the Swansea team, and a launchpad for a bright future studying the properties of atoms made entirely from anti-matter."

Fellow Swansea physicist Dr Niels Madsen stressed the ALPHA team had achieved this breakthrough with a very small sample, which gives the team great encouragement for their future experiments, when they aim to trap more.

“Anti-atoms are currently only trapped one at a time, which gives about one to work with every 20 minutes,” said Dr Madsen.

"This is the first direct measurement of any internal state in an anti-atom. It is fantastic and a true breakthrough that we can do measurements of this kind with such a rare species.”

The aim of the ALPHA experiment at CERN, which brings together scientists from eight countries including the UK, USA, Canada, and Japan, is detailed studies of anti-hydrogen atoms – the anti-matter counterpart of the simplest atom, hydrogen.

By precise comparisons of hydrogen and anti-hydrogen, the ALPHA team hope to study fundamental symmetries between matter and antimatter and cast light on the puzzling absence of bulk anti-matter in universe today.


Swansea has a total of 10 authors on the Nature paper – the largest representation from a single institution – and the project involves academics staff Professor Mike Charlton, Dr Niels Madsen, Dr Dirk Peter van der Werf, and Dr Stefan Eriksson; postdoctoral researchers Dr Will Bertsche (who now has a lectureship at Manchester University) and Dr Aled Isaac; research students Adam Deller and Andrew Humphries; and undergraduate students Silvia Napoli and Caroline Shields, who worked on the project at CERN last summer.

The team’s work is supported by the UK’s Engineering and Physical Sciences Research Council (EPSRC), the Leverhulme Trust and the Royal Society.


Scientists have been able to undertake the controlled production of anti-hydrogen atoms in the laboratory for nearly a decade – a breakthrough which Swansea University physicists played a key role in as part of the ATHENA project at CERN, the first experiment to produce copious amounts of cold anti-hydrogen.

But as anti-matter particles are instantly annihilated when they come into contact with matter, it has not previously been feasible to study anti-hydrogen atoms in any detail.

The ALPHA team has developed techniques that not only cool and slow down the anti-particles that make up anti-hydrogen and gently mix them to produce anti-hydrogen atoms, but also trap some of the anti-atoms for long enough so that they can be studied. 

A key advancement has been a new method that allows the cooled anti-particles to be brought together in a way that ensures the anti-hydrogen atoms are cold enough to be trapped. 

In this phase of the experiment – the first direct measurement of any kind on a pure anti-matter atom – the team intentionally manipulated the internal spin state of anti-hydrogen atoms, to induce magnetic resonance transitions between hyperfine levels of the positronic ground state.

Resonant microwave radiation was used to flip the spin of the positron in anti-hydrogen atoms, which were magnetically trapped in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap.

The team were then able to look for evidence of resonant interaction, by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance.  

In a further tour-de-force, the Liverpool developed detector was used to identify the resonant ejection of individual anti-atoms, to form a complete picture of the destiny of each anti-atom in the experiment.

This action represents the first resonant, spectroscopic measurement of any kind to be performed on a pure anti-matter atom.

To view the team’s paper, “Resonant Quantum Transitions in Trapped Anti-hydrogen Atoms”, visit www.nature.com

This news item was posted by Bethan Evans, Swansea University Public Relations Office, Tel: 01792 295049, or email: b.w.evans@swansea.ac.uk.