Fermions do not travel together, theory proved

March 10, 2007

Fermions tend to avoid each other and cannot "travel" in close proximity. Demonstrated by a French team at the Institut d'optique (CNRS), this result is described in detail in the January 25, 2007 issue of Nature. It marks a major advance in our understanding of phenomena at a quantum scale.

For many years, the theory of quantum mechanics stipulated that certain particles, the fermions , were incapable of "travelling" in close proximity. For example, in a jet of identical particles, the theory supposed that the distance between them was always greater than a given value, called the "correlation length".

Scientists in the Charles Fabry Laboratory at the Institut d'optique, working with a team from the Free University in Amsterdam, have recently shown that this "anti-bunching" property, which it had never been possible to demonstrate hitherto, does indeed exist. It is as if the particles repel each other, even though interactions between them are negligible. In fact, this "anti-bunching" is due to quantum interferences which forbid the probability of finding two very close particles.

To arrive at this conclusion, the scientists compared the behaviour of fermions with that of bosons , under identical conditions. Amongst the latter, the same interferences led on the contrary to a "bunching" effect, and thus an increased probability of finding two particles together.
The experiments at the Institut d'optique were performed using the same system (which ensured identical conditions) on two helium isotopes.

In this situation, the scientists demonstrated the correlation length of fermions, which was close to a millimetre. This effect was anticipated, but its demonstration constitutes an advance in our ability to detect correlations between atoms, and thus a further step towards understanding the behaviour of matter at the quantum scale.

Citation: Comparison of the Hanbury Brown–Twiss effect for bosons and fermions, T. Jeltes, J. M. McNamara, W. Hogervorst, W. Vassen, V. Krachmalnicoff, M. Schellekens, A. Perrin, H. Chang, D. Boiron, A. Aspect & C. I. Westbrook. Nature, 2007, Vol. 445, No. 7126

Source: CNRS

Explore further: Researchers observe exotic quantum particle in bilayer graphene

Related Stories

Cold fermions keep distance from each other

January 4, 2016

Today, quantum optical experiments provide methods to prove the rules that have been thought of and pressed into elegant mathematical equations in those days. In this regard, scientists in the Quantum Many-Body Division of ...

Third research team close to creating Majorana fermion

March 16, 2012

(PhysOrg.com) -- Recently there has been a virtual explosion of research efforts aimed at creating the elusive Majorana fermion with different groups claiming to be near to creating them. First there was news that a team ...

Neutrons zero in on the elusive magnetic Majorana fermion

June 8, 2017

Neutron scattering has revealed in unprecedented detail new insights into the exotic magnetic behavior of a material that, with a fuller understanding, could pave the way for quantum calculations far beyond the limits of ...

Recommended for you

Star mergers: A new test of gravity, dark energy theories

December 18, 2017

When scientists recorded a rippling in space-time, followed within two seconds by an associated burst of light observed by dozens of telescopes around the globe, they had witnessed, for the first time, the explosive collision ...

Single-photon detector can count to four

December 15, 2017

Engineers have shown that a widely used method of detecting single photons can also count the presence of at least four photons at a time. The researchers say this discovery will unlock new capabilities in physics labs working ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.